Oops. Lathe workholding issues.

Right. Whitworth form, 55 degree thread, but 1/4-22.

I believe Mr. Mauser used the same screws as the Gew 88 in his 1891 design, his 1893 design(s), etc. all the way through his iconic 1898 rifle, and perhaps even beyond that. In 1888 I think there were significantly fewer notions about standardized threads. And switching tooling anytime between 1888 and 1945 (and even beyond) when these rifles were produced would simply have been inconvenient. Why bother? Well... Now I'm fabricating an entirely new screw because the commission in 1888 was two threads per inch off!

And I don't have the right die tooling, and have no intentions of either chasing down or purchasing at this point.
 
Interesting discussion on Barrel threads on Mauser's here:http://bbs.homeshopmachinist.net/archive/index.php/t-12291.html
Also could have been 7 mm Lowenhurz? That has a pitch of 1.1 mm and is actually only 0.001" bigger than 1/4" is reality. There are some old obscure Metric threads that use the Whitworth thread form just because it is so nice.
 

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NortonDommi said:
Interesting discussion on Barrel threads on Mauser's here:http://bbs.homeshopmachinist.net/archive/index.php/t-12291.html
Also could have been 7 mm Lowenhurz? That has a pitch of 1.1 mm and is actually only 0.001" bigger than 1/4" is reality. There are some old obscure Metric threads that use the Whitworth thread form just because it is so nice.
Click to expand...

That could be, I suppose. My calipers read .252 inch on my original screws. Which are beat up enough (and a hundred years old!) that I don't want to be dogmatic, but I suppose it is possible. I'm pretty sure the gun was actually built in imperial measurements though. Everything else is nicely configured for English measurements. A hundred years (or more) after his guns were built, I don't think Mr. Mauser could have foreseen the problems I'm having with his gun! If he thought it would even be around!
 
Regardless you have got it done and I'm sure Mr Mauser will shower blessings upon you for your diligence in keeping it original.
One of my greatest challenges and greatest joys is finding out what obscure thread may have been used. Still a lot of very industry specific ones in use to keep life interesting even if annoying in that you can't just pop down to the local hardware store for a replacement. Where I live I am increasingly encountering fastner salesmen that don't know anything but ISO Metric exists, let's hope they never buy a Peugeot!
 
It's true, there were literally dozens of thread pitches in 1/4" size, most never seen now according to my pocket reference
 
Okay, made some chips. And one of my screws goes in the recycle bucket (that's okay! They are cheap, and came in a ten pack :D )

Any ideas on how to hold the socket head tightly enough not to wobble and still have room to get in there with a tool to do some cutting? I thought about my steady rest but it is WAY too big to stick on the head of the screw and still get a cutting tool in there.

Also, how do I make sure the socket head is concentric with the rest of the screw? My first operation was to cut the head down to the size I wanted. I chucked the threaded shank in my three jaw (and some of my problem is here, no doubt), and then when I pulled it out and looked at it, it *looks* like the socket is not quite in the center of the head. I put an indicator on a chucked reamer shank close to the diameter of my screw to look at my chuck runout, and I've got about .0025 between high and low, and my guess is that the "normal" human eye would never notice that much (or little) lack of concentricity. I'm thinking the screw threads are not really perfect, but I don't know what else I can trust. I've got to hold it somehow to center drill it (chucked, held by the threads, ostensibly) and I'm thinking that even if the threads aren't perfect, they are probably better than the sloppiness between the driver bit and and socket head.

Using the bit to drive the screw worked majestically, by the way, so I'm not trying to spit on that idea or anything, I just need an idea to make it tighter! Or another way to center it and still use the hex to drive it. Like maybe a hex bit with a point on it. Although I've breathed out anathemas upon Phillips and his screws before, I'm beginning to see the advantage his design has for driving screws on lathes!

Or, maybe it's just an optical illusion having to do with the domed head and six points of the socket and the lighting. Or maybe I just need to get over it even if it isn't an illusion.

But... PERFECTION! AAAHHH!!!!

What do ya'll think?
 
Mass produced screws aren't machined, the threads are rolled & the heads are hot formed so they won't be perfectly concentric. You can use tape or paper to make the hex bit fit tighter. Not sure how much play you have. Can even super glue it, heat will release it afterwards.

If you really need it to be precise, make your own hex mandrel to drive the screw. That way you can machine the hex to be a tight fit & chuck it in a 4-jaw if you want it to run true with the OD of the head.
 
Mauser lover said:
Yes, pure genius.

And I even have one that is set in a socket for a quarter drive. Being round, I might be able to manipulate that to fix any concentricity issues. Of course, that might not work, but it's a possibility. I'm a little concerned about slop between the bit and the socket in the screw, but I'm guessing it will work out fine.
Click to expand...

Set it up in the lathe, and hit it with some Locktite Superglue, or some of the girlfriends ( or your own) fingernail polish. Acetone/heat will release when done.

and darkzero, I'll have your baby, you clever thang you. Brilliant.
 
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