Trimming Brass rims

[torker]

I've made this fixture for trimming the rims off of brass. The fixture works sometimes, and then not. There are times when a piece of brass will lift out of the fixture when the endmill touchs it. This does not happen all the time in any specific hole. It seems random at times. I've marked with a sharpe marker when this happens. But on the next batch it won't happen there but somewhere else.

Could this be because the fixture is aluminum? Not enough gripping power? The brass will spin like crazy in the fixture, and cause some chatter in the machine. I'm only taking a .030 off per pass. Would a steel fixture work better?

I'm using a lubricate also when performing this operation. Any ideas?

Thanks.

[Reload3006]

I have never tried machining the rims off like that. But doing or rather trying to gang mill other parts it usually doesn't work very well because of the differences in part size. in this case brass size unless you mike them and separate them all into groups that are the same size the larger ones will keep the vise jaws from gripping the smaller ones. Some time not often you can trick it into holding by wrapping paper or some other softer material around them and it will compress and hold the smaller parts. Unless they are held pretty tightly the endmill flutes will try to suck them up out of the fixture too. be very careful of the primers as when the end mill cuts through the primer pocket the primer may spin just like the brass also there is a steel anvil inside that the endmill may not like very well. You may find its a lot faster to do them one at a time. Pain in the rear I know but usually a lot more trouble free.

Also it may help if you mill about .010 off of each face of the fixture to give the vise a little gripping room it will not be a round hold when you put the vise jaws together. When making "Soft Jaws" like that i usually put a shim or spacer between the jaws when i drill the holes or mill a step in the vise so it can clamp better.

Steel will last longer but will not work any better.

[torker]

Thanks Reload, I knocked out the primers as suggested and using lub. I thought about using some type of material like electrical tape inside the holes, maybe some adhesion might help this out. Thanks again.

[Cap'n Morgan]

You need something to lock the cases in place and take up the slack from the small variation in case dimensions. It could be as simple as a hole drilled into the side of the pockets and a piece of rubber (perhaps cut from an o-ring) inserted in the holes. Adjust the length so the rubber will compress when the fixture is closed.

[dave391]

Have the cases all been put through a sizing die ? That should make them more uniform.

[GRUMPA]

torker if there is a way for you to use a lathe do it. You have absolutely no repeatability using that. Personally the way your doing it is inviting something bad to happen. A simple collet on a lathe and it would take you longer to put in the part than it would to trim it down.

[Crawdaddy]

X2 on the lathe. I use a cheap chinese made lathe and it works fine. You can either chuck the case or put it in a collet.

[arjacobson]

Instead of milling across take a center cutting end mill and plunge each pc. I do it this way on my bridgeport and can run them pretty fast using one vee in my vice jaw.

[Fritz D]

Are you trimming off the end of the case (where the headstamp is). If so, I'm curious why you need to do this?

[ReloaderFred]

They do it to use the case for a bullet jacket for swaging. It shortens the case to near what a factory cup and core bullet would be.

Hope this helps.

Fred

[Fritz D]

That clears it up . . . thanks for the reply.

[torker]

Thanks for the advice on this issue from all. I did the plunging operation and it seemed to work alot better. I put some electrical tape inside each pocket to try to get some adhesion. It works... Seems like alot of time, but that's about all I got right now. Can trim rims off, flip over and cut to lenght 40 pcs. in 18 mins. Using the plunging method.

Still thinking on a new fixture, any pics of other types of fixtures?

thanks again for all the advice guys...

[Bwana]

"Be very careful of the primers as when the end mill cuts through the primer pocket the primer may spin just like the brass also there is a steel anvil inside that the endmill may not like very well."


The anvil is brass not steel. The part about the primer possibly interfering with the cut crossed my mind also.

[Reload3006]

"Be very careful of the primers as when the end mill cuts through the primer pocket the primer may spin just like the brass also there is a steel anvil inside that the endmill may not like very well."


The anvil is brass not steel. The part about the primer possibly interfering with the cut crossed my mind also.

I happen to have several Winchester primers that the anvil is steel. Unless you know for sure you assume the worst. but even a chunk of brass caught by the flute of the end mill will tear it apart.

[MightyThor]

The fact that the primers are still present indicates that the brass has not been sized thus your not guaranteed a uniform diameter of the brass in your fixture. You could get a more uniform grab by sizing all of the brass before milling. If you want to leave the primers in place just pull out the decapping pin from your size die.

[gjemba]

I use the same method as shown here:

http://castboolits.gunloads.com/showthread.php?t=104778

My cases would spin sometimes also so I used a center punch to make a bunch of pock marks on the sides of each of the holes that hold the cases to provide a better grip. That helped.
Gary

[Danth]

You might try alittle rosin on each case.