Home Forums Hunting & Shooting Gunsmithing How to chase threads in Argentine Carbine nosecap?

Bear with me, this will be a little wandering because I don't know what I'm doing.

I purchased a nosecap and attaching screw for an Argentine 1909 Cavalry Carbine. The screw would thread in to the threaded hole in the nose cap quite freely from either side, but then stop. It didn't grind to a stop, it just went to a certain point and stopped right there. There must be a burr or rust or something right at that one point in the nosecap threads.

I tried to worry the screw past that point but the screw was practically putty-soft and broke off. I think I can get the broken piece out without further damage, but I'm wondering how to chase these threads to make the nosecap useable.

First thought: If it was a readily identifiable screw thread, I would buy a tap and run it through. Is there any hope the thread in the screwhole in the nosecap of a 1909 Argie Carbine is identifiable? A tap obtainable?

I haven't entirely given up on the above approach - I'm waiting to see if Kunhausen might note this - but I'm sort of expecting I won't be able to get the right tap. So...:

Second thought: If this was a car or truck such as I learned to work on in younger days ('50s, '60s, '70s GM, Mopar or Ford), I am sure a good old American made screw of the right size would be much stronger that the surplus screw I had and that I could chase this hole with one or more sacrificial screws.

I have ordered two more surplus screws. Does anyone have any ideas on a way to harden the extra screw and make an improvised chasing tap out of it? If I slightly tapered the last 1/16 of the screw, carefully filed a couple of lenghthwise notches into the last couple of threads and then hardened the screw with Casenit or by some other method (suggestion on method?), would I have a workable solution?

Can anyone suggest a good way to solve this?

TIA

Get the od and pitch of the new screws and try to match up to a tap if possible. Trying to use casenite will probably deform the treads enough to really mess them up. When you get the pitch and od, pm me as I have alot of odd taps and would send one to borrow if I have it.....Russ

Thanks, Russ! I'll reply when the after screws arrive.

That would work. Also you could have a thread turned on a lathe to match. Using a longer, more easily turned in and out bolt, with a groove along it's threaded length might chase the threads.

Solved! Thanks, all!

I remembered that my local Ace Hardware expanded their selection of metric fasteners so I took the nosecap to Ace. A M4 .70 screw really wanted to fit but would only go in about a thread and a half from either side.

The new screws arrived from Springfield Sporters. Same diameter on the threads as the Ace screw - within about a thousandth - and the threads meshed perfectly when held up against a light with my reading glasses on. Same result - the supposedly original screws only went in about a thread and a half.

So I start thinking that maybe these are repro screws using a modern thread that struck someone as about right. (Shouldn't be. Not from from Springfield Sporters. But I was wondering.) So I whittled down a hardwood dowel and forced it to thread into the hole in the nosecap to get an inpression of the thread pitch to compare to the screws. With my reading glasses and a magnifying glass and all the squinting I could muster, I could not find any difference in the thread pitch.

So I used force. I had a nice strong modern screw in hand, so I put a screwdriver on it and made it thread into the nosecap. Resistance was moderate but did not increase with depth. I withdrew the screw and saw little distortion of the threads - maybe a sort of sharpening of the thread edges but no stripping. So I chucked that two inch screw into an electric drill and screwed it in and out about 30 times.

Viola! Beautiful threads in the nosecap. Lots of black dust. I think Argentina re-parked this nosecap and clogged up those interior threads. The screw from Springfield Sporters fits very nicely now.

So I can say with some authority that the thread for the retaining screw in an original German-manufactured 1909 Argentine nosecap is M4 .70

good for you! Usually the pita problems have a simple answer