Fitter content - 2nd sem-TT.p65

[Audio] FITTER NSQF LEVEL - 5 1st Year (Volume II of II) TRADE THEORY NIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMINIMIHPBW SECTOR: Production & Manufacturing DIRECTORATE GENERAL OF TRAINING MINISTRY OF SKILL DEVELOPMENT & ENTREPRENEURSHIP GOVERNMENT OF INDIA NATIONAL INSTRUCTIONAL MEDIA INSTITUTE, CHENNAI Post Box No. 3142, CTI Campus, Guindy, Chennai - 600 032 (i) Copyright Free Under CC BY Licence.

[Audio] Sector : Production & Manufacturing Duration : 2 - Years Trade : Fitter 1st Year (Volume II of II) - Trade Theory - NSQF level 5 First Edition : December 2018, Copies : 10,000 Rs.215/All rights reserved. No part of this publication can be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording or any information storage and retrieval system, without permission in writing from the National Instructional Media Institute, Chennai. Published by: NATIONAL INSTRUCTIONAL MEDIA INSTITUTE P. B. No.3142, CTI Campus, Guindy Industrial Estate, Guindy, Chennai - 600 032. Phone : 044 - 2250 0248, 2250 0657, 2250 2421 Fax : 91 - 44 - 2250 0791 email : [email protected], [email protected] Website: www.nimi.gov.in (ii) Copyright Free Under CC BY Licence.

[Audio] FOREWORD The Government of India has set an ambitious target of imparting skills to 30 crores people, one out of every four Indians, by 2020 to help them secure jobs as part of the National Skills Development Policy. Industrial Training Institutes (ITIs) play a vital role in this process especially in terms of providing skilled manpower. Keeping this in mind, and for providing the current industry relevant skill training to Trainees, ITI syllabus has been recently updated with the help of Mentor Councils comprising various stakeholder's viz. Industries, Entrepreneurs, Academicians and representatives from ITIs. The National Instructional Media Institute (NIMI), Chennai has now come up with instructional material to suit the revised curriculum for Fitter 1st Year Trade Theory NSQF Level - 5. The NSQF Level - 5 Trade Theory will help the trainees to get an international equivalency standard where their skill proficiency and competency will be duly recognized across the globe and this will also increase the scope of recognition of prior learning. NSQF Level - 5 trainees will also get the opportunities to promote life long learning and skill development. I have no doubt that with NSQF Level - 5 the trainers and trainees of ITIs, and all stakeholders will derive maximum benefits from these IMPs and that NIMI's effort will go a long way in improving the quality of Vocational training in the country. The Executive Director & Staff of NIMI and members of Media Development Committee deserve appreciation for their contribution in bringing out this publication. Jai Hind RAJESH AGGARWAL Director General/ Addl. Secretary Ministry of Skill Development & Entrepreneurship, Government of India. New Delhi - 110 001 (iii) Copyright Free Under CC BY Licence.

[Audio] PREFACE The National Instructional Media Institute (NIMI) was established in 1986 at Chennai by then Directorate General of Employment and Training (D.G.E & T), Ministry of Labour and Employment, (now under Directorate General of Training, Ministry of Skill Development and Entrepreneurship) Government of India, with technical assistance from the Govt. of the Federal Republic of Germany. The prime objective of this institute is to develop and provide instructional materials for various trades as per the prescribed syllabi under the Craftsman and Apprenticeship Training Schemes. The instructional materials are created keeping in mind, the main objective of Vocational Training under NCVT/NAC in India, which is to help an individual to master skills to do a job. The instructional materials are generated in the form of Instructional Media Packages (IMPs). An IMP consists of Theory book, Practical book, Test and Assignment book, Instructor Guide, Audio Visual Aid (Wall charts and Transparencies) and other support materials. The trade practical book consists of series of exercises to be completed by the trainees in the workshop. These exercises are designed to ensure that all the skills in the prescribed syllabus are covered. The trade theory book provides related theoretical knowledge required to enable the trainee to do a job. The test and assignments will enable the instructor to give assignments for the evaluation of the performance of a trainee. The wall charts and transparencies are unique, as they not only help the instructor to effectively present a topic but also help him to assess the trainee's understanding. The instructor guide enables the instructor to plan his schedule of instruction, plan the raw material requirements, day to day lessons and demonstrations. In order to perform the skills in a productive manner instructional videos are embedded in QR code of the exercise in this instructional material so as to integrate the skill learning with the procedural practical steps given in the exercise. The instructional videos will improve the quality of standard on practical training and will motivate the trainees to focus and perform the skill seamlessly. IMPs also deals with the complex skills required to be developed for effective team work. Necessary care has also been taken to include important skill areas of allied trades as prescribed in the syllabus. The availability of a complete Instructional Media Package in an institute helps both the trainer and management to impart effective training. The IMPs are the outcome of collective efforts of the staff members of NIMI and the members of the Media Development Committees specially drawn from Public and Private sector industries, various training institutes under the Directorate General of Training (DGT), Government and Private ITIs. NIMI would like to take this opportunity to convey sincere thanks to the Directors of Employment & Training of various State Governments, Training Departments of Industries both in the Public and Private sectors, Officers of DGT and DGT field institutes, proof readers, individual media developers and coordinators, but for whose active support NIMI would not have been able to bring out this materials. R. P. DHINGRA Chennai - 600 032 EXECUTIVE DIRECTOR (iv) Copyright Free Under CC BY Licence.

[Audio] ACKNOWLEDGEMENT National Instructional Media Institute (NIMI) sincerely acknowledges with thanks for the co-operation and contribution extended by the following Media Developers and their sponsoring organisations to bring out this Instructional Material (Trade Theory) for the trade of Fitter under Production & Manufacturing Sector for ITIs. MEDIA DEVELOPMENT COMMITTEE MEMBERS Shri. M. Sampath _ Training officer (Retd.) CTI, Chennai-32. Shri. M. Sangarapandian _ Training officer (Retd.) CTI, Chennai - 32 Shri. K. Kesavan _ Asst. App. Advisor Junior (Retd) DET, Tamilnadu Shri. C.C. Subramanian _ Training officer (Retd.) Balamandir PHM ITI, Chennai - 17 Shri. A. Stephen _ Instructor, St. John's ITI Manapparai Trichy District - 621 307 Shri. A. Chandraprakash _ Vocational Instructor, NSTI, Hyderabad Shri. K.B. Shivaramu _ Junior Training officer Government ITI, Mysore - 570007 Shri. D.C. Nataraja _ Junior Training officer Government ITI, Mysore - 570007 Shri. Milind Rasu _ Instructor, Government ITI Aliganj, Lucknow Shri. K. Srinivasa Rao _ Joint Director, Co-ordinator, NIMI, Chennai - 32 Shri. G. Michael Johny _ Assistant Manager, Co-ordinator, NIMI, Chennai - 32 NIMI records its appreciation for the Data Entry, CAD, DTP operators for their excellent and devoted services in the process of development of this Instructional Material. NIMI also acknowledges with thanks the invaluable efforts rendered by all other NIMI staff who have contributed towards the development of this Instructional Material. NIMI is also grateful to everyone who has directly or indirectly helped in developing this Instructional Material. (v) Copyright Free Under CC BY Licence.

[Audio] INTRODUCTION TRADE THEORY The manual of trade theory consists of theoretical information for the Second Semester Course of the Fitter Trade. The contents are sequenced according to the practical exercise contained in NSQF LEVEL - 5 syallabus on Trade practical. Attempt has been made to relate the theoretical aspects with the skill covered in each exercise to the extent possible. This correlation is maintained to help the trainees to develop the perceptional capabilities for performing the skills. Module 1 Drilling 150 Hrs Module 2 Fitting assembly 150 Hrs Module 3 Turning 125 Hrs Module 4 Basic Maintenance 75 Hrs Module 5 In-plant training/Project work 50 Hrs Total 550 Hrs The Trade Theory has to be taught and learnt along with the corresponding exercise contained in the manual on trade practical. The indications about the corresponding practical exercises are given in every sheet of this manual. It will be preferable to teach/learn the trade theory connected to each exercise atleast one class before performing the related skills in the shop floor. The trade theory is to be treated as an integrated part of each exercise. The material is not for the purpose of self learning and should be considered as supplementary to class room instruction. TRADE PRACTICAL The trade practical manual is intented to be used in practical workshop . It consists of a series of practical exercises to be completed by the trainees during the Second Semester Course of the Fitter Trade supplemented and supported by instructions/ informations to assist in performing the exercises. These exercises are designed to ensure that all the skills in compliance with NSQF LEVEL - 5 syllabus are covered. The manual is divided into five modules. The distribution of time for the practical in the five modules are given below. The skill training in the shop floor is planned through a series of practical exercises centred around some practical object. However, there are few instances where the individual exercise does not form a part of project. While developing the practical manual a sincere effort was made to prepare each exercise which will be easy to understand and carry out even by below average trainee. However the development team accept that there is a scope for further improvement. NIMI looks forward to the suggestions from the experienced training faculty for improving the manual. (vi) Copyright Free Under CC BY Licence.

[Audio] CONTENTS Lesson No. Title of the Lesson Page No. Module 1: Drilling 2.1.61 Drills 1 2.1.62 Drill angles 4 2.1.63 - 65 Drilling - Cutting speed, feed and r.p.m , drill holding devices 6 2.1.66 Counter sinking 9 2.1.67 Reamers 16 2.1.68 - 69 Screw thread and elements 22 2.1.70 Tap wrenches, removal of broken tap, studs 32 2.1.71 Dies and die stock 36 2.1.72 - 73 Drill troubles - Causes and remedy, drill kinds 40 2.1.74 - 75 Standard marking system for Grinding wheels 46 2.1.76 Radius/Fillet gauge, feeler gauge, hole gauge 55 2.1.77 - 78 Pig Iron 60 Module 2: Fitting assembly 2.2.79 - 80 Necessity of Interchangeability in engineering field 63 2.2.81 Vernier height gauge 73 2.2.82 Wrought iron and plain carbon steels 75 2.2.83 - 85 Simple scrapers and scraping 81 2.2.86 - 88 Vernier micrometer, screw thread micrometer, graduation & reading 86 2.2.89 Dial test indicator, comparators, digital dial indicator 93 Module 3: Turning 2.3.90 Safety to be observed while working on lathes 102 2.3.91 Lathe main parts 104 2.3.92 Feeding & thread cutting mechanism 110 2.3.93 Holding the job between centre and work with catch plate and dog 113 2.3.94 Simple description of facing and roughing tool 115 2.3.95 Nomanclature of single point cutting tools and multi point cutting tools 117 2.3.96 Tool selection based on different requirements 120 2.3.97 Necessity of grinding angles 123 (vii) Copyright Free Under CC BY Licence.

[Audio] Lesson No. Title of the Lesson Page No. 2.3.98 Lathe cutting speed and feed, use of coolants, lubricants 125 2.3.99 Chucks and chucking - the independent 4 jaw chuck 130 2.3.100 Face plate 136 2.3.101 Drilling 138 2.3.102 Boring & boring tools 139 2.3.103 Tool setting 141 2.3.104 Tool post 145 2.3.105 Lathe operation - Knurling 147 2.3.106 Standard tapers 150 2.3.107 Screw thread 154 2.3.108 Principle of cutting screw thread in centre lathe 158 2.3.109 Principle of chasing screw thread 161 Module 4 : Basic Maintenance 2.4.110 Total productive maintenance 168 2.4.111 Routine maintenance 170 2.4.112 Preventive maintenance 172 2.4.113 Inspection, types of inspection and gadgets for inspection 177 2.4.114 Lubrication survey 180 2.4.115 Causes for assembly failures and remedies 183 2.4.116 Assembly techniquies 184 (viii) Copyright Free Under CC BY Licence.

[Audio] LEARNING / ASSESSABLE OUTCOME On completion of this book you shall be able to Produce components by different operations and check accuracy using appropriate measuring instrument. [ Different OperationsDrilling, reaming, tapping, dieing., Appropriate measuring instruments - Vernier, screw gauge, micrometer.] Make different fit of components for assembling as per required tolerance observing principle of interchargeability and check for functionality. [ Different fit-sliding, angular, step fit, 'T' fit, square fit and profile fit., Required tolerance; ±±±±± 0.04 mm, angular tolerace: 30 min] Produce components involving different operations on lathe observing standard procedure and check for accuracy. [ Different operations - Facing, plain turning, step turning, parting, chamfering, shoulder turn, grooving, knurling, boring, taper turning, threading (external 'V' only.] Plan & perform simple rapair, overhauling of different machines and check for functionality. [ Different machines - Drill machine, power saw, bench grinder and lathe.] (ix) Copyright Free Under CC BY Licence.

[Audio] SYLLABUS 1st Year (Volume II of II) Duration: Six Month Professional Knowledge (Trade Theory) Week No. Ref. Learning Outcome Professional Skills (Trade Practical) with Indicative hours 27 61 Mark off and drill through holes. (5 hrs.) 62 Drill on M.S. flat. (1 hrs.) 63 File radius and profile to suit gauge (13 hrs.) Drill- material, types, (Taper shank, straight shank) parts and sizes. Drill angle-cutting angle for different materials, cutting speed feed. R.P.M. for different materials. Drill holding devicesmaterial, construction and their uses. 64 Sharpening of Drills.(1 hrs.) 65 Practice use of angular measuring instrument. (5 hrs.) Produce componentsby different operations and check accuracy using appropriate measuring instruments.[Different O p e r a t i o n s - D r i l l i n g , Reaming, Taping, Dieing; Appropriate Measuring Instrument – Vernier, Screw Gauge, Micrometer] 28 -do66 Counter sink, counter bore and ream split fit (three piece fitting). (5 hrs.) 67 Drill through hole and blind holes. (2 hrs.) 68 Form internal threads with taps to standard size (through holes and blind holes).(3 hrs.) 69 Prepare studs and bolt.(15 hrs.) Counter sink, counter bore and spot facing-tools and nomenclature, Reamermaterial, types (Hand and machine reamer), kinds, parts and their uses, determining hole size (or reaming), Reaming procedure. Screw threads: terminology, parts, types and their uses. Screw pitch gauge: material parts and uses. Taps British standard (B.S.W., B.S.F., B.A. & B.S.P.) and metric / BIS (course and fine) material, parts (shank body, flute, cutting edge). 29 -do70 Form external threads with dies to standard size. (10 hrs.) 71 Prepare nuts and match with bolts.(15 hrs.) Tap wrench: material, parts, types (solid &adjustable types) and their uses removal of broken tap, studs (tap stud extractor). Dies: British standard, metric and BIS standard, material, parts, types, Method of using dies. Die stock: material, parts and uses. (x) Copyright Free Under CC BY Licence.

[Audio] -do30 72 File and make Step fit, angular fit, angle, surfaces (Bevel gauge accuracy 1 degree).(15 hrs.) Drill troubles: causes and remedy. Equality of lips, correct clearance, dead centre, length of lips. Drill kinds: Fraction, metric, letters and numbers, grinding of drill. 73 Make simple open and sliding fits. (10 hrs.) -do31 74 Enlarge hole and increase internal dia. (2 hrs.) 75 File cylindrical surfaces.(5 hrs.) 76 Make open fitting of curved profiles.(18 hrs.) Grinding wheel: Abrasive, grade structures, bond, specification, use, mounting and dressing. Selection of grinding wheels. Bench grinder parts and use. Radius/fillet gauge, feeler gauge, hole gauge, and their uses, care and maintenance. -do32 77 Correction of drill location by binding previously drilled hole.(5 hrs.) Pig Iron: types of pig Iron, properties and uses. Cast Iron: types, properties and uses. 78 Make inside square fit. (20 hrs.) 33 79 Make sliding „T. fit.(2 hrs.) Interchangeability: Necessity in Engg, field definition, BIS. Definition, types of limit, terminology of limits and fits-basic size, actual size, deviation, high and low limit, zero line, tolerance zone Different standard systems of fits and limits. British standard system, BIS system Make different fit of components for assembling as per required tolerance observing principle of interchangeability and check for f u n c t i o n a l i t y . [Different Fit – Sliding, Angular, Step fit, 'T' fit, Square fit and Profile fit; Required tolerance: ±0.04 mm, angular tolerance: 30 min.] 34 -do80 File fit- combined, open angular and sliding sides. (10 hrs.) 81 File internal angles 30minutes accuracy open, angular fit.(15 hrs.) Method of expressing tolerance as per BIS Fits: Definition, types, description of each with sketch. Vernier height gauge: material construction, parts, graduations (English & Metric) uses, care and maintenance. -do35-36 82 Make sliding fit with angles other than 90°.(25 hrs.) Wrought iron- : properties and uses. Steel: plain carbon steels, types, properties and uses. Non-ferrous metals (copper, aluminum, tin, lead, zinc) properties and uses. (xi) Copyright Free Under CC BY Licence.

[Audio] -do37 83 Scrap on flat surfaces, curved surfaces and parallel surfaces and test. (5 hrs.) 84 Make & assemble, sliding flats, plain surfaces. (15 hrs.) Simple scraper- circular, flat, half round, triangular and hook scraper and their uses. Blue matching of scraped surfaces (flat and curved bearing surfaces) 85 Check for blue math of bearing surfaces - both flat and curved surfaces by with worth method.(5hrs.) -do38 86 File and fit combined radius and angular surface (accuracy ± 0.5 mm), angular and radius fit. (18 hrs.) 87 Locate accurate holes & make accurate hole for stud fit.(2 hrs.) Vernier micrometer, material, parts, graduation, use, care and intenance. Calibration of measuring instruments. Introduction to mechanical fasteners and its uses. Screw thread micrometer: Construction, graduation and use. 88 Fasten mechanical components / subassemblies together using screws, bolts and collars using hand tools. (5 hrs.) -do39 89 Make sliding fits assembly with parallel and angular mating surface. (± 0.04 mm) (25 hrs.) Dial test indicator, construction, parts, material, graduation, Method of use, care and maintenance. Digital dial indicator. Comparatorsmeasurement of quality in the cylinder bores. 40 90 Lathe operations91 True job on four jaw chuck using knife tool.(5 hrs.) 92 Face both the ends for holding between centers. (9 hrs.) 93 Using roughing tool parallel turn ± 0.1 mm. (10 hrs.) 94 Measure the diameter using outside caliper and steel rule.(1hrs.) Safely precautions to be observed while working on a lathe, Lathe specifications, and constructional features. Lathe main parts descriptions- bed, head stock, carriage, tail stock, feeding and thread cutting mechanisms. Holding of job between centers, works with catch plate, dog, simple description of a facing and roughing tool and their applications. Produce components involving different operations on lathe observing standard procedure and check for accuracy. [Different Operations – facing, plain turning, step turning, parting, chamfering, shoulder turn, grooving, knurling, boring, taper turning, threading (external 'V' only)] 41 -do95 Holding job in three jaw chuck.(2 hrs.) 96 Perform the facing, plain turn, step turn, parting, deburr, chamfercorner, round the ends, and use form tools. (11 hrs.) Lathe cutting tools- Nomenclature ofsingle point & multipoint cutting tools, Tool selection based on different requirements and necessity of correct grinding, solid and tipped, throw away (xii) Copyright Free Under CC BY Licence.

[Audio] type tools, cutting speed and feed and comparison for H.S.S., carbide tools. Use of coolants and lubricants. 97 Shoulder turn: square, filleted, beveled undercut shoulder, turningfilleted under cut, square beveled. (11 hrs.) 98 Sharpening of -Single point Tools. (1 hrs.) 42 -do99 Cut grooves- square, round,V. groove. (10 hrs.) 100 Make a mandrel-turn diameter to sizes. (5 hrs.) 101 Knurl the job.(1 hrs.) Chucks and chucking the independent four-jaw chuck. Reversible features of jaws, the back plate, Method of clearing the thread of the chuck-mounting and dismounting, chucks, chucking true, face plate, drilling - method of holding drills in the tail stock, Boring tools and enlargement of holes. 102 Bore holes –spot face, pilot drill, enlarge hole using boring tools. (9 hrs.) 43 -do103 Make a bush step bore-cut recess, turn hole diameter to sizes.(5 hrs.) 104 Turn taper (internal and external). (10 hrs.) 105 Turn taper pins. (5 hrs.) 106 Turn standard tapers to suit with gauge.(5 hrs.) General turning operations- parallel or straight, turning. Stepped turning, grooving, and shape of tools for the above operations. Appropriate method of holding the tool on tool post or tool rest, Knurling: - tools description, grade, uses, speed and feed, coolant for knurling, speed, feed calculation. Taper – definition, use and method of expressing tapers. Standard taperstaper, calculations morse taper. 44 -do107 Practice threading using taps, dies on lathe by hand. (2 hrs.) 108 Make external „V. thread.(8 hrs.) 109 Prepare a nut and match with the bolt.(15 hrs.) Screw thread definition – uses and application. Square, worm, buttress, acme ( non standard-screw threads), Principle of cutting screw thread in centre lathe –principle of chasing the screw thread – use of centre gauge,setting tool for cutting internal and external threads, use of screw pitch gauge for checking the screw thread. 45-46 110 Simple repair work: Simple assembly of machine parts from blue prints. (15 hrs.) 111 Rectify possible assembly faults during assembly.(19 hrs.) 112 Perform the routine maintenance with check list (10 hrs.) Plan & perform simple repair, overhauling of different machines and check for f u n c t i o n a l i t y. [Different Machines – Drill Machine, Power Saw, Bench Grinder and Lathe] 113 Monitor machine as per routine checklist (3 hrs.) 114 Read pressure gauge, temperature gauge, oil level (1 hrs.) Maintenance -Total productive maintenance Autonomous maintenance -Routine maintenance -Maintenance schedule -Retrieval of data from machine manuals Preventive maintenanceobjective and function of Preventive maintenance, section inspection. Visual and detailed, lubrication survey, system of symbol and colour coding. Revision, simple estimation of materials, use of handbooks and reference table. Possible causes for assembly failures and remedies. 115 Set pressure in pneumatic system (2 hrs.) (xiii) Copyright Free Under CC BY Licence.

[Audio] -do47 116 Assemble simple fitting using dowel pins and tap screw assembly using torque wrench. (25 hrs.) Assembling techniques such as aligning, bending, fixing, mechanical jointing, threaded jointing, sealing, and torquing.Dowel pins: material, construction, types, accuracy and uses. In-plant training / Project work 48-49 1 Pipe Fixture 2 Adjustable Clamp 3 Hermaphrodite/ Inside Caliper 4 Chuck Key 50-51 Revision 52 Examination (xiv) Copyright Free Under CC BY Licence.

[Audio] Production & Manufacturing Related Theory for Exercise 2.1.61 Fitter - Drilling Drills Objectives: At the end of this lesson you shall be able to state drilling state the necessity of drilling name the types of drills used identify the parts of a twist drill. The flutes provide a correct cutting angle which provides an escape path for the chips. It carries the coolant to the cutting edge during drilling. (Fig 3) Drilling: Drilling is the production of cylindrical holes of definite diameters in workpieces by using a multi-point cutting tool called a 'drill'. It is the first operation done internally for any further operation. Types of drills and their specific uses Flat drill (Fig 1) : The earliest form of drill was the flat drill which is easy to operate,besides being inexpensive to produce. But it is difficult to hold during operation,and the chip removal is poor. Its operating efficiency is very low. Twist drill : Almost all drilling operation is done using a twist drill. It is called a twist drill as it has two or more spiral or helical flutes formed along its length. The two basic types of twist drills are, parallel shank and taper shank. Parallel shank twist drills are available below 13mm size (Fig 2). The portions left between the flutes are called 'lands'. The size of a drill is detemined and governed by the diameter over the lands. The point angle is the cutting angle, and for general purpose work, it is 118°. The clearance serves the purpose of clearing the back of the lip from fouling with the work. It is mostly 8°. Deep hole drills Deep hole drilling is done by using a type of drill known as 'D' bit (Fig 4) Drills are made of high speed steel. Parts of a twist drill : Drills are made out of high speed steel. The spiral flutes are machined at an angle of 27 1/ 2° to its axis. 1 Copyright Free Under CC BY Licence.

[Audio] FIN216114 Drills are manufactured with varying helix angles for drilling different materials. General purpose drills have a standard helix angle of 27 1/2°. They are used on mild steel and cast iron. (Fig 5a) FIN216115 A slow helix drill is used on materials like brass, gun metal, phosphor-bronze and plastics. (Fig 5b) A quick helix drill should never be used on brass as it will 'dig in' and the workpiece may be thrown from the machine table. A quick helix drill is used for copper, aluminium and other soft metals (Fig 5c) Drill (Parts and functions) Objectives: At the end of this lesson you shall be able to state the functions of drills identify the parts of a drill state the functions of each part of a drill. Drilling is a process of making holes on workpieces.The tool used is a drill. For drilling, the drill is rotated with a downward pressure causing the tool to penetrate into the material. (Fig 1) Parts of a Drill (Fig 2) The various parts of a drill can be identified from figure 2. Point The cone shaped end which does the cutting is called the point. It consists of a dead centre, lips or cutting edges, and a heel. Body Shank The portion between the point and the shank is called the body of a drill. This is the driving end of the drill which is fitted on to the machine. Shanks are of two types. The parts of the body are flute, land/margin, body clearance and web. Taper shank, used for larger diameter drills, and straight shank, used for smaller diameter drills. (Fig 3) Flutes (Fig 3) Tang Flutes are the spiral grooves which run to the length of the drill. The flutes help This is a part of the taper shank drill which fits into the slot of the drilling machine spindle. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.61 2 Copyright Free Under CC BY Licence.

[Audio] To form the cutting edges The diameter of the drill is measured across the land/ margin. To curl the chips and allow these to come out The coolant to flow to the cutting edge. Body clearance (Fig 3) Land/Margin (Fig 3) Body clearance is the part of the body which is reduced in diameter to cut down the friction between the drill and the hole being drilled. Web (Fig 4) Web is the metal column which separates the flutes. It gradually increases in thickness towards the shank. The land/margin is the narrow strip which extends to the entire length of the flutes. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.61 3 Copyright Free Under CC BY Licence.

[Audio] Production & Manufacturing Related Theory for Exercise: 2.1.62 Fitter - Drilling Drill angles Objectives: At the end of this lesson you shall be able to identify the various angles of a twist drill state the functions of each angle list the types of helix for drills as per ISI distinguish the features of different types of drills designate drills as per ISI recommendations. Like all cutting tools the drills are provided with certain angles for efficiency in drilling. Twist drills are made with different helix angles. The helix angle determines the rake angle at the cutting edge of the twist drill. Drill angles They are different angles for different purposes. They are listed below. The helix angles vary according to the material being drilled. According to indian standards, three types of drills are used for drilling various materials. Type N - For normal low carbon steel. Point angle, helix angle, rake angle, clearance angle and chisel edge angle. Type H - For hard and tenaceous materials. Point angle/ cutting angle (Fig 1) Types S - For soft and tough materials. The type of drill used for general purpose drilling work is type N. Rake angle (Fig 5) The point angle of a general purpose (standard) drill is 118°. This is the angle between the cutting edges (lips). The angle varies according to the hardness of the material to be drilled. (Fig 1) Helix angle (Figs 2,3 and 4) Rake angle is the angle of flute (helix angle). Clearance angle (Fig 6) 4 Copyright Free Under CC BY Licence.

[Audio] Designation of drills Twist drills are designated by the The clearance angle is meant to prevent the friction of the tool behind the cutting edge. This will help in the penetration of the cutting edges into the material. If the clearance angle is too much, the cutting edges will be weak, and if it is too small, the drill will not cut. Diameter Tool type Chisel edge angle/web angle (Fig 7) Material Example A twist drill of 9.50 mm dia. of tool type 'H' for right hand cutting and made from HSS is designated as: Twist drill 9.50 - H - IS5101 - HS where H = tool type IS5101 = IS Number HS = tool material This is the angle between the chisel edge and the cutting lip. 9.5 = diameter of the drill. If the tool type is not indicated in the designation, it should be taken as type 'N' tool. DRILLS FOR DIFFERENT MATERIALS Recommended drills Material to be Point Helix angle Material to be Point Helix angle drilled angle d=3.2-5 5-10 10 drilled angle d=3.5-5 5Steel and cast steel Copper (up to 30 mm up to 70 kgf/mm2 drill diameter) strength Al-alloys,forming Gray cast iron curly chips Malleable cast iron Celluloid Brass German silver, nickel. Brass, CuZn 40 Austenitic steels Magnesium alloys Steel and cast steel Moulded plastics 70...120 Kgf/mm2 (with thickness s>d) Moulded plastics, with thickness s<d Laminated plastics, Stainless steel; hard rubber (ebonite) Copper (drill diameter.

[Audio] Production & Manufacturing Related Theory for Exercise 2.1.63 - 65 Fitter - Drilling Drilling - Cutting speed, feed and r.p.m , drill holding devices Objectives: At the end of this lesson you shall be able to define cutting speed state the factors for determining the cutting speed differentiate between cutting speed and rpm determine r.p.m/spindle speed select r.p.m for drill sizes from the tables. Cutting speed calculation For a drill to give a satisfactory performance, it must operate at the correct cutting speed and feed. Cutting speed (V) Cutting speed is the speed at which the cutting edge passes over the material while cutting, and is expressed in metres per minute. Cutting speed is also sometimes stated as surface speed or peripheral speed. n r.p.m. v Cutting speed in m/min. d diameter of the drill in mm. The selection of the recommended cutting speed for drilling depends on the materials to be drilled,and the tool material. π = 3.14 Examples Tool manufacturers usually provide a table of cutting speeds required for different materials. Calculate the r.p.m for a high speed steel drill ∅ 24 to cut mild steel. The recommended cutting speeds for different materials are given in the Table 1. Based on the cutting speed recommended, the r.p.m, at which a drill has to be driven is determined. The cutting speed for mild steel is taken as 30 m/min from the table. TABLE 1 Recommendad cutting speeds Materials being drilled (HSS Tool) Aluminium 70 - 100 Brass 35 - 50 It is always preferable to set the spindle speed to the nearest available lower range. Bronze(phosphor) 20 - 35 Cast iron (grey) 25 - 40 Copper 35 - 45 The r.p.m. will differ according to the diameter of the drills. The cutting speed being the same, larger diameter drills will have lesser r.p.m and smaller diameter drills will have higher r.p.m. Steel (medium carbon/mild steel) 20 - 30 Steel (alloy, high tensile) 5 - 8 The recommended cutting speeds are achieved only by actual experiment. Thermosetting plastic (low speed due to abrasive properties) 20 - 30 Feed in drilling Objectives: At the end of this lesson you shall be able to state what is meant by feed state the factors that contribute to an efficient feed rate. Feed is the distance (X) a drill advances into the work in one complete rotation. (Fig 1) Feed is expressed in hundredths of a millimeter. 6 Copyright Free Under CC BY Licence.

[Audio] The table gives the feed rate which is based on the average feed values suggested by the different manufacturers of drills. (Table 1) TABLE 1 Drill diameter Rate of feed (mm) H.S.S (mm/rev) 1.0 - 2.5 0.040 - 0.060 2.6 - 4.5 0.050 - 0.100 4.6 - 6.0 0. 075 - 0.150 6.1 - 9.0 0.100 - 0.200 Example - 0.040mm/ rev 9.1 - 12.0 0.150 - 0.250 12.1 - 15.0 0.200 - 0.300 The rate of feed is dependant up on a number of factors. 15.1 - 18.0 0.230 - 0.330 The finish required 18.1 - 21.0 0.260 - 0.360 Type of drill (drill material) 21.1 - 25.0 0.280 - 0.380 Material to be drilled Too coarse a feed may result in damage to the cutting edges or breakage of the drill. Factors like rigidity of the machine, holding of the workpiece and the drill, will also have to be considered while determining the feed rate. If these are not to the required standard, the feed rate will have to be decreased. Too slow a rate of feed will not bring improvement in surface finish but may cause excessive wear of the tool point, and lead to chattering of the drill. It is not possible to suggest a particular feed rate taking all the factors into account. For optimum results in the feed rate while drilling, it is necessary to ensure the drill cutting edges are sharp. Use the correct type of cutting fluid. Drill-holding devices Objectives: At the end of this lesson you shall be able to name the different types of drill-holding devices state the features of drill chucks state the functions of drill sleeves state the function of drift. For drilling holes on materials, the drills are to be held accurately and rigidly on the machines. The common drill-holding devices are drill chucks, sleeves and sockets. Drill chucks: Straight shank drills are held in drill chucks. (Fig 1A) For fixing and removing drills, the chucks are provided either with a pinion and key or a knurled ring. The drill chucks are held on the machine spindle by means of an arbor (Fig 1B) fitted on the drill chuck. Taper sleeves and sockets (Fig 2): Taper shank drills have a Morse taper. Sleeves and sockets are made with the same taper so that the taper shank of the drill, when engaged, will give a good wedging action. Due to this reason Morse tapers are called self-holding tapers. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.63 - 65 7 Copyright Free Under CC.

[Audio] In order to make up the difference in sizes between the shanks of the drills and the bore of machine spindles, sleeves of different sizes are used. When the drill taper shank is bigger than the machine spindle, taper sockets are used. (Fig 2) While fixing the drill in a socket or sleeve, the tang portion should align in the slot. This will facilitate the removal of the drill or sleeve from the machine spindle. Use a drift to remove drills and sockets from the machine spindle. (Fig 3) While removing the drill from the sockets/sleeves don't allow it to fall on the table or jobs. The drills are provided with five different sizes of Morse tapers, and are numbered from MT 1 to MT 5. Drill chucks are made from special alloy steel Drill sleeves are made from case hardened steel Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.63 - 65 8 Copyright Free Under CC BY Licence.

[Audio] Production & Manufacturing Related Theory for Exercise 2.1.66 Fitter - Drilling Counter sinking Objectives: At the end of this lesson you shall be able to state countersinking list the purposes of countersinking state the angles of countersinking for the different applications name the different types of countersinks distinguish between Type A and Type B counter sink holes. What is countersinking? The commonly used countersinks have multiple cutting edges and are available in taper shank and straight shank. (Fig 2) Countersinking is an operation of bevelling the end of a drilled hole. The tool used is called a countersink. Countersinking is carried out for the following purposes: To provide a recess for the head of a countersink screw, so that it is flush with the surface after fixing (Fig 1) To deburr a hole after drilling For accommodating countersink rivet heads For countersinking small diameter holes special countersinks with two or one flute are available. This will reduce the vibration while cutting. To chamfer the ends of holes for thread cutting and other machining processes. Countersinks with Pilot (Fig 3) Angles for countersinking Countersinks are available in different angles for different uses. For precision countersinking, needed for machine tool assembling and after machining process, countersinks with pilots are used. 75° countersink riveting They are particularly useful for heavy duty work. 80° countersink self tapping screws 90° countersink head screws and deburring The pilot is provided at the end for guiding the countersink concentric to the hole. 120° chamfering ends of holes to be threaded or other machining processes. Countersinks with pilots are available with interchangeable and solid pilots. Countersink hole sizes Countersinks Countersinks of different types are available. The countersink holes according to Indian Standard IS 3406 (Part 1) 1986 are of four types: Type A, Type B, Type C and Type E. 9 Copyright Free Under CC BY Licence.

[Audio] Type A is suitable for slotted countersink head screws, cross recessed and slotted raised countersink head screws. These screws are available in two grades i.e. medium and fine. The dimensions of various features of the Type 'A' countersink holes, and the method of designation are given in Table 1. Type 'B' countersink holes are suitable for countersink head screws with hexagon socket. The dimensions of the various features and the method of designation are given in Table II. Type 'C' countersink holes are suitable for slotted raised countersink (oval) head tapping screws and for slotted countersink (flat) head tapping screws. The dimension of the various features and the method of designation are given in Table III. Type 'E' countersinks are used for slotted countersink bolts used for steel structures. The dimensions of the various features and the method of designation are given in Table IV. TABLE I Dimensions and designation of countersink - Type A according to IS 3406 (Part 1) 1986 Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.66 10 Copyright Free Under CC BY Licence.

[Audio] TABLE I For Nominal Size 1 1.2 (1.4) 1.6 (1.8) 2 2.5 3 3.5 4 (4.5) Medium d1 H13 1.2 1.4 1.6 1.8 2.1 2.4 2.9 3.4 3.9 4.5 5 Series d2 H13 2.4 2.8 3.3 3.7 4.1 4.6 5.7 6.5 7.6 8.6 9.5 (m) t1 ³ 0.6 0.7 0.8 0.9 1 1.1 1.4 1.6 1.9 2.1 2.3 Fine d1 H12 1.1 1.3 1.5 1.7 2 2.2 2.7 3.2 3.7 4.3 4.8 Series d3 H12 2 2.5 2.8 3.3 3.8 4.3 5 6 7 8 9 (f) t1 ³ 0.7 0.8 0.9 1 1.2 1.2 1.5 1.7 2 2.2 2.4 t2 + 0.1 0.2 0.15 0.15 0.2 0.2 0.15 0.35 0.25 0.3 0.3 0.3 0 For Nominal Size 5 6 8 10 12 (14) 16 (18) 20 Medium d1 H13 5.5 6.6 9 11 13.5 15.5 17.5 20 22 Series d2 H13 10.4 12.4 16.4 20.4 23.9 26.9 31.9 36.4 40.4 (m) t1 ³ 2.5 2.9 3.7 4.7 5.2 5.7 7.2 8.2 9.2 Fine d1 H12 5.3 6.4 8.4 10.5 13 15 17 19 21 Series d3 H12 10 11.5 15 19 23 26 30 34 37 (f) t1 ³ 2.6 3 4 5 5.7 6.2 7.7 8.7 9.7 t2 + 0.1 0.2 0.45 0.7 0.7 0.7 0.7 1.2 1.2 1.7 0 Note 1 : Size shown in brackets are of second preference. Note 2 : Clearance hole d1 according to medium and fine series of IS : 1821 ' Dimensions for clearance holes for bolts and screws (second revision)' Designation : A countersink Type A with clearance hole of fine (f) series and having nominal size 10 shall be designated as – Countersink A f 10 - IS : 3406. TABLE II Dimensions and designation of countersink - Type B according to IS 3406 (Part 1) 1986 Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.66 11 Copyright Free Under CC BY Licence.

[Audio] For Nominal Size 3 4 5 6 8 10 12 (14) 16 (18) 20 22 24 Fine d1 H12 3.2 4.3 5.3 6.4 8.4 10.5 13 15 17 19 21 23 25 Series d2 H12 6.3 8.3 10.4 12.4 16.5 20.5 25 28 31 34 37 48.2 52 (f) t1 ³ 1.7 2.4 2.9 3.3 4.4 5.5 6.5 7 7.5 8 8.5 13.1 14 t2 + 0.1 0.2 0.3 0.4 0.5 1 Note 1: Sizes shown in brackets are of second preference. Note 2: Clearance hole d1 according to medium and fine series of IS : 1821- 1982. Designation : A countersink Type B with clearance hole of fine (f) series and having nominal size 10 shall be designated as – Countersink B f 10 - IS : 3406. TABLE III Dimensions and designation of countersink - Type C according to IS 3406 (Part 1) 1986 For Screw Size No. (0) (1) 2 (3) 4 (5) 6 (7) 8 10 (12) 14 (16) d1 H12 1.6 2 2.4 2.8 3.1 3.5 3.7 4.2 4.5 5.1 5.8 6.7 8.4 d2 H12 3.1 3.8 4.6 5.2 5.9 6.6 7.2 8.1 8.7 10.1 11.4 13.2 16.6 t1 ³ 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.6 3 3.4 3.9 4.9 Note : Sizes given in brackets are of second preference. Designation : A countersink Type C for screw size 2 shall be designated as – Countersink C 2 - IS : 3406. TABLE IV Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.66 12 Copyright Free Under CC BY Licence.

[Audio] Dimension and designation of countersink - Type E according to IS 3406 (Part 1) 1986 For Nominal No. 10 12 16 20 22 24 d1 H12 10.5 13 17 21 23 25 d2 H12 19 24 31 34 37 40 t1 ³ 5.5 7 9 11.5 12 13 α ± 1° 75° 60° Note: Clearance hole d1 according to fine series of IS : 1821 - 1982 Designation : A countersink Type E for nominal size 10 shall be designated as – Countersink E 10 - IS : 3406. Methods of representing countersink holes in drawings Countersink hole sizes are identified by code designation or using dimension. Use of code designation Use of dimension The dimension of the countersink can be expressed by the diameter of the countersink and the depth of the countersink. Counterboring and spot facing Objectives: At the end of this lesson you shall be able to differentiate counterboring and spot facing state the types of counterbores and their uses determine the correct counterbore sizes for different holes. Counterbore (Tool) Counterboring The tool used for counterboring is called a counterbore. (Fig 2) Counterbores will have two or more cutting edges. Counterboring is an operation of enlarging a hole to a given depth, to house heads of socket heads or cap screws with the help of a counterbore tool. (Fig 1) Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.66 13 Copyright Free Under CC BY Licence.

[Audio] Spot facing Spot facing is a machining operation for producing a flat seat for bolt head, washer or nut at the opening of a drilled hole. The tool is called a spot facer or a spot facing tool. Spot facing is similar to counterboring, except that it is shallower. Tools that are used for counterboring can be used for spot facing as well. (Fig 4) Spot facing is also done by fly cutters by end-cutting action. The cutter blade is inserted in the slot of the holder, which can be mounted on to the spindle. (Fig 5) Counterbore sizes and specification At the cutting end, a pilot is provided to guide the tool concentric to the previously drilled hole. The pilot also helps to avoid chattering while counterboring. (Fig 3) Counterbore sizes are standardised for each diameter of screws as per BIS. There are two main types of counterbores. Type H and Type K. The type H counterbores are used for assemblies with slotted cheese head, slotted pan head and cross recessed pan head screws. The type K counterbores are used in assemblies with hexagonal socket head capscrews. For fitting different types of washers the counterbore standards are different in Type H and Type K. The clearance hole d1 are of two different grades i.e. medium (m) and fine (f) and are finished to H13 and H12 dimensions. Counterbores are available with solid pilots or with interchangeable pilots. The interchangeable pilot provides flexibility of counterboring on different diameters of holes. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.66 14 Copyright Free Under CC BY Licence.

[Audio] Dimensions for H and K Type counter bores The table given below is a portion from IS 3406 (Part 2) 1986. This gives dimensions for Type H and Type K counterbores. While representing counterbores in drawings, counterbores can be indicated either by code designation or using the dimensions. Counterbore and Clearance Hole Sizes for Different Sizes of Screws Table - 1 For Nominal size 1 1.2 1.4 1.6 1.8 2 2.5 3 (3.5) 4 5 6 8 10 12 (14) 16 18 20 22 24 27 30 33 36 Medium (m) 1.2 1.4 1.6 1.8 2.1 2.4 2.9 3.4 3.9 4.5 5.5 6.6 9 11 13.5 15.5 17.5 20 22 24 26 30 33 36 39 H13 d1 fine (f) 1.1 1.3 1.5 1.7 2 2.2 2.7 3.2 3.7 4.3 5.3 6.4 8.4 10.5 13 15 17 19 21 23 25 - H12 d2 H13 2.2 2.5 2.8 3.3 3.8 4.3 5 6 6.5 8 10 11 15 18 20 24 26 30 33 36 40 43 48 53 57 d3 15.5 17.5 19.5 22 24 26 28 33 36 39 42 Type H 0.8 0.9 1 1.2 1.5 1.6 2 2.4 2.9 3.2 4 4.7 6 7 8 9 10.5 11.5 12.5 13.5 14.5 - t1 Type K 1.6 1.8 2.3 2.9 3.4 4.6 5.7 6.8 9 11 13 15 17.5 19.5 21.5 23.5 25.5 28.5 32 35 38 +0.1 +0.2 +0.4 +0.6 Tolerances 0 0 0 0 Note : Sizes given in brackets are of second preference. For details refer IS : 3406 (Part2) 1986. Using code designation (Fig 7) Using dimensions (Fig 8) Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.66 15 Copyright Free Under CC BY Licence.

[Audio] Production & Manufacturing Related Theory for Exercise 2.1.67 Fitter - Drilling Reamers Objectives: At the end of this lesson you shall be able to state the use of reamers state the advantages of reaming distinguish between hand and machine reaming name the elements of a reamer and state their functions. What is a reamer? Reaming by using hand reamers is done manually for which great skill is needed. A reamer is a multipoint cutting tool used for enlarging by finishing previously drilled holes to accurate sizes. (Fig 1) Machine reamers are fitted on spindles of machine tools and rotated for reaming. Machine reamers are provided with morse taper shanks for holding on machine spindles. Hand reamers have straight shanks with 'square' at the end, for holding with tap wrenches. (Figs 2 (a) and (b) Parts of a hand reamer The parts of a hand reamer are listed hereunder. Refer to Fig 3. Advantages of 'reaming' Reaming produces High quality surface finish Dimensional accuracy to close limits. Also small holes which cannot be finished by other processes can be finished. Classification of reamers Reamers are classified as hand reamers and machine reamers. (Figs 2a and 2b) Axis The longitudinal centre line of the reamer. Body The portion of the reamer extending from the entering end of the reamer to the commencement of the shank. Recess The portion of the body which is reduced in diameter below the cutting edges, pilot or guide diameters. 16 Copyright Free Under CC BY Licence.

[Audio] Cutting edge Shank The portion of the reamer which is held and driven. It can be parallel or taper. The edge formed by the intersection of the face and the circular land or the surface left by the provision of primary clearance. (Fig 4) Circular land Face The cylindrically ground surface adjacent to the cutting edge on the leading edge of the land. Bevel lead The portion of the flute surface adjacent to the cutting edge on which the chip impinges as it is cut from the work. (Fig 4) Rake angles The bevel lead cutting portion at the entering end of the reamer cutting its way into the hole. It is not provided with a circular land. The angles in a diametral plane formed by the face and a radial line from the cutting edge. (Fig 5) Taper lead The tapered cutting portion at the entering end to facilitate cutting and finishing of the hole. It is not provided with a circular land. Bevel lead angle The angle formed by the cutting edges of the bevel lead and the reamer axis. Taper lead angle The angle formed by the cutting edges of the taper and the reamer axis. Terms relating to cutting geometry Flutes Clearance angle The grooves in the body of the reamer to provide cutting edges, to permit the removal of chips, and to allow the cutting fluid to reach the cutting edges. (Fig 4) The angles formed by the primary or secondary clearances and the tangent to the periphery of the reamer at the cutting edge. They are called primary clearance angle and secondary clearance angle respectively. (Fig 6) Helix angle Heel The angle between the edge and the reamer axis. (Fig 7) The edge formed by the intersection of the surface left by the provision of a secondary clearance and the flute. (Fig 4) Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.67 17 Copyright Free Under CC BY Licence.

[Audio] Hand reamers Objectives: At the end of this lesson you shall be able to state the general features of hand reamers identify the types of hand reamers distinguish between the uses of straight fluted and helical fluted reamers name the materials from which reamers are made and specify reamers. General features of hand reamers (Fig 1) Parallel hand reamer with parallel shank (Fig 4a) Hand reamers are used to ream holes manually using tap wrenches. A reamer which has virtually parallel cutting edges with taper and bevel lead. The body of the reamer is integral with a shank. The shank has the nominal diameter of the cutting edges. One end of the shank is square shaped for tuning it with a tap wrench. Parallel reamers are available with straight and helical flutes. This is the commonly used hand reamer for reaming holes with parallel sides. These reamers have a long taper lead.(Fig 2) This allows to start the reamer straight and in alignment with the hole being reamed. Reamers commonly used in workshop produce H7 holes. Hand reamer with pilot (Fig 4b) Most hand reamers are for right hand cutting. Helical fluted hand reamers have left hand helix. The left hand helix will produce smooth cutting action and finish. Most reamers, machine or hand, have uneven spacing of teeth. This feature of reamers helps to reduce chattering while reaming. (Fig 3) Types, features and functions For this type of reamer, a portion of the body is cylindrically ground to form a pilot at the entering end. The pilot keeps the reamer concentric with the hole being reamed. Hand reamers with different features are available for meeting different reaming conditions. The commonly used types are listed here under: Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.67 18 Copyright Free Under CC BY Licence.

[Audio] Socket reamer with parallel shank (Figs 5a and 5b) This reamer has tapered cutting edges to suit metric morse tapers. The shank is integral with the body, and is square shaped for driving. The flutes are either straight or helical. The socket reamer is used for reaming internal morse tapered holes. Taper pin hand reamer (Fig 5c) Material of hand reamers When the reamers are made as a one-piece construction, high speed steel is used. When they are made as two-piece construction then the cutting portion is made of high speed steel while the shank portion is made of carbon steel. They are butt-welded together before manufacturing. Specifications of a reamer To specify a reamer the following data is to be given. Type Flute This reamer has tapered cutting edges for reaming taper holes to suit taper pins. A taper pin reamer is made with a taper of 1 in 50. These reamers are available with straight or helical flutes. Shank end Use of straight and helical fluted reamers (Fig 6) Size Example : Hand reamer, Straight flute, Parallel shank of Ø 20 mm. Straight fluted reamers are useful for general reaming work. Helical fluted reamers are particularly suitable for reaming holes with keyway grooves or special lines cut into them. The helical flutes will bridge the gap and reduce binding and chattering. Drill size for reaming Objective: At the end of this lesson you shall be able to determine the hole size for reaming. Drill size = Reamed size – (Undersize + Oversize) For reaming with a hand or a machine reamer, the hole drilled should be smaller than the reamer size. Finished size Finished size is the diameter of the reamer. The drilled hole should have sufficient metal for finishing with the reamer. Excessive metal will impose a strain on the cutting edge of the reamer and damage it. Undersize Calculating drill size for reamer Undersize is the recommended reduction in size for different ranges of drill diameter. (Table 1) A method generally practised in workshop is by applying the following formula. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.67 19 Copyright Free Under CC BY Licence.

[Audio] Undersizes for reaming Note: If the reamed hole is undersize, the cause is that the reamer is worn out. TABLE 1 Always inspect the condition of the reamer before commencing reaming. Diameter of Undersize of ready reamed rough bored hole (mm) hole (mm) For obtaining good surface finish under 5 0.1.....0.2 5......20 0.2.....0.3 Use a coolant while reaming. Remove metal chips from the reamer frequently. Advance the reamer slowly into the work. 21....50 0.3.....0.5 over 50 0.5.....1 Defects in reaming - Causes and Remedies Oversize Reamed hole undersize It is generally considered that a twist drill will make a hole larger than its diameter. The oversize for calculation purposes is taken as 0.05 mm - for all diameters of drills. - If a worn out reamer is used, it may result in the reamed hole bearing undersize. Do not use such reamers. For light metals the undersize will be chosen 50% larger. - Always inspect the condition of the reamer before using. Example Surface finish rough The causes may be any one of the following or a combinations thereof. A hole is to be reamed on mild steel with a 10 mm reamer. What will be the diameter of the drill for drilling the hole before reaming? Incorrect application Drill size = Reamed size – (Undersize + Oversize) Swarf accumulated in reamer flutes (Finished size) = 10 mm Inadequate flow of coolant Feed rate too fast Undersize as per table = 0.2 mm While reaming apply a steady and slow feed-rate. Oversize = 0.05 mm Ensure a continuous supply of the coolant. Drill size = 10 mm -- 0.25 mm Do not turn the reamer in the reverse direction. = 9.75 mm Determining the drill size for reaming Determine the drill hole sizes for the following reamers: Use the formaula, i 15 mm drill diameter = reamed hole size. (undersize + oversize) ii 4 mm iii 40 mm Refer to the table for the recommended undersizes in Related Theory on DRILL SIZES FOR REAMING. iv 19 mm Answer i _________________________________________ ii _________________________________________ iii _________________________________________ iv _________________________________________ Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.67 20 Copyright Free Under CC BY Licence.

[Audio] Reaming Objectives : At the end of this lesson you shall be able to state the procedure for hand reaming and machine reaming. Reaming Reaming is the operation of finishing and sizing a hole which has been previously drilled, bored, casteed holes. The tool used is called a reamer, which has multiple cutting edges. Manually it is held in a tap wrench and reamed. Machine reamer are used in drilling machine using sleeves (or) socket. Normally the speed for reaming will be 1/3rd speed of drilling. Hand Reaming Drill holes for reaming as per the sizes determined. Do not turn in reverse direction it will scratch the reamed hole. (Fig 4) Place the work on parallels while setting on the machine vice. (Fig 1) Ream the hole through, ensure that the taper lead length of the reamer comes out well and clear from the bottom of the work. Do not allow the end of the reamer to strike on the vice. Chamfer the hole ends slightly. This removes burrs and will also help to align the reamer vertically. (Fig 2) Fix the work in the bench vice. Use vice clamps to protect the finished surfaces. Ensure that the job is horizontal. (Fig 2) Remove the reamer with an upward pull until the reamer is clear of the hole. (Fig 5) Remove the burrs from the bottom of the reamed hole. Clean the hole. Check the accuracy with the cylindrical pins supplied. Fix the tap wrench on the square end and place the reamer vertically in the hole. Check the alignment with a try square. Make corrections, If necessary. Turn the tap wrench in a clockwise direction applying a slight downward pressure at the same time. (Fig 3) Apply pressure evenly at both ends of the tap wrench. Apply cutting force Turn the tap wrench steadily and slowly, maintaining the downward pressure. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.67 21 Copyright Free Under CC BY Licence.

[Audio] Production & Manufacturing Related Theory for Exercise 2.1.68 - 69 Fitter - Drilling Screw thread and elements Objectives: At the end of this lesson you shall be able to state the terminology of screw threads state the types of screw threads. Screw thread terminology Parts of screw thread (Fig 1) Minor Diameter Crest For external threads, the minor diameter is the smallest diameter after cutting the full thread. In the case of internal threads, it is the diameter of the hole drilled for forming the thread which is the minor diameter. The top surface joining the two sides of a thread. Pitch Diameter (effective diameter) Root The diameter of the thread at which the thread thickness is equal to one half of the pitch. The bottom surface joining the two sides of adjacent threads. Pitch Flank The surface joining the crest and the root. It is the distance from a point on one thread to a correspond ing point on the adjacent thread measured parallel to the axis. Thread angle Lead The included angle between the flanks of adjacent threads. Depth Lead is the distance of a threaded component moves along the matching component during one complete revolution. For a single start thread the lead is equal to the pitch. The perpendicular distance between the roots and crest of the thread. Helix Angle Major Diameter The angle of inclination of the thread to the imaginary perpendicular line. Hand In the case of external threads it is the diameter of the blank on which the threads are cut and in the case of internal threads it is the largest diameter after the threads are cut that are known as the major diameter. (Fig 2) The direction in which the thread is turned to advance. A right hand thread is turned clockwise to advance, while a left hand thread is turned anticlockwise.( Fig 3) This is the diameter by which the sizes of screws are stated. 22 Copyright Free Under CC BY Licence.

[Audio] Screw threads - types of V threads and their uses Objectives: At the end of this lesson you shall be able to state the different standards of V threads indicate the angle and the relation between the pitch with the other elements of the thread state the uses of the different standards of V threads. BSF thread The different standards of V threads are: BSW thread: British Standard Whitworth thread BSF thread: British Standard fine thread BSP thread: British Standard pipe thread B.A thread: British Association thread This thread is similar to BSW thread except the number of TPI for a particular diameter. The number of threads per inch is more than that for the BSW thread for a particular diameter. For Example, 1" BSW has 8 TPI and 1 "BSF has 10 TPI. The table indicates the standard number of TPI for different dia. of BSF threads. It is used in automobile industries. I.S.O Metric thread: International Standard Organisation metric thread ANS: American National or sellers' thread BSP thread BIS Metric thread: Bureau of Indian Standard metric thread. BSW thread (Fig 1) This thread is recommended for pipe and pipe fittings. The table shows the pitch for different diameters. It is also similar to BSW thread. The thread is cut externally with a small taper for the threaded length. This avoids the leakage in the assembly and provides for further adjustment when slackness is felt. BA thread (Fig 2) It has an included angle of 55° and the depth of the thread is 0.6403 x P. The crest and root are rounded off to a definite radius . The figure shows the relationship between the pitch and the other elements of the thread. BSW thread is represented in a drawing by giving the major diameter. For example : 1/2" BSW, 1/4" BSW. The table indicates the standard number of TPI for different diameters. BSW thread is used for general purpose fastening threads. This thread has an included angle of 47 1/2°. Depth and other elements are as shown in the figure. It is used in small screws of electrical appliances, watch screws, screws of scientific apparatus. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 23 Copyright Free Under CC BY Licence.

[Audio] Unified thread (Fig 3) For the fine series, the letter 'M' is followed by the major diameter and pitch. Ex : M14 x 1.5 M24 x 2 For both the metric and inch series, ISO has developed this thread. Its angle is 60°. The crest and root are flat and the other dimensions are as shown in the figure. This thread is used for general fastening purposes. American National Thread (Fig 4) These threads are also called as seller's threads. It was more commonly used prior to the introduction of the ISO unified thread. This thread of metric standard is represented in a drawing by the letter 'M' followed by the major diameter for the coarse series. Ex : M14, M12 etc. Screw pitch gauge Objectives: At the end of this lesson you shall be able to state the purpose of a screw pitch gauge state the features of a screw pitch gauge. Purpose A screw pitch gauge is used to determine the pitch of a thread. The thread profile on each blade is cut for about 25 mm to 30 mm. The pitch of the blade is stamped on each blade. The standard and range of the pitches are marked on the case. (Fig 1) It is also used to compare the profile of threads. Constructional features Pitch gauges are available with a number of blades assembled as a set. Each blade is meant for checking a particular standard thread pitch. The blades are made of thin spring steel sheets, and are hardened. Some screw pitch gauge sets will have blades provided for checking British Standard threads (BSW, BSF etc.) at one end and the metric standard at the other end. Taps Objectives: At the end of this lesson you shall be able to state the uses of hand taps state the features of hand taps distinguish between the different taps in a set. Use of hand taps: Hand taps are used for internal threading of components. Features (Fig 1): They are made from high speed steel. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 24 Copyright Free Under CC BY Licence.

[Audio] The threads are cut on the periphery and are accurately finished. To form the cutting edges, flutes are cut across the thread. The end of the shank of the tap is made of square shape for the purpose of holding and turning the taps. The end of the taps are chamfered (taper lead) for assisting, aligning and starting of the thread. The size of the taps, the thread standard, the pitch of the thread, the dia. of the tapping hole are usually marked on the shank. Marking on the shank are also made to indicate the type of tap i.e. first, second and plug. The taper tap is to start the thread. It is possible to form full threads by the taper tap in through holes which are not deep. Types of taps in a set : Hand taps for a particular thread are available as a set consisting of three pieces. (Fig 2) These are: The bottoming tap (plug) is used to finish the threads of a blind hole to the correct depth. – First tap or taper tap – Second tap or intermediate tap For identifying the type of taps quickly - the taps are either numbered 1,2 and 3 or rings are marked on the shank. – Plug or bottoming tap. The taper tap has one ring, the intermediate tap has two and the bottoming tap has three rings. (Fig 2) These taps are identical in all features except in the tap lead. 25 Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 Copyright Free Under CC BY Licence.

[Audio] Table for tap drill size B.S.F. (55°) B.S.W. (55°) Tap size Threads per Tap drill (inch) inch size (mm) Tap size Threads per Tap drill (inch) inch size (mm) 3/16 32 3.97mm 3/16 24 3.7mm 7/32 28 4.6mm 7/32 24 4.5mm 1/4 26 5.3mm 1/4 20 5.1mm 5/16 22 6.75mm 5/16 18 6.5mm 3/8 20 8.2mm 3/8 16 7.94mm 7/16 18 9.7mm 7/16 14 9.3mm 1/2 16 11.11mm 1/2 12 10.5mm 9/16 16 12.7mm 9/16 12 12.1mm 5/8 14 14mm 5/8 11 13.5mm 11/16 14 15.5mm 11/16 11 15mm 3/4 12 16.75mm 3/4 10 16.257mm 7/8 11 19.84mm 7/8 9 19.25mm 1" 10 22.75mm 1" 8 22mm NPT National pipe thread Tap size Threads per Tap drill Tap size Threads per Tap drill size (inch) inch size inch (inch) inch inch 1/8 27 11/32 1 11 1/2 1 5/32 1/4 18 7/16 1 1/4 11 1/4 1 1/2 3/8 18 19/32 1 1/2 11 1/2 1 23/32 1/2 14 23/32 2 11 1/2 2 23/16 3/4 14 15/16 2 1/2 8 2 5/8 Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 26 Copyright Free Under CC BY Licence.

[Audio] Tap drill sizes ISO Inch (Unified) thread NC National coarse NF National Fine Tap size Threads per Tap drill Tap size Threads per Tap drill size (inch) inch size inch (inch) inch inch 1/4 20 13/64 1/4 28 7/32 5/16 18 17/64 5/16 24 17/64 3/8 16 5/16 3/8 24 21/64 7/16 14 3/8 7/16 20 25/64 1/2 13 27/64 1/2 20 29/64 9/16 12 31/64 9/16 18 33/64 5/8 11 17/32 5/8 18 37/64 3/4 10 21/32 3/4 16 11/16 7/8 9 49/64 7/8 14 13/16 1" 8 7/8 1" 14 15/16 1 1/8 7 63/64 1 1/8 12 1 3/6 1 1/4 7 17/64 1 1/4 12 1 11/6 1 3/8 6 17/32 1 3/8 12 1 19/64 1 1/2 6 1 11/32 1 1/2 12 1 27/64 1 3/4 5 1 9/16 2" 4 1/2 1 25/32 27 Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 Copyright Free Under CC BY Licence.

[Audio] Machine taps Objectives: At the end of this lesson you shall be able to state the characteristics of machine taps name the different types of machine taps state the features and uses of different types of machine taps. Machine taps: Machine taps of different types are available. The two important features of machine taps are Flute-less taps are used for tapping through holes on materials which are not thicker than the diameter of the holes. Flutless spiral point taps are best suited for tapping soft materials or thin metal sections. – Ability to withstand the torque needed for threading holes – Provision for eliminating chip jamming. Helical fluted taps/spiral fluted taps: These taps have spiral flutes which bring out the chips from the hole being tapped. (Fig 4) Types of machine taps Gun tap (Spiral pointed tap) (Fig 1) These are useful for tapping holes with slots. The helical land of the tap will bridge the interruption of the surface being threaded. The helical flutes of the tap provide a shear cutting action, and are mostly used to tap holes in ductile materials like aluminium, brass, copper etc. These taps are especially useful for machine tapping of through holes. In the case of blind hole tapping, there should be sufficient space below to accommodate the chips. While tapping, the chips are forced out ahead of the tap. (Fig 2) Spiral fluted taps are also available with fast spiral. (Fig 5) These taps are best suited for tapping deep holes as these can clear the chips faster from the hole. (Fig 6) This prevents the clogging of the chips and thus reduces the chances of tap breakage. These taps are stronger since the flutes are shallow. The flutes of these taps do not convey chips. Flute-less spiral pointed tap (Stub flute taps) (Fig 3): Thread forming taps (Fluteless taps) These taps form threads in the hole by displacing the material and not by cutting action. (Fig 7) These taps have short angular flutes ground on the chamfered end, and the rest of the body is left solid. These taps are stronger than gun taps. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 28 Copyright Free Under CC BY Licence.

[Audio] These taps have projecting lobes which actually help in forming the thread. (Fig 8) Since there are no chips in the process, it is very valuable in places where chip removal poses problems. These taps are excellent for tapping copper, brass, aluminium, lead etc. The thread finish is also comparatively better than in the fluted taps. General informative points on taps Objectives: At the end of this lesson you shall be able to differentiate between hand tap and machine tap identify the parts of a machine tap state the constructional features of a machine tap. Accordingly three types of taps are available. Type normal (Fig 3b ) with a rake angle of approximately 12°. Type soft (Fig 3c) with a rake angle of approximately 20°. Type hard (Fig 3a) with a rake angle of approximately 3°. Unlike tapping with the three piece set of hand taps, the machine tap cuts the entire threaded profile in one operation. The machine tap is normally made of tool steel and consists of the shank (2) and the cutting section (1) as shown in (Fig 1). The cutting section itself is subdivided into two areas. The start (3), which serves for cutting, and the guiding section (4) for the feeding motion and smoothing of the newly cut thread. (Fig 1) The number of flutes (5), may be even or odd. With an even number of flutes, measuring of the diameter (7) is easier. (Figs 2a and 2b) The normal type of rake angle taps can be used in most cases. The start must be ground symmetrical. Before using the tap, it is necessary to check that the cutting edges are not chipped, and all the edges are sharp. The 'hard' type tap is used for tapping brittle materials like cast iron. In case a 'normal' type tap is used on cast iron, the tap cutting edges get blunt soon and the tap cannot be used again on ductile materials like mild steel. The fine cast iron splinters wear the external diameter of the cutting edges of the tap causing them to tend to become blunt, and when the same tap is used on steel which is more flexible it is elastically pressed away (8) at the cutting point. Behind the cutting edge the material returns to the machined diameter. The depth of the groove also causes jamming of the guiding section of the tap. (Fig 4) Straight and spiral groove machine taps are available. The diameter of the shank and the shape of its end vary between the various standards. The shank diameter may be smaller, equal to or larger than the thread diameter. The shank ends are available in straight design, with square ends as shown in (6) or with driving shoulders. Chip removal (flow) takes place at the start of the tap. The rake angle must be adapted to the material to be machined. Hard and brittle materials require a small rake angle and soft materials need a larger rake angle. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 29 Copyright Free Under CC BY Licence.

[Audio] Pipe Threads and Pipe Taps Objectives: At the end of this lesson you shall be able to state parallel and taper pipes threads determine the wall thickness and threads per inch (TPI) of BSP threads state the method of sealing pipe joints determine blank sizes for threading as per B.S 21 - 1973 and I.S. 2643 - 1964. Pipe threads The standard pipe fittings are threaded to British Standard pipe (BSP). The internal pipe threads have parallel threads whereas the external pipes have tapered threads as shown in Fig 1. The pipe joint shown in Fig 4 consists of the following: 1 Parallel female thread 2 Tapered male thread 3 Hemp packing The hamp packing isused to ensure that any small space between two metal threads (male and female threads) is sealed to prevent any leakage. B.S.P. threads Glavinized iron pipes are available in sizes ranging from 1/2" to 6" in several different wall thickness. The table shows outside diameters and threads per inch from 1/2" to 4". (Fig 2) Table BSP - Pipe sizes Threads Outside diameter/ or DIN 2999 inch mm of the pipe (A) (inside) (B) 1/2" 14 20.955 mm 3/4" 14 26.441 1" 11 33.249 11/4" 11 41.910 The next two threads have fully formed bottoms but that tops. (B) 11/2" 11 47.803 The last four threads have flat tops and bottoms. (C) 2" 11 59.614 Sealing pipe joint 2 1/2" 8 75.184 3" 8 87.884 Fig 3 shows that the pipe has several fully formed threads at the end. (A) 4" 8 113.030 Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 30 Copyright Free Under CC BY Licence.

[Audio] Pipe taps Internal pipe threads are usually cut with standard taper pipe taps. (Fig 5) In gauging internal pipe threads, the pipe plug thread gauge should be screwed tight by hand into the pipe until the notch on the gauge is flush with the face. When the thread is chamfered the notch should be flushed with the bottom of the chamfer. (Fig 6) Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.68 - 69 31 Copyright Free Under CC BY Licence.

[Audio] Production & Manufacturing Related Theory for Exercise 2.1.70 Fitter - Drilling Tap wrenches, removal of broken tap, studs Objectives : At the end of this lesson you shall be able to name the different types of tap wrenches state the uses of the different types of wrenches. Tap wrenches These are small, adjustable chucks with two jaws and a handle to turn the wrench. Tap wrenches are used to align and drive the hand taps correctly into the hole to be threaded. This tap wrench is useful to work in restricted places, and is turned with one hand only. Most suitable for smaller sizes of taps. Tap wrenches are of different types, such as double-ended adjustable wrench, T- handle tap wrench, solid type tap wrench etc. Solid type tap wrench (Fig 3) Double - ended adjustable tap wrench or bar type tap wrench (Fig 1) These wrenches are not adjustable. They can take only certain sizes of taps. This eliminates the use of wrong length of the tap wrenches, and thus prevents damage to the taps. This is the most commonly used type of tap wrench. It is available in various sizes- 175, 250,350mm long. These tap wrenches are more suitable for large diameter taps, and can be used in open places where there is no obstruction to turn the tap. Material It is important to select the correct size of wrench. T- handle tap wrench (Fig 2) Made from a single piece of solid Cast iron (or) steel. Cast iron and steel are used because of strong, durable and unlikely to deform under pressure. Removing broken taps Objectives: At the end of this lesson you shall be able to name the different methods of removing broken taps state the methods of removing broken taps. Use of tap extractor (Fig 1) A tap broken above the surface of the workpiece can be removed using using gripping tools like pliers. This is a very delicate tool and need very careful handling. Taps broken below the surface pose a problem for removing. Any one of the several methods given below can be used. 32 Copyright Free Under CC BY Licence.

[Audio] Use of arc welding This is a suitable method when a small tap is broken at the bottom of materials like copper, aluminium etc. In this method the electrode is brought in contact with the broken tap and stuck so that it is attached with the broken tap. The tap may be removed by rotating the electrode. Use of nitric acid This extractor has fingers which can be inserted on the flutes of the broken tap. The sliding collar is then brought to the surface of the work and the extractor turned anticlockwise to take out the broken tap. A light blow on the broken tap with a punch will help to relieve the tap if it is jammed inside the hole. Use of punch (Fig 2) In this method nitric acid is diluted in a proportion of about one part acid to five parts of water is injected inside. The action of the acid loosens the tap and then it is removed with an extractor or with a nose plier. The workpiece should be thoroughly cleaned for preventing further action of the acid. While diluting acid mix acid to water. In this method the point of the punch is placed in the flute of the broken tap in an inclination and struck with a hammer the positioning of the punch should be such that the broken tap is rotated anticlockwise when struck. Use of spark erosion For salvaging certain precision components damaged due to breakage of taps, spark erosion can be used. In this process, the metal (broken tap ) is removed by means of repetitive spark discharges. The electrical discharge occurs between an electrode and the electro - conductive workpiece (tap) and the minute particles are eroded both from the electrode and the workpiece. In many cases it may not be necessary to remove the broken tap completely. ( After a small portion has been eroded, a screw- driver or punch can be used to remove the remaining portion of the tap.) The shape of the electrode also need not be round. It can be for assisting the tools for rotaing the broken tap. Annealing and drilling the tap This is a method adopted when other method fail. In the process the broken tap is heated by flame or by other methods for annealing. A hole is then drilled on the annealed tap. The remaining piece can be removed either by using a drift or using an EZY - OUT (extractor). This method is not suitable for workpieces with low melting temperatures such as aluminium, copper etc. (Fig 3) Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.70 33 Copyright Free Under CC BY Licence.

[Audio] Removing broken stud Objectives: At the end of this lesson you shall be able to state the reasons for breakage of stud state different methods for removing broken stud. The stud is used in place of a bolt ,when there is insufficient space to accomodate the bolt head or to avoid use of an unnecessarily long bolt. Studs are generally used to fix up cover plates or to connect cylinder covers to engine cylinders. Reasons for breakage of stud/bolt. Excessive torque is applied while screwing the stud into the hole. Corrosive attack on the thread. Matching threads are not of proper formation. Threads are seized. Methods of removing broken studs Prick punch method If the stud is broken very near to the surface, drive it in an anticlockwise direction, using a prick punch and hammer to remove it. (Fig 1) EZY - out method (Fig 4) Ezy - out or a stud extactor is a hand tool, somewhat similar to the form of a taper reamer but has left hand spiral. It is available in a set of 5 pieces. The recommended drill size is punched on each ezy - out . After drilling the hole recommended ezy - out is set on it and turned in an anti - clockwise direction by a tap wrench. As it is rotated it penetrates into the hole increasing its grip and in the process the broken stud gets unscrewed. (Fig 4) Filing square form When the stud is broken a lilttle above the surface form a square on the projecting portion to suit a standard spanner. Then turn it anticlockwise using a spanner to remove it. (Fig 2) Using square taper punch Broken stud can also be removed by drilling a blind hole (hole diameter equals to half of stud diameter) and driving a square taper punch into the hole as shown in Fig 3. Turn the punch using a suitable spanner in an anti - clock- wise direction to unscrew the stud. Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.70 34 Copyright Free Under CC BY Licence.

[Audio] Making drill hole If all other method fail, drill a hole equal to the size of the stud size or a little over and tap the hole with an oversize tap.Now a special over size stud as shown in Fig 6 is to be made and fitted in position. Correctly find out the centre of the broken stud and drill hole nearly equal to the core diameter of the stud down the centre so that the threads only remain. Remove the thread portion by the point of a scriber in the form of broken chips. Re - tap the drill the hole to clear the threads. (Fig 5) Production & Manufacturing: Fitter (NSQF Level - 5) RT for Ex No. 2.1.70 35 Copyright Free Under CC BY Licence.

[Audio] Production & Manufacturing Related Theory for Exercise: 2.1.71 Fitter - Drilling Dies and die stock Objectives: At the end of this lesson you shall be able to identify the different types of dies state the features of each type of die state the use of each type of die name the type of diestock for each type of die. Uses of dies Threading dies are used to cut external threads on cylindrical workpieces. (Fig 1) Half die (Fig 4) Types of dies The folowing are the different types of dies. Circular split die (Button die) FIN217113 FIN217114 Half die Half dies are stronger in construction. Adjustable screw plate die Adjustments can be made easily to increase or decrease the depth of cut. Circular split die/button die (Fig 2) These dies are available in matching pairs and should be used together. By adjusting the screw of the diestock, the die pieces can be brought closer together or can be moved apart. They need a special die holder. FIN217111 FIN217112 Adjustable screw plate die (Fig 5) This has a slot cut to permit slight variation in size. This is another type of a two piece die similar to the half die. Dies are made of high speed steel This provides greater adjustment than the split die. The two die halves are held securely in a collar by means of a threaded plate (guide plate) which also acts as a guide while threading. When held in the diestock, variation in the size can be made by using the adjusting screws. This permits increasing or decreasing of the depth of cut. When the side screws are tightened the die will close slightly. (Fig 3) For adjusting the depth of the cut, the centre screw is advanced and locked in the groove. T his type or die stock is called button pattern stock When the guide plate is tightened after placing the die pieces in the collar, the die pieces are correctly located and rigidly held. 36 Copyright Free Under CC BY Licence.