Metalworkers' Hints and Tips for Home Machinists E-Book

• Herausgeber: Fox Chapel Publishing
• Kategorie: Lebensstil
• Sprache: Englisch
• Veröffentlichungsjahr: 2021

Seitenzahl: 233

Beschreibung

From the leading magazine for metalworkers since 1898, Model Engineer, comes this curated collection of practical advice and useful tips anyone in the industry needs to know! Jam-packed with information that's as relevant today as it was during its original publication, spanning from the 1890s to the 1960s, Metalworkers' Hint and Tips include sections on lathes and lathe work, benchwork, machine tools and accessories, electrical queries, and other miscellaneous topics. These best-of tips are the most fascinating, helpful, and time- and money-saving tips metalworkers will ever need! Author Vic Smeed was the editor of Model Maker magazine for almost 20 years and is the author of 16 modeling, metalworking, and other workshop books.

Leseprobe

Metalworkers’ Hints and Tips

Edited by Vic Smeed

Copyright © 2021 by Fox Chapel Publishing Company, Inc., Mount Joy, PA.

Copyright © Special Interest Model Books Ltd 2003

First published by Nexus Special Interest Ltd. 1997

Second edition published by Special Interest Model Books Ltd. 2003 and edited by Vic Smeed

First published in North America in 2021 by Fox Chapel Publishing, 903 Square Street, Mount Joy, PA 17552.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior permission of the copyright holder.

Print ISBN: 978-1-4971-0175-3eISBN: 978-1-63741-042-4

To learn more about the other great books from Fox Chapel Publishing, or to find a retailer near you, call toll-free 800-457-9112 or visit us at www.FoxChapelPublishing.com.

We are always looking for talented authors. To submit an idea, please send a brief inquiry to [email protected].

AMERICAN INCH PRODUCTS

Size

T.P.I.

Major Dia.

UNC

UNF

inch

0

80

0.060

1

64

72

0.073

2

56

64

0.086

3

48

56

0.099

4

40

48

0.112

5

40

44

0.125

6

32

40

0.138

8

32

36

0.164

10

24

32

0.190

12

24

28

0.216

¼

20

28

0.250

5/16

18

24

0.313

⅜

16

24

0.375

7/16

14

20

0.438

½

13

20

0.500

⅝

11

18

0.625

¾

10

16

0.750

⅞

9

14

0.875

1

8

14/12

1.000

METRIC PRODUCTS

Size

Thread Pitch

Major Dia.

T.P.I.

mm

mm

inch

inch

M1.6

0.35

1.60

0.063

73

M2.0

0.40

2.00

0.079

64

M2.5

0.45

2.50

0.098

56

M3

0.50

3.00

0.118

51

M4

0.70

4.00

0.157

36

M5

0.80

5.00

0.197

32

M6

1.00

6.00

0.236

25

M8

1.25

8.00

0.315

20

M10

1.50

10.00

0.394

17

M12

1.75

12.00

0.472

14 ½

M14

2.00

14.00

0.551

12 ½

M16

2.00

16.00

0.630

12 ½

M20

2.50

20.00

0.787

10

M24

3.00

24.00

0.945

8 ½

BRITISH INCH PRODUCTS

Size

T.P.I.

Major Dia.

BSW

BSF/BA

inch

8BA

59.1

0.087

6BA

47.9

0.110

⅛

40

0.125

5BA

43.0

0.126

4BA

38.5

0.142

3BA

34.8

0.161

2BA

31.4

0.185

3/16

24

32.0

0.187

1BA

28.2

0.209

0BA

25.4

0.236

¼

20

26.0

0.250

5/16

18

22.0

0.313

⅜

16

20.0

0.375

7/16

14

18.0

0.438

½

12

16.0

0.500

⅝

11

14.0

0.625

¾

10

12.0

0.750

⅞

9

11.0

0.875

1

8

10.0

1.000

Contents

Introduction

SECTION 1 Lathes and Lathework

Removable Nose for a Mandrel

Center with Tool-setting Peg

Divider for a Portass

Tapers

Cutting Metric Threads

Forming and Finishing a Screwthread

Cutting Square Threads

Packing

Lathe Carrier

Lathe Center Gauge and Scriber

Sensitive Drilling Attachment

Boring and Facing Tools

Collet Chucks

Second Operation Set-ups

Boring Recesses

Lathe Toolposts

A High Speed Turning Hint

A Simple Lead Screw Chip Guard

Clasp Nut Engagement Stop

Simple Tool

Improvised Steady

Screwcutting B.A. Threads

Setting Lathe to Turn Parallel

How to Plane Small Gears

A Center-spacing Punching Tool

Boring Bar Attachment

Turning and Boring Phosphor Bronze

Query — Form Tool of Complicated Shape

Curing the “Incurable Chuck”

Tightening Adjusting Screws on Cross Slides of Small Lathes

Cutting Multi-thread Screws

Query — Knurling Troubles

Twisted Rods

A Chuck for Small Screws

Overcoming the Deficiencies of Inaccurate Machine Tools

Making Screws

SECTION 2 Benchwork

Hints on Filing

File Cleaning

The Art of Drilling Holes

Winding Small Springs

Prevent of Noise

Small Bends, Sets and Joggles

Adjustable Wire-bending Tool

Winding Helical Springs

Working Pipes and Tubes

Mandrel for Cutting Rings from Thin Tubing

Adjustable Jig for Drilling Round Stock

Handling Small Nuts

Fixing Small Rivets

A Simple Marking Gauge

Toolmaker’s Cramps

Gear Wheel Repairs

Chisels from Needle Files

Vee Supports

Vise to Set Small Studs

Cultivating Caliper Accuracy

Wood Lathe Bow Nuts

Sharpening Small Twist Drills

Drilling Hexagonal Holes

Query — Holes in Thin Sheet Metal

Square-ending a Drilled Hole

Straightedge and Surface Plate

Query — Scraping Planed Plates

Non-slip Tap Wrench

To Save Broken Taps

Simple Tap Wrench

Tap Grinding and Binding

Lubricants for Tapping

Some Causes of Taps Breaking

Cross-drilling Shafts in Vise

Hacksaw and Scratch Brush Hints

Uses for Powdered Graphite

Drilling Laminations

A Handy Drilling Jig for Joint Pins, Round Bars, etc.

Removing Broken Taps and Drills from Castings

A Simple Hole-chamfering Tool

Holding Hacksaw Blade for Depth Slotting

SECTION 3 Machine Tools and Accessories

Spigot Cutter for Shouldering Rods

Tip from Canada

Small Bench Grinder

A Tip in Grinding Copper

Safety Washer for Grinding-wheel Spindle Nut

Freehand Grinding

Oiling Lathes and Machine Tools

Jointing Band Saw Blades

Query — Drilling Machine Chatter

Gripping Slips for the Machine Vise

Simple Belt Tensioning Device

Belt Dressings

SECTION 4 Electrical

Electrical Heating Elements

Query — Motor Trouble

Query — Running Cable to Workshop Motor

Query — Pressure-operated Switch

Query — Dynamo Not Working After Repair

Query — Wrong Direction

Query — Small Solenoids

Query — Horsepower of Motor

SECTION 5 Miscellaneous

Safety in the Workshop

Chemical Coloring of Metals

What Metal Is It?

Making Oilcans

Make Your Own Modeling Clay

Query — Sand for Molding

Hand Cream

P.T.F.E.

Metric System

A Simple Forge

A Simple Furnace

Casting Aluminum Alloys

Melting Aluminum

Measurement of High Temperatures

Low-temperature Solders

Query — Glass Grinding

Nameplates

Query — Marking Steel Tools

Extracting a Tight Pinion

Query — Etching Brass

A Simple Method of Making Clock Hands

Making and Using Case-Hardening Compound

A Home Made Lubricant

Planishing Sheet Metal

Introduction

When the far-sighted Percival Marshall founded The Model Engineer and Amateur Electrician in January 1898 it was, to paraphrase his words, in recognition of the army of workers whose tastes lay in the direction of mechanics and electricity having no journal devoted to the subjects from the amateur’s point of view. At that time most people were more familiar with horses than machines and the internal combustion engine and electricity, which would in time supplant wind, water and steam as major power sources, were relatively recent innovations. There were engineers in industry who could pursue their interest in spare time, using knowledge acquired at work, but there were far more potential enthusiasts who had no mechanical background and needed education and guidance, both provided in abundance by the magazine at just twopence a week!

As electricity grew to become taken for granted and its widespread use created an ever-expanding market for mass-produced equipment, the necessity or incentive for amateur construction diminished and the ‘Amateur Electrician’ part of the title was discontinued. The ‘Model’ aspect of the title reflects the fact that an engineering model requires much the same machinery and techniques as full-size prototypes, but on a scale and with work sizes more suited to the home workshop. To make something which functions gives point to those who enjoy working with metal as a hobby; their materials and methods are also shared with professionals who earn their living from the output of small machine shops.

Over the years an enormous amount of useful information has been published, from lengthy series of articles by eminent engineers to brief tips from average enthusiasts. Some of this material has subsequently appeared in book form, but most lies undiscovered by those who do not easily have access to early issues. This book is, effectively, a random dip into the middle fifty years of the magazine, offering an assortment of ideas relating to general metalwork, with the emphasis on lathe usage and benchwork and an occasional glimpse of practices now not so frequently encountered. It is hoped that at least some of the items will be of use and interests to readers of any degree of experience.

SECTION 1

Lathes and Lathework

Removable Nose for a Mandrel

H.S. Wheeler (November 1964)

A useful addition to a Myford ML7 lathe is a removable nose for the outer end of the mandrel. I found it quite simple to make.

It consists of a nosepiece which is a replica of the standard mandrel nose, and an extending neck which is stepped.

The ¾ in. dia. step passes through the hole in the gear guard and forms a stop at the end of the mandrel. The end of the smaller 19/32 in. dia. step is sawcut and coned out, and a mating cone is made.

A 5/16 in. dia. clearing hole is drilled right through the attachment and in this is passed a long stud, screwed 5/16 in. Whitworth at each end.

To assemble the device on the lathe we need only push it right home in the mandrel and then tighten the external nut, which draws the cone into the taper and expands the end of the stepped part. The clamping is quite rigid.

If the standard faceplate is now screwed on the nose part, it will be very useful for turning the mandrel by hand, as in small screwing or tapping operations. By securing the appropriate disk to the faceplate you can also use the device for sanding or finishing, by running the lathe at top speed. The mandrel should then be run in reverse, to prevent the possibility that the faceplate will unscrew.

It will save you the removal of a good deal of stock if you make the nosepiece and stepped tailpiece separately and then screw and pin the tailpiece into the nosepiece. You can remove the device instantly by slackening off the external nut and giving the spindle a light tap to clear the tapered cone, when the whole can be pulled out.

Center with Tool-setting Peg

(January 1924)

The appended view represents an idea for tool-setting down to quite small diameters by the use of a peg inserted in a cross-hole in a special back-center. The latter should be cut away as shown so that the tool may pass along when the peg is set only to a small amount of projection.

Divider for a Portass

A.G. Allnut (April 1964)

Readers with a Portass or similar lathe may be interested in my divider, if they have a 60t bull wheel. The conical shape detent is, perhaps, not perfect but it works well enough.

Tapers

‘Geometer’ (January 1957)

The desirable true running of a pulley or flywheel taper-fitted on a shaft is generally best ensured by finishing faces and outside diameter with the component mounted on a mandrel running between centers in the lathe. All important surfaces are thus finished at one setting and the wheel is both parallel and concentric—a condition difficult to achieve by chucking and re-chucking no matter how carefully this may be done.

The preliminary roughing out is advisedly done in a chuck (which can be a four-jaw independent type with the jaws reversed if necessary, since heavier cuts can be taken in a chuck than on a mandrel) leaving about 1/64 in. surplus for finishing. In this way, scale or any hard spots in the casting can be successfully dealt with in the rough machining, using a slow rotational speed and taking cuts deep enough to be everywhere well below the surface.

Diagrams A and B illustrate typical chuck set-ups for rough machining a small flywheel, the material removed at each being shown by the shaded areas. At each set-up the wheel is pushed back to the jaws for facial alignment, and the jaws are regulated for peripheral or general spinning truth.

Although it is not vital to do so, it is generally best to machine the taper bore on the first set-up, and also to turn along the outside diameter as far as possible. On the second set-up it is then practicable to fit a taper mandrel in the bore and employ its end for checking and truing— if it should happen that it is difficult to apply the pointer of a surface gauge to a portion of the outside diameter.

Moreover, should a small error result from the setting, cleaning cuts can easily be taken on the mandrel set-up C since the particular faces will be toward the tailstock.

Taper uniformity

When the shaft is available on which the wheel is to fit, it can be tried in the taper as this is machined (or reamed) in order to locate the wheel endwise correctly— in which respect, should the taper bore be made slightly too large a reducing cut can always be taken over the face.

Alternatively, the bore can be sized from a reamer or mandrel, as at D, which may be necessary if the component is a replacement, or one is requiring to stan-dardize tapers for wheels to be fitted on different shafts. In the case of a mandrel, a shoulder can be left in machining or a sleeve can be fitted for a distance X to obtain when the taper is at correct size; in the case of a reamer, a sleeve is essential when the distance can be measured with a rule, or a small gauge made just to push into the space.

A common type of gauge for this method of sizing tapers is as E, where the taper portion ends in a step on one side X1. On the tool being pushed tightly into the bore to be tested, the step should go just below the surface while the full diameter just stands proud—showing the bore to be within its particular tolerance.

Should the gauge enter too far a light correcting cut can always be taken across the face—assuming there remains sufficient material on other faces to machine them into relationship—which is as good a reason as any for finishing the taper early in the proceedings.

The principle also applies to a shaft F where a ring gauge (corresponding to the component) is used. This may have a step X2 to locate the position where the taper finishes at the full diameter, or at the opposite end on the small diameter, though a better way is to take the distance Y from the face to a shoulder or the end of the shaft.

If a keyway is required in a wheel its cutting should be the final operation. From square drill rod a tool is made as G, turning the shank, filing the surplus to tool shape, then hardening and tempering. Planing cuts are taken from the saddle with the chuck secured against rotation, as at H, by a holding strip from backplate to headstock.

Cutting Metric Threads

The use of a 127-toothed wheel for metric screwcutting on an English lathe By Geo. Gentry (July 1955)

This article relates to a problem which is constantly recurring in both amateur and professional workshops, and it is proposed to deal with it in some detail to satisfy the requirements of querists who have asked for advice on how to produce metric threads on lathes with fractional-inch pitch lead screws. In the particular instances, the pitch of the lead screw is not specified, but it will be assumed that it is 8 t.p.i., as this is the pitch most commonly employed on English lathes of the sizes employed by model engineers. Neither is it known what change wheels may be available, but if the basic principles of the calculations are grasped, they can be adapted to different lead screws or change wheels by the use of elementary arithmetic.

Ratio of wheel numbers

If the pitch of a screw to be cut is given, the ratio of gearing required is expressed as the ratio of the pitch to be cut (on the mandrel end) to the pitch of the lead-screw (on its appropriate end). If, however, the reciprocal of the pitch be given (i.e. number of threads per inch), the reciprocal of the lead screw pitch is put on the mandrel, and the screw to be cut on the leadscrew. In the first case, as an example, if it is desired to cut a pitch of 1 mm. with a leadscrew of 2 ½ mm., the ratio of gears will be ½ ½ or 1 to 2 ½ mandrel to screw.

In the second case, if it is desired to cut 12 t.p.i. with a lead screw of 8 t.p.i., the ratio of gears will be 8/12 or 8 to 12 mandrel to screw.

Applying the second case, to explain the use of the 127 wheel, it is necessary to know that there are 25.4 mm. in 1 in., or a 1 mm. pitch screw may be expressed as 25.4 t.p.i. This is not exactly correct but has only an error of the order of two millionths of an inch in an inch which is negligible entirely.

If then we require to cut 25.4 t.p.i. with a leadscrew of 8 t.p.i., applying the second case, the ratio of gears will be 8/25.4 or 8 to 25.4 mandrel to screw. Thus:

the smallest factor which can be used to bring 25.4 to whole numbers being 5. Thus a simple train (i.e. not a compound train) made with a 40 wheel on mandrel end and 127 wheel on the 8 t.p.i. lead-screw end will cut 25.4 t.p.i. or 1 mm. pitch (Fig. 1). Forty is the driver and 127 the driven or follower of the train.

Fig. 1

Compound trains

To make clear the principle of compounding, which will be necessary in some cases where the drivers given are not available, the interested reader must understand the idea of speeding down or up in proportion to the fraction or multiplier of 1 mm. required to be cut. If, for instance, ½ mm. is required and no 20 wheel is available, the compounding wheels must have the ratio 2 to 1 down, say 48 and 24, thus retaining the original 40 driver, put it 40 driving into 48 on intermediate stud and 24 keyed to 48 on same (and running with it) driving the 127 on screw (Fig. 2).

If there should be trouble in getting the wheels to come together, the 24 and 40 drivers may be changed about, giving 24 on mandrel driving 48 on stud, and 40 on stud (keyed to 48) driving 127 on screw. If, however, 24 and 48 are either or both not available:

56 and 28; 60 and 30; 64 and 32 or any 2 to 1 wheels available may be used in the same way. Applying the principle where 0.6 mm. is required and no 24 is available, the compounding wheels must have the ratio 1 to 0.6 down or 10 to 6, say wheels 50 to 30 giving 40 driving 50 on stud and 30 keyed to 50 driving 127 on screw.

Fig. 2

Fig. 3

It is obviously impossible to prepare a correct compound table in the absence of knowledge of wheels available, but readers are advised to master the principle, and having got a correct working setting to note down the wheels used and ultimately complete their own table for reference.

There is one other instance. Say it is necessary to cut 1 ½ mm. pitch and there is no 60 available. Keeping the 40 on mandrel, speed up 1 to 1 ½ using say 20 to 30. That is 40 on mandrel, driving 20 on stud and 30 keyed to 20 driving 127 on screw.

It may be that the simple train driver is too large, even though wheels may be available; as, for instance, the use of 100 into 127, and so make useless any intermediate idle wheel or wheels. In such a case, gear down 2 to 1 by using 50 as a driver and then counter-gear up by compounding 1 to 2 with any pair. Say 20 and 40. Thus 50 on mandrel driving 20 on stud and 40 on stud (keyed to 20) driving 127 on screw will cut 2 ½ mm.

In compounding, where it is necessary to use idle wheels in a corresponding simple train to preserve the right direction of rotation, the compounding wheels serve the purpose of one idle wheel.

General requirements

The novice at setting up screwcutting trains must realize that in arranging a compound train, double-width intermediate studs are necessary, and a double-width nose on lead screw. Idle wheels may have any number of teeth. If the lead screw has a right-hand thread, the mandrel and lead screw must revolve in the same direction to cut a right-hand thread. Unless a cluster gear or other means of reversing the gear train are provided, therefore, one idler gear between mandrel and lead screw must be used; for lefthand threads, two idlers are necessary.

Fig. 4

Fig. 5

Difficulty in setting up a gear train may arise when wheels which do not mesh with each other overlap owing to their large diameter. This may occur when using, say, a 100 wheel on the mandrel and a 127 on the lead screw. It may be overcome by using an idler of double width, or two wheels of the same size keyed together, as in Fig. 4; to reverse the direction, a second idler is added, as in Fig. 5. These conditions apply to all screwcutting trains, quite apart from those used for cutting metric threads.

Metric thread table for an 8 t.p.i. lead screw (All Simple trains)

Forming and Finishing a Screwthread

E.T. Westbury (May 1963)

When V-threads of relatively coarse pitch are cut, the load on the tool point becomes very heavy, as the breadth of the cutting edge in action increases rapidly with the depth. Top rake, which in normal circumstances can be used to reduce loading in machining steel and other tough metals, has a limited value in screwcutting. Experienced turners sometimes ease the load on the tool by shifting it sideways slightly between cuts, using the topslide feed, and centralizing it only for the final cuts. This is effective if skillfully carried out, but it can hardly be recommended as a general practice, especially for the beginner, because of the risk of disastrous error.

A well-known alternative method, which is much more certain in its results, is to swivel the topslide to the flank angle of the thread, which in the Whitworth form is 27 ½ deg. from a right angle, or in other words 62 ½ deg. from the lathe axis. When the tool is fed in at this angle, it cuts on the leading flank alone, and the load on the extreme point is greatly reduced. The tool may with advantage be given side rake for dealing with steel—a downward slope from the leading flank. Using the topslide for quick withdrawal of the tool at the end of the cut is not very convenient. The usual practice is to employ the cross-slide and return it to the same point each time, applying the cutting feed only on the topslide.

Some lathes, including the Myford ML7, do not provide for sufficient swiveling of the topslide. With the type of ball handle favored (not necessarily the best, but the most popular) it is rather difficult to find room for manipulating both the cross and top feeds at this angle in lathes of limited center height. Several devices have been described in ME for increasing the swiveling range of the ML7; they usually involve the raising of the cross-slide by a packing plate, and thus restrict the size of the tool which can be used in the normal toolpost, but there is still room to fit a tool which is quite adequate.

The generation of screwthreads in the lathe is essentially a jobbing task; it is rarely, if ever, used in quantity production as it is far too slow to suit general requirements. Except in high precision toolroom work, such as the production of screw pitch gauges, exact measurement of all thread dimensions is seldom made. Most of us, having turned the screw blank, or bored the tapping hole, to nominal dimensions, work by “fit and feel,” either to a gauge or to the mating part, rather than by precise measurement. Complete specifications of thread dimensions are sometimes very complicated, as anyone will discover who looks up the BS figures. Quite apart from the hundreds of different thread pitches, there are over 180 thread forms (flank angle, root and tip radius, and effective depth) in use at present.

As a general guide for those who are mainly interested in cutting threads to Whitworth form (which embraces BSF, BSP, brass pipe, and several other British Standard pitches) the depth of thread is approximately 0.64 of the pitch. Thus for 16t.p.i., the depth of thread is

It is assumed that the radius at the tip of the tool is in exact proportion to the pitch, but this is very difficult to ensure, especially when allowance for wear of the tool point must be taken into account. There is some latitude in the fit, and even the form, of most threads, and it is better to have too fine a radius than otherwise.

Unless specially ground tools for every pitch of thread are used, it is impossible to work to dead measurement of the thread depth on this assessment. The threads are therefore usually finished with chasers.

Hand and machine chasers are essentially multi-toothed form tools, of correct form and pitch for various threads. Generally speaking, machine chasers are not suited for use on light lathes; in any event they are relatively expensive, and a set of them, both outside and inside, to cover the range of pitches likely to be used would be beyond the resources of most amateur workshops. Hand chasers are cheaper and will cover most requirements in light engineering.

In the past, chasers have been much used for cutting threads from the solid blank, on lathes not otherwise equipped for screwcutting. Skill is required to manipulate them, as they must be presented to the work in a sweeping movement, related to the pitch of the thread and the speed of the lathe. Until such skill is attained, many jobs are likely to be spoiled through incorrect tracking or drunken threads. The use of a chaser to finish the form and size of a thread already generated, at least partly, is much easier, and more appropriate to present-day practice. In common with other hand turning tools, chasers should be fitted with handles long enough to give plenty of leverage. They also call for the use of a tool rest, as close to the work as possible. Unless the standard form of T-rest is employed, a rigid bar must be