Gentlemens:
Non standard threads are not at all uncommon in anything made before the second war. It is particularly common in guns made before the first.
Originally it was because there were no standards and all the thread cutting tooling was shop made. When standards were introduced there was still all the old tooling around, and the makers were not going to throw it away just because someone came up with a standard. Plus, if you had been using a thread equivalent to a #10-30 for the last 20 years in all your guns, it would be burdensome to switch to the standard #10-32. Now you have to have two sets of tooling, one to maintain old work and one to make new.
Even when the standards were well established, there was still an advantage to non standard or "proprietary" (often called Bastard) screw threads. You have to go the manufacturer for parts. This practice is about gone now.
As for timing the screw head, it is a fairly simple process. If you have 32 pitch thread (32 threads per inch) one complete revolution will create an axial movement of 1/32", or about .032". Half a turn would equal .016" and a quarter turn .008"
If the slot on you 32 pitch screw head lines up at 8:00 and you want it to line up at 9:00 you need to take one hour's metal off the back.
.032 divided by 12 = .0026" This is what you would have to take off the back of the screw head to bring it into time.
Best to all,
Glenn
Last edited by Glenn Fewless; 03-29-2010 at 04:25 PM..
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03-29-2010, 04:25 PM
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