ACME Threading

Al Flipo,

I don't know where my Garand and M14 receiver blueprints are right now, but I do believe it's 10 TPI. Definitely Acme thread, though. The most common non-regular Acme is called "Stub Acme", which is essentially a shallower Acme form. Some large engineering/manufacturing interests also have their own proprietary variants to better suit their particular requirements.

When I said earlier that Acme is not uncommon in firearms, I should have said "was" not uncommon. I don't know how many modern firearms use it, as my primary interest is in older milsurps.

Cheers,
Michael in Edmonton
 
If i look at the p14 action i have on hand it looks like the threads have square sides ,therefore square threads ..... if i look in the machinery's handbook it states that the angle of an Acme thread is 29 deg measured in an axial plane therefore not a square thread . It also says that the stub acme is the same acme thread only shallower used in applications where a course pitch shallow thread is needed...
OK i read further , it says Quote " The square thread form has a pitch about twice that of unified threads , the thread is difficult to produce economically because of its perpendicular sides and has largely been replaced by the acme form of thread in most applications .."
So now i know too....
Machinery's handbook best investment in my toolbox... :)
 
I just had my Garand re-barreled and the threads where very shallow, 10 tpi and looked square to me. I didn't do and in depth examination, but I've cut acme before (not stub acme though) and they didn't look like one
 
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