Lister 5/1 Diesel

Threading Tables

Chart No 15 - British Standard Worm Threads


This thread is similar in form to the Acme Thread, in that the included angle is 29 degrees, but the depth of the thread is greater.
The width of the flat at both top and bottom are therefore different. The table below gives full machining details.

Worm Threads (29 Deg Thread Angle) - NOT Acme
Dimensions in Inches except where stated

Thread Form Data
T.P.I. Pitch Addendum Thread Depth below
pitch line
Total Thread
Depth
Tooth Thickness
at pitch line
Top Thread
Width
Bottom Thread
Width
1 1.000 0.3183 0.3683 0.6866 0.5000 0.3354 0.3100
0.6677 0.2122 0.2455 0.4577 0.3333 0.2236 0.2066
2 0.5000 0.1592 0.1841 0.3433 0.2500 0.1677 0.1550
0.4000 0.1273 0.1473 0.2746 0.2000 0.1341 0.1240
3 0.3333 0.1061 0.1228 0.2289 0.1667 0.1118 0.1033
0.2857 0.0909 0.1053 0.1962 0.1429 0.0958 0.0886
4 0.2500 0.0796 0.0920 0.1716 0.1250 0.0838 0.0775
0.2222 0.0707 0.0818 0.1526 0.1111 0.0745 0.0689
5 0.2000 0.0637 0.0736 0.1373 0.1000 0.0670 0.0620
6 0.1667 0.0531 0.0613 0.1144 0.0833 0.0559 0.0516
7 0.1429 0.0455 0.0526 0.0981 0.0714 0.0479 0.0443
8 0.1250 0.0398 0.0460 0.0858 0.0625 0.0419 0.0387
9 0.1111 0.0354 0.0409 0.0763 0.0556 0.0373 0.0344
10 0.1000 0.0318 0.0369 0.0687 0.0500 0.0335 0.0310
12 0.0833 0.0265 0.0307 0.0572 0.0416 0.0279 0.0258
14 0.0714 0.0227 0.0263 0.0490 0.0357 0.0239 0.0221
16 0.0625 0.0199 0.0230 0.0429 0.0312 0.0209 0.0194
18 0.0556 0.0177 0.0205 0.0382 0.0278 0.0186 0.0172
NOTES:- Depth of Thread = 0.6866 X Pitch
Width at Top of Thread = 0.335 X Pitch
Width of Space at Bottom of Thread = 0.310 X Pitch
Width of Thread at Pitch Line = 0.5 X Pitch
Addendum = 0.3194 X Pitch


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