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Re: Non-Custer Carbines SN check

Posted by Pete Nelson on Friday, 12 November 2010, at 12:07 p.m., in response to Re: Non-Custer Carbines SN check, posted by JasonZ in MO on Friday, 12 November 2010, at 11:13 a.m.


The left-handed drill bit sounds like a great idea. I have a couple, but they are both "the larger sizes" (above 3/8" diameter). As far as 26-tpi taps, the only source I have seen at all recently is Keith Rush (at TRAPDOORS GALORE in Las Vegas) who used to advertise on his TRAPDOORS GALORE WebSite a specially-made set of (2) taps and (2) dies. They were, I believe, 0.187-26 and 0.195-26 andf ran $225.00 for the (4) pieces. I bought a set, and they have thus far worked fine for - - in most cases - - re-chasing existing Springfield Armory threads, although I have tapped several holes from scratch, using the closest correct size tap drill.

I measured as carefully as I could (using either my STARRETT electronic 1-inch digital micrometer and/or my STARRETT 6.0-inch analog caliper) most of the major thread sizes on the Springfields TRAPDOORS and made up a "use-at-your-own-risk" table of sizes.

The 0.187-26 thread was used on the:

Bridle screw, sear screw, and sear spring screw holes in the lock plate. The hammer screw (i.e., the female hole in the tumbler); the firing pin retainer screw; and the cam latch cover plate screw (i.e, the female hole in the side of the breech block for holding the cam latch cover plate).

I can't remember where the 0.195-26 thread was used (that is missing on the copy of my table tghat I was able to locate).

I believe that the (2) holes for the rear sight mounting screws was a 0.157-26.

The tang screw (the one which passes through the tang of the breech screw and down through the stock, finally threading into the trigger guard plate) is, I believe, a 0.212-26.

The two small screws holding the gib cover plate onto the slider of the M1879 "BUCKHORN" rear sight are, I believe, a 0.099-26 thread.

I will have to locate the original of my table which, I think, I had completed and have filed somewhere on my computer (in an EXCEL table).

I believe that Keith Rush stilol has his WebSite activated, but I will have to bring it up to see whether he still has those tap-and-die sets advertised.




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