Cartridge holder for lathe

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SteveM
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Cartridge holder for lathe

Post by SteveM » Sun May 10, 2020 9:00 am

I sold a Sherline to someone who reloads.

He needed to do some case trimming, and I figured that if he had soft jaws we could machine the jaws to hold the cases, but it doesn't have two-piece jaws.

Is there a fixture for holding cartridge cases (or some other method) that would hold them accurately and repeatably so that he can use it to trim cases?

Either something that could mount in the chuck or directly to the spindle?

Steve

Harold_V
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Re: Cartridge holder for lathe

Post by Harold_V » Mon May 11, 2020 1:13 am

Case trimming is generally accomplished by holding the cartridge in a sleeve, which presents the cartridge end to the cutter at the proper attitude. If one has a stop in the back of the chuck (or better yet, soft jaws with a shoulder), the setup you described could be a solution to trimming, although I'd be hard pressed to say it could be done without a holding device like the sleeve I mention, below.

I make cases for two of my rifles, using similar cases, but longer. One of them is a 6MM Winchester cartridge, but the barrel, when installed by the maker, was not seated correctly, so the cartridges are made several thou longer to provide acceptable headspace. For it, I can use 30-06, 270 and similar cases to make the brass, so long as they are long enough. The other is a 17-222, for which commercial cartridges aren't commonly found, so I make them from 223 military brass, which I have by the thousands. Both of these cartridges need trimming after forming, so I use my Wilson case trimmer, along with the prescribed sleeve. I use a drill motor with a simple coupler to drive the trimming cutter, as I have to remove a lot of material. I can trim a cartridge in just a couple seconds with the drill motor.

Tapered cartridges can be installed in the sleeve by simply bumping the cartridge head on a wood or plastic surface. Once trimmed I use a rod, mounted in a base plate, and long enough to reach the internal base of the cartridge. To remove the cartridge from the sleeve it is placed over the rod and slammed down on the rod top.

For straight cartridges, like 38 Special, 357 Magnum as well as my 458 Winchester Magnum, I use a simple punch with my reloading press to install the cartridge, and the same punch to remove it from the sleeve. As all of this is located in the same proximity of the loading bench, it's actually quite fast and easy to do.

Yeah, I realize it's a lot more than you wanted to know, but, yes, a lathe can be easily used to trim cartridges, although it's a little overkill.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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SteveM
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Re: Cartridge holder for lathe

Post by SteveM » Mon May 11, 2020 7:26 am

Yea, the first thing that came to mind was soft jaws. It was literally "Yea we could to that with soft jaws... oh, wait, you don't have soft jaws".

I had thought of providing support with a steady rest. I though of a solid ring with a hole sized to a cartridge that you just slid back to the point where it contacts either the taper of the body or the taper of the shoulder. I was wondering if delrin AF would work, or would it get too hot and ooze.

We could get a collet and stick a pin it it to act as a stop

Steve

Harold_V
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Re: Cartridge holder for lathe

Post by Harold_V » Mon May 11, 2020 4:43 pm

I can see where the use of a steady could be beneficial and could replace the use of the sleeve normally used. Delrin AF would be quite acceptable, assuming the cut wasn't prolonged, and it most likely wouldn't be. The steady could be placed just behind the shoulder, which would provide plenty of support. Tool geometry would be critical, to avoid hogging (zero, or very little positive rake).

H
Wise people talk because they have something to say. Fools talk because they have to say something.

dwebster299
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Re: Cartridge holder for lathe

Post by dwebster299 » Fri May 15, 2020 12:22 pm

This seems like a ton of extra work to trim cases when a Wilson style case trimmer will do the same job, better, faster and a heck of a lot easier. I went down this rabbit hole and finally saw the light after weeks of trying different set ups in both the mill and the lathe. I made case holder sleeves, a quick release lever, micrometer stops for length etc. I tried my Dads Wilson trimmer clone (he modified his with a micrometer head for depth of cut) and it was like why screw around any longer?

However, if this is one of those do it because I can things here is one way I did it that had some promise:
To keep from opening the jaws on the chuck every time, make a case sleeve with a chamber reamer to fit the case and deep enough to expose the neck and shoulder junction and the case head to be in front of the chuck jaws, leaving a stub at the rear to hold in the chuck. Make a second sleeve with close tolerance fit to slip over the first. Split the first sleeve in half, just in front of where the chuck jaws grip the sleeve and even with the case head. You can now drop the case into the bottom half, replace the top, slip the second sleeve over the first and have enough grip to keep the case from spinning during trimming. Then, remove the outer sleeve, the top half of the inner sleeve and remove your brass. This was made out of aluminum but a chunk PVC or similar plastic would work just as well. Just don't use anything that's slippery or the brass case will revolve in the holder when the cutter touches the case.

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