Rebarrel small ring 95 mauser

[mickri]

I am hoping to finally start rebarreling my Chilean model 95 mauser actions this winter. Gunsmith Ron Henrickson who goes by Speerchucker on many forums has a long thread over on the gunsmithing forum where he gives the spec's on small ring mauser actions. He mentions that some have 55 degree whitworth and some have 60 degree imperial threads. I happen to have both imperial and whitworth thread gauges. I have tried both and can't really tell any difference in the fit. My plan is to do make a short test bar where I thread one end with 12tpi whitworth and the other end with 12tpi imperial to see which fits the best. I will have to grind a HSS whitworth tool bit. Any tips on how to grind this would be appreciated. Speerchucker also says the threads need to be a class 4 fit. How do you achieve a class 4 fit?

Thanks for any help you guys can provide.

 

[benmychree]

To grind the whitworth tool, all you need is a 55 deg. "center gage" or "fishtail". A real whitworth thread would have a radiused root and crest, but likely the one made would have a sharp root and truncated crest, although if you have a whitworth pitch gage you may be able to stone an approximate radius on the point of the tool.

 

[mickri]

I don't have 55 deg fishtail. I can make one. Especially since I finished the conversion of my dunlap band saw from wood to metal today.

 

[mickri]

Today's project was to turn down the end of a 1 1/4 round steel bar I had to .980 x .645 and then cut 12 tpi Imperial threads to see how it would fit. I didn't do it between centers because the piece was only 4" or so long. Other than not being between centers I did it just like I would if it was a barrel blank. Each threading pass was at .005. As I got closer to completing the threads I started doing test fits with the receiver. When the receiver screwed on about 3/4 of the way I did a cleanup pass without changing the depth of cut. The receiver now easily screwed on all of the way with a tight fit against receiver. I have no idea if this is a class 4 fit as Spearchucker recommended.

 

[mickri]

The above doesn't seem like a big project and it wasn't. The 3 jaw chuck that I grabbed to use felt a little gummy and stiff. Must of the morning was spent taking the 3 jaw apart and cleaning it.

 

[derf]

Class 4 means that there is approx .004" difference in pitch diameter from male to female threads. You have already figured out where you need to be, don't worry about the class of fit.
Typically barrel thread fits should be class 3 or better, but these 100 yr old war horses are usually rougher and inconsistent. With the larger thread pitch, a class 4 is sufficient.

 

[mickri]

Thanks derf. The issue that I am trying to determine is if the receiver threads are Whitworth or Imperial. My best guess is that male Imperial should not screw into female Whitworth because the 60 degree Imperial is wider than a 55 degree Whitworth thread. But maybe they are so close that the difference falls within the tolerance of the threads. I am going to do another test where I try to cut a 55 degree thread. I'll have to grind a 55 degree tool bit to do that.

When I do the actual barrel install I might use loctite on the threads. Haven't decided on that yet.

I have two of these actions. One will be a 257 Roberts. Haven't decided on the caliber for the other one. I already have a 6.5x55 swede so I don't need another one of those. I'll go through the SAAMI cartridge data to see what falls within an acceptable pressure range. These rifles were originally chambered for 7x57 and being made by Lowe in Germany I think that they are decent actions. The Spanish model 93's are a different story. I passed on those.

I also have a Carcano action. That action will get a 35 Remington barrel.

 

[mickri]

This morning I reground one of my 60 degree tool bits to 55 degrees and rounded the tip to fit in my whitworth thread gauge. Bit of background. The piece of steel I have been using was left over from when I made my QCTP. The finished end in the above picture I use to check the fit of tool holders to the post on my QCTP when I make a new tool holder. Didn't want to lose that so without hardly any drama I parted off that end. Parting is getting easier. Then turned the end down to .980 x .645 long and cut a groove for the thread to end into. Then proceeded to cut the 55 degree thread. At first the action would not even start to thread on. After a couple of more passes it started to thread on with what felt like a fairly tight fit. Did another pass and it screwed almost all the way on. Did a cleanup cut without changing anything and the action easily screwed all the way on with no difference in feel compared to the 60 degree threads. At this point I don't know if the action has whitworth or imperial threads.

 

[pontiac428]

Chilean receivers are an unexpected starting point, especially as a Mauser sporterization project on this side of the turn of the century. In the 1950s, this would have filled books and magazines, but now not so much. What is your intended purpose with these rifles as finished? Are they field guns mainly? I'm curious on your choice and what direction you are going. I love gun projects, I just gotta know if this is a work of madness or a work of genius!

 

[derf]

I suppose you could track those threads with some prussion blue.