M48 thread question

[usgicollector]

Does anyone know where or who has a tap for the treaded boss on the front of the receiver. I believe it is 1/4 22 or could be a odd metric size.
The bolt broke off and I got the remains out, but the threads are buggered up where it broke and the new bolt will not thread in all the way. I know the the bolt is not the problem as it will thread all the way through the rear receiver threaded hole. Sorry if this is a question that is a little odd. I am into garands and carbines, so I don't know where to look for mauser parts.

Thanks
Dave

Information

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[jmoore]

The front action/ trigger guard screw? 1/4"-22 would be really odd. Its probably regular metric, but I'm not the best one to ask. Just trying to make sure we know exactly with which part you're having dramas.

[usgicollector]

I believe we are talking about the same screw, The shorter or front screw that holds the trigger guard to the receiver.
I miked it at .246 and the thread pitch is 22 dead on .
I am a machinist and I know that is not a standard thread size.
It could also be a 6.25 MM but no metric thread pitch on my gauge fits.
I found an obscure post on gunboards and they were talking about the threads on the barrel and trigger guard being a english measurement and the bolt, and other threaded items being metric.
I found that brownells sells a 1/4 -22 tap in all 3 tap types, so I figure it must be somewhat common in the gunsmithing world, but not in industry because Mcmaster Carr, Grainger, and MSC do not stock them.

If that is the correct thread pitch I will just buy the tap, but I was hoping hat a (mausersmith) could give me conformation that that is indeed the correct size.
Thanks
dave

[jmoore]

Welcome to the weird world of Gun Screws! You might try this post in the Gunsmithing Forum if none of the Mauser guys steps up. Mausers really aren't my speciality, sorry!

[Patrick Chadwick]

See my answer under "1909 Mauser Trigger Guard Screws". Yes, it does indeed seem to be 1/4" x 22 tpi, but I have not yet seen any original documentation.

Considering that the barrel threads are 12 tpi (and Whitworth form, no less!) it is odd, but quite possible. It may have been done deliberately to make sure than only correct screws would fit!

Patrick

[Patrick Chadwick]

P.S: If you think you've got problems, try the Enfield screws!

Patrick

[Jim]

See my answer under "1909 Mauser Trigger Guard Screws". Yes, it does indeed seem to be 1/4" x 22 tpi, but I have not yet seen any original documentation.

Considering that the barrel threads are 12 tpi (and Whitworth form, no less!) it is odd, but quite possible. It may have been done deliberately to make sure than only correct screws would fit!

Patrick

Here's original documentation for you. These are from working drawings for the Yugo model 1924, courtesy and with permission of Branko Bogdanovic, author "Serbian & Yugoslav Mauser Rifles," and Zastava historian.

The image was too large so I had to split it in two. I believe the items circled in red are what you're looking for?

[jmoore]

And Whitworth (55 degree thread form w/ rounded crests and roots) to boot! It must be a long running devious plot of the screwmaker's guild...How VERY strange.


BTW, 6.35mm works out to 0.250".

ETA: Thanks, Jim! That will keep me amused and bemused for some time.

[Jim]

Now, I don't know if this is what they used, but the Whitworth thread lends itself nicely to press threading. I'm darned if I remember the correct term (and I was a machinist too) but how it worked was instead of cutting the thread into the metal, it literally pressed the metal around the thread deeper. This has an advantage of making a very strong threaded hole since the molecules are compressed making the steel (and whatever else) denser around the tap making that local area extremely tough.

Whatever the case, you're quite welcome to the information.