Thread Cutting on the lathe

Reference chart for the depth to feed tool when cutting American threads.

Thread Cutting on the lathe

Depth to feed tool when cutting American threads

National coarse and fine

Threads per inch Depth of thread 1 Double depth of thread Feed depth compound at 30° 2 Width of flat Threads per inch
2 0.3247 0.64950 0.3749 0.0625 2
2 1/4 0.2887 0.5773 0.3334 0.0556 2 1/4
2 3/8 0.2735 0.54694 0.3158 0.0526 2 3/8
2 1/2 0.2598 0.51960 0.3000 0.0500 2 1/2
2 5/8 0.2474 0.49485 0.2856 0.0476 2 5/8
2 3/4 0.2362 0.47256 0.2727 0.0455 2 3/4
2 7/8 0.2259 0.45182 0.2608 0.0435 2 7/8
3 0.2165 0.4330 0.2500 0.0417 3
3 1/4 0.1998 0.39966 0.2307 0.0385 3 1/4
3 1/2 0.1856 0.37114 0.2143 0.0357 3 1/2
4 0.1624 0.32475 0.1875 0.0312 4
4 1/2 0.1443 0.28869 0.1667 0.0278 4 1/2
5 0.1299 0.2598 0.1500 0.0250 5
5 1/2 0.1181 0.23618 0.1363 0.0227 5 1/2
6 0.1083 0.2165 0.1250 0.0208 6
7 0.0928 0.18557 0.1071 0.0178 7
8 0.0812 0.16237 0.0937 0.0156 8
9 0.0722 0.14433 0.0833 0.0139 9
10 0.0650 0.1299 0.0750 0.0125 10
11 0.0590 0.11809 0.0682 0.0113 11
11 1/2 0.0564 0.11295 0.0651 0.0108 11 1/2
12 0.0541 0.10825 0.0624 0.0104 12
13 0.0500 0.09992 0.0577 0.0096 13
14 0.0464 0.09278 0.0535 0.0089 14
15 0.0433 0.08660 0.0499 0.0083 15
16 0.0406 0.08118 0.0469 0.0078 16
18 0.0361 0.07216 0.0417 0.0069 18
20 0.0325 0.06495 0.0375 0.0062 20
22 0.0295 0.05904 0.0340 0.0056 22
24 0.02706 0.05412 0.03122 0.0052 24
26 0.02498 0.04996 0.0288 0.0047 26
27 0.02405 0.04811 0.0277 0.0046 27
28 0.02319 0.04639 0.0267 0.0044 28
30 0.02165 0.04330 0.0249 0.0041 30
32 0.0203 0.04059 0.0234 0.0039 32
34 0.0191 0.03820 0.0220 0.0036 34
36 0.01804 0.03608 0.0208 0.0034 36
38 0.01709 0.03418 0.0197 0.0032 38
40 0.0162 0.03247 0.0187 0.0031 40

Footnotes

1. Single depth of thread = 0.6495/N where N is threads per inch
For N=8, Single depth=0.6495/8=0.0812
2. Feed depth with compound at 30° = sec30x(single depth of thread) {=1.1547x(0.6495/N) or 0.75/N}
For N=8, Feed depth =1.1547x(0.6495/8) {=1.1547x0.0812=0.0937}, or Feed depth=0.75/8=0.0937


Keywords:
lathe thread cutting threading chart reference 
Doc ID:
81932
Owned by:
Eric E. in ECB Shops Documentation
Created:
2018-04-27
Updated:
2019-07-02
Sites:
ECB Shops Documentation