Screw-Cutting By Self-Acting Lathe. Part 3
Description
This section is from the book "Turning Lathes", by James Lukin. Also available from Amazon: Turning Lathes: A Guide to Turning, Screw Cutting, Metal Spinning and Ornamental Turning.
Screw-Cutting By Self-Acting Lathe. Part 3
The greatest care is necessary to set the tool exactly at right angles to the axis of the work, in order that the thread shall be upright, not sloping like saw teeth, or when the screw and nut are cut, though both of one diameter and
SCREW-CUTTING BY SELF-ACTING LATHE. Ill pitch, they will not fit each other. And in grinding the tool, in the case of Whitworth V-shaped threads, see that the correct angle of 55° is maintained. In V threads it is not usual to give the tool any rake or slope; but clearance is necessary, or the under part of the cutting point of the tool may scrape and spoil the thread. But in cutting square threads, especially if coarse or double threads, it is necessary to form the tool with a rake or slope, to follow in the space cut by the edge, either inclining to right or left, as the case may be. To get the correct angle of this rake, draw a right-angled triangle, having the pitch for a base, the circumference of screw for perpendicular, and the hypothenuse will then be the required angle. For all the above purposes, a very useful little gauge is sold, invaluable to screw-cutters, costing only about 3s. It may be observed, that in square threads the depth is usually half the pitch of thread.
Appended are some calculated tables of change wheels which may save time and trouble. To these we have already referred on page 95, pointing out the use or abuse of them. They are certainly an assistance to a young workman, enabling him to set the proper wheels for the job in hand, and to go confidently to work. But if, on trial, some error is found to exist, he will probably be unable to rectify it, and his work may prove to be spoilt, just as it was almost finished. It is a better plan, even where such tables are hung up in a workshop for reference, to make an apprentice work the sum first of all, and then compare the result with the figures given - he will soon find himself independent of such aid, and will leave the tables for those too lazy or too indifferent to make the calculations for themselves.
Tables Of Change Wheels. I. - Leading Screw Having Two Threads Per Inch
No. of Threads per in. | Drivers. | Driven. | |||
1 | 40 | - | .. | - | 20 |
50 | - | .. | - | 25 | |
60 | - | .. | - | 30 | |
1 ¼ | 40 | - | .. | __- | 25 |
30 | 40 | .. | 15 | 50 | |
1½ | 40 | - | .. | - | 30 |
40 | 60 | .. | 20 | 90 | |
40 | 50 | .. | 25 | 60 | |
1¾ | 40 | - | .. | _- | 35 |
20 | 40 | .. | 20 | 35 | |
2 | 40 | - | .. | - | 40 |
60 | - | .. | - | 60 | |
2¼ | 40 | -__ | .. | _- | 45 |
20 | 80 | .. | 30 | 60 | |
2i | 40 | - | .. | - | 50 |
20 | 90 | .. | 30 | 75 | |
2¾ | 40 | - | .. | - | 55 |
60 | 40 | .. | 30 | 110 | |
3 | 20 | - | .. | - | 30 |
40 | - | .. | - | 60 | |
25 | 40 | .. | 20 | 75 | |
50 | 40 | .. | 30 | 100 | |
3½ | 20 | - | .. | - | 35 |
40 | - | .. | - | 70 | |
20 | 80 | .. | 40 | 70 | |
4 | 20 | - | .. | __ | 40 |
40 | -- | .. | - | 80 | |
20 | 60 | .. | 30 | 80 | |
5 | 20 | - | .. | - | 50 |
30 | - | .. | - | 75 | |
40 | - | .. | - | 100 | |
25 | 60 | .. | 75 | 50 | |
6 | 20 | - | .. | - | 60 |
20 | 50 | .. | 40 | 75 | |
50 | 40 | .. | 75 | 80 | |
No. of Threads per in. | Drivers. | Driven. | |||
7 | 20 | - | .. | - | 70 |
30 | - | .. | - | 105 | |
30 | 40 | .. | 60 | 70 | |
8 | 20 | - | .. | - | 80 |
25 | - | .. | - | 100 | |
50 | 20 | .. | 40 | 100 | |
9 | 20 | - | .. | _- | 90 |
20 | 50 | .. | 75 | 60 | |
20 | 100 | .. | 75 | 120 | |
10 | 20 | - | .. | - | 100 |
20 | 40 | .. | 50 | 80 | |
30 | 40 | .. | 75 | 80 | |
11 | 20 | - | .. | - | 110 |
20 | 50 | .. | 100 | 55 | |
20 | 40 | .. | 55 | 80 | |
12 | 20 | - | .. | - | 120 |
20 | 25 | .. | 50 | 60 | |
20 | 50 | .. | 100 | 60 | |
13 | 20 | 25 | .. | 65 | 50 |
20 | 30 | .. | 65 | 60 | |
20 | 50 | .. | 65 | 100 | |
14 | 20 | 30 | .. | 60 | 70 |
20 | 50 | .. | 100 | 70 | |
20 | 60 | .. | 120 | 70 | |
15 | 20 | 40 | .. | 50 | 120 |
20 | 30 | .. | 50 | 90 | |
20 | 60 | .. | 90 | 100 | |
16 | 20 | 50 | .. | 80 | 100 |
20 | 25 | .. | 40 | 100 | |
30 | 25 | .. | 60 | 100 | |
17 | 20 | 50 | .. | 85 | 100 |
20 | 25 | .. | 50 | 85 | |
20 | 60 | .. | 85 | 120 | |
18 | 20 | 40 | .. | 80 | 90 |
20 | 50 | .. | 120 | 75 | |
20 | 60 | .. | 120 | 90 | |
No. of Threads per in. | Drivers. | Driven. | |||
19 | 20 | 40 | .. | 80 | 95 |
20 | 50 | .. | 95 | 100 | |
20 | 20 | 40 | .. | 80 | 100 |
20 | 60 | .. | 120 | 100 | |
21 | 20 | 25 | .. | 75 | 70 |
20 | 30 | .. | 90 | 70 | |
22 | 20 | 40 | .. | 80 | 110 |
20 | 30 | .. | 120 | 55 | |
23 | 20 | 50 | .. | 115 | 100 |
20 | 60 | .. | 115 | 120 | |
20 | 45 | .. | 90 | 115 | |
24 | 20 | 40 | .. | 80 | 120 |
20 | 30 | .. | 80 | 90 | |
20 | 45 | .. | 120 | 90 | |
25 | 20 | 30 | .. | 75 | 100 |
26 | 20 | 30 | .. | 120 | 65 |
27 | 20 | 40 | .. | 120 | 90 |
20 | 25 | .. | 75 | 90 | |
No. of Threads per in. | Drivers. | Driven | |||
28 | 20 30 | .. | 105 | 80 | |
20 | 45 | .. | 105 | 120 | |
20 | 25 | .. | 70 | 100 | |
30 | 20 | 30 | .. | 90 | 100 |
20 | 25 | .. | 75 | 100 | |
20 | 40 | .. | 100 | 120 | |
32 | 20 | 25 | .. | 80 | 100 |
20 | 30 | .. | 80 | 120 | |
25 | 30 | .. | 100 | 120 | |
34 | 20 | 30 | .. | 85 | 120 |
20 | 25 | .. | 85 | 100 | |
36 | 20 | 25 | .. | 90 | 109 |
20 | 30 | .. | 90 | 120 | |
38 | 20 | 25 | .. | 95 | 100 |
20 | 30 | .. | 95 | 120 | |
40 | 20 | 30 | .. | 100 | 120 |
48 | 20 | 25 | .. | 100 | 120 |
60 | 20 | 30 | .. | 120 | 150 |
II. - Leading Screw Having Four Threads Per Inch
1 | 80 | - | .. | -- | 20 |
60 | 100 | .. | 30 | 50 | |
50 | 120 | .. | 20 | 75 | |
l¼ | 80 | - | .. | - | 25 |
40 | 80 | .. | 20 | 50 | |
1½ | 80 | - - | .. | - | 30 |
40 | 120 | .. | 30 | 60 | |
40 | 90 | .. | 30 | 45 | |
1¾ | 80 | - | .. | - | 35 |
40 | 80 | .. | 20 | 70 | |
60 | 80 | .. | 20 | 105 | |
2 | 40 | - | .. | - | 20 |
50 | - | .. | - | 25 | |
2¼ | 80 | - | .. | - | 45 |
40 | 80 | .. | 60 | 30 | |
2½ | 80 | - | .. | - | 50 |
40 | 90 | .. | 30 | 75 | |
60 | 90 | .. | 45 | 75 |
2¾ | 80 | - | .. | - | 55 |
40 | 50 | .. | 25 | 55 | |
50 | 80 | .. | 110 | 25 | |
3 | 60 | - | .. | - | 45 |
40 | - | .. | -- | 30 | |
50 | 40 | .. | 20 | 75 | |
3½ | 40 | - | .. | - | 35 |
60 | 50 | .. | 35 | 75 | |
80 | 50 | .. | 35 | 100 | |
4 | 40 | - | .. | - | 40 |
60 | - | .. | - | 60 | |
5 | 40 | - | .. | - | 50 |
60 | - | .. | -- | 75 | |
60 | 30 | .. | 25 | 90 | |
6 | 60 | - | .. | - | 90 |
30 | -- | .. | - | 45 |
No. of Threads per in. | Drivers. | Driven. | |||
7 | 40 | - | .. | - | 70 |
20 | - | .. | - | 35 | |
45 | 80 | .. | 90 | 70 | |
8 | 20 | - | .. | - | 40 |
30 | 75 | .. | 45 | 100 | |
9 | 20 | .. | - | 45 | |
30 | 80 | .. | 60 | 90 | |
30 | 40 | .. | 60 | 45 | |
10 | 30 | - | .. | - | 75 |
40 | - | .. | - | 100 | |
30 | 40 | .. | 60 | 50 | |
11 | 20 | - | .. | - | 55 |
30 | 40 | .. | 60 | 55 | |
12 | 20 | - | .. | - | 60 |
30 | 50 | .. | 45 | 100 | |
13 | 20 | - | .. | - | 65 |
25 | 40 | .. | 50 | 65 | |
14 | 20 | - | .. | - | 70 |
20 | 50 | .. | 35 | 100 | |
20 | 60 | .. | 35 | 120 | |
15 | 20 | - | .. | - | 75 |
30 | 40 | .. | 90 | 50 | |
10 | 25 | - | .. | - | 100 |
30 | 50 | .. | 60 | 100 | |
17 | 20 | - | .. | - | 85 |
35 | 40 | .. | 70 | 85 | |
18 | 20 | - | .. | - | 90 |
30 | 40 | .. | 60 | 90 | |
25 | 40 | .. | 45 | 100 | |
19 | 20 | - | .. | - | 95 |
25 | 80 | .. | 100 | 95 | |
25 | 40 | .. | 50 | 95 | |
20 | 20 | - | .. | - | 100 |
25 | 40 | .. | 50 | 100 | |
25 | 60 | .. | 75 | 100 | |
21 | 20 | - | .. | - | 105 |
20 | 40 | .. | 70 | 60 | |
No. of Threads per in. | Drivers. | Driven | |||
22 | 20 | - | .. | -- | 110 |
20 | 40 | .. | 55 | 80 | |
20 | 50 | .. | 55 | 100 | |
23 | 20 | - | .. | ., | 115 |
30 | 60 | .. | 115 | 90 | |
30 | 80 | .. | 115 | 120 | |
24 | 20 | - | .. | - | 120 |
25 | 40 | .. | 75 | 90 | |
25 | 20 | 40 | .. | 50 | 100 |
20 | 60 | .. | 75 | 100 | |
26 | 20 | 40 | .. | 65 | 80 |
20 | 35 | .. | 65 | 70 | |
27 | 20 | 40 | .. | 60 | 90 |
20 | 80 | .. | 90 | 120 | |
20 | 70 | .. | 90 | 105 | |
28 | 20 | 60 | .. | 70 | 120 |
20 | 40 | .. | 70 | 80 | |
30 | 40 | .. | 80 | 105 | |
30 | 20 | 40 | .. | 60 | 100 |
30 | 40 | .. | 100 | 90 | |
20 | 50 | .. | 75 | 100 | |
32 | 20 | 30 | .. | 80 | 60 |
20 | 60 | .. | 80 | 120 | |
25 | 40 | .. | 80 | 100 | |
34 | 20 | 50 | .. | 85 | 100 |
25 | 40 | .. | 85 | 100 | |
30 | 40 | .. | 85 | 120 | |
36 | 25 | 40 | .. | 90 | 100 |
30 | 40 | .. | 90 | 120 | |
38 | 25 | 40 | .. | 95 | 100 |
30 | 40 | .. | 95 | 120 | |
40 | 20 | 40 | .. | 80 | 100 |
20 | 30 | .. | 75 | 80 | |
48 | 20 | 25 | .. | 75 | 80 |
25 | 30 | .. | 75 | 120 | |
60 | 20 | 25 | .. | 75 | 100 |
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