Re-sizing a Star sizing die

[wv109323]

I have a factory bullet sizing die that is marked .358. The actual diameter of sized bullets is .3573 to .3577 depending on alloy.
I want to take the diameter up to an actual .358. I will be using a drill and a flap wheel.( sandpaper wrapped around a rod)
What grit sandpaper should I start with and finish with?

[VHoward]

Are you using a quality accurate caliper to measure the diameter of the bullets? Or the cheap Chinese knockoffs you get from Harbor Freight? Most digital calipers will have an error rate stated on them as +/- a certain value. Your measuring .0003 to .0007 " too small and that could be within the error rate for those calipers.

[wv109323]

I am using a quality micrometer. (Brand name escapes me right now). I was wanting to get the full .358 . I have a .357 die and it is right at .3570 so I wanted to increase the difference and have a true .358 for my .357 revolvers.
I did not want to start with a coarse paper and remove too much material and have a .359 die by the time I polished it out.

[Mal Paso]

600 grit wet or dry emery or garnet paper is where I'd start. 400 if you need faster but I doubt it. That's not much material. Any small scratches will be 90 degrees to the boolit path so I wouldn't worry about finishing with a higher grit.

I used 320 diamond paste and an expanded piece of thin wall brass tube from the hobby shop to open a carbide sizing die a few thousandths and I just twisted it with my fingers. A drill would have been too much. Flap wheel will be slower but it's easy to go too far.

Absolutely right on most Digital Calipers. Ignore the last digit, it's just not capable of resolving ten-thousandths. The Harbor Freight Micrometers however are a good value. I have checked mine against Standards and they are spot on closed in the middle and max. They resolve thousandths but it's pretty easy to see that my pin gauges are .0002" under the stamped size. Being able to see a difference of .0002" is usually close enough for boolits.

[masscaster]

Run a boolit through the die, then use a lapping compound and the sized boolit(s) to hone it out.
It's the same process as lapping a mould. Since your not taking much metal this would be easier.
I've done it with RCBS, Lyman, and Star Dies when only needing .0005 - .001 larger.

Jeff

[Hang Fire]

Most bullet sizing dies I have found to not be hard at all. I have opened several up, some from .257" to 8mm.

I recently opened up a .284" die to .302" for 7.35x51 Carcano. A bud who is also a M38 7.35x51 shooter, went ga-ga over it, so gave it to him. I then made my own .302" lubri/sizer die, it was not difficult using a cheap Chinese mini lathe and mill. Do not sell these mini machine tools short, with correct adjustment and within limitations, they are capable of precision work. Rather than use band width here, click URL and then scroll to bottom as to how it was done.

http://hstrial-rchambers.homestead.com/Rolands_Mini_machine_shop.html

[rbuck351]

Yep, I have one of the chinese 7x14 lathes (converted from a 7x10) and I have made a bunch of sizer dies for my Lyman, RCBS and Star luber sizers. I also have made top punches, dies for a Swag-o-matic, gas check makers and a bunch of other special tools for the loading bench. Once you have properly aligned the lathe, it works very well for the small projects for the reloading bench. I retire in about 6 months and will be getting a bigger lathe and a mill but for now the mini lathe does well on the small projects.

[wv109323]

I thought I would update the thread for any one in the future. I started with a flap wheel mounted n a drill press using 400 grit paper. The flap wheel was a 3/16 wooden dowel with a slot cut on end end to insert the sandpaper.
To make it short the 400 grit paper would not remove any material. A total of 12-15 minutes of sanding resulted in no material removed. Of course I stopped around 15 times to measure my progress.
I then went to 100 grit paper. Even with 100 grit it took at least 5-7 minutes of sanding to remove the material I wanted. I ended up with a die that will size at .3582". I polished it with the 400 paper.
This took a lot more time than I thought. I was also concerned about removing too much material but the Star die was tough. I don't know about other makes but I spent a lot of time to remove .0005".