P-14 Volley sight screw

Al Flipo

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Someone asked me to make a replacement screw for a P-14 volley sight.
I have never come across a 26-1/3 TPI size in my life, and I have been doing it for a long time.
Looking further in to this, and, low and behold, there are all sorts of wacky insane thread sizes on these English rifles.
What were these old guys thinking to come up with craziness.
Anyway, 26 TPI did the trick just fine, a little bit of cold blue and it looks factory made.
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I am quite sure that thread is from the Enfield series of threads - virtually obsolete now, but apparently not during WWI when Enfield Armoury still influencing stuff. Could not find reference to that thread series (with other sizes and thread per inch counts), being used anywhere other than Enfield Armoury in England. Patrick Chatwick on Milsurps has a post of various other more "modern" threads that might be made to "work" in place of the old Enfield series. As per that picture that you posted - notice how the thread form has such as "strange-to-us" angle!!! And, FYI - "Pattern 1914 and U.S. Model of 1917" by Charles Stratton, page 94, says that the "dial sight fixing screw" is 0.17" diameter, 1.75" long, 37 tpi domed fillister head. I have no clue where he got his information.
 
Like to have got his info by finding the closest pitch he could, measuring off one or more parts.

Winchester did the same sort of thing. Thread pitches designated in halves of a TPI. Most folks just assumed the ones they had were just 'off' a bit, until the prints were found.

It's a easy way to make the customer come back to you and you alone, when they are looking for parts. Sewing machines are just FULL of similar unique combinations of thread pitch and diameter.
 
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