[HELP] Machining Question

[Highpower]

(05-09-2020, 11:56 AM)Don Wrote: Primer is .317/.318 O.D so this would result in proper press fit, I believe.

Don

So you are reaming out belted rifle cases to stuff .50BMG primers into them? Is that it? 

[Don]

Tom,
Using an R-8 collet to hold the 3/8" shank 1/4" & 5/16" end mills. No, hadn't thought to check the T.I.R. of the end mill. I will do that next time I'm in the shop. I have a .0005 grad. dial indicator that should do the trick. Thanks for the idea. What did my Mom used to say? "2 heads are better than one, even if one's a cabbage head" She said some other stuff, but probably can't post it here. 

Happy Mother's Day to all.
Don

[Don]

Willie,
These are actually 20mm cases. The fired brass my Son bought are currently primed with the 20mm factory burden primers which have the anvil as part of the case. I'm attempting to make a proper dia. X depth pocket to use the .50 BMG Boxer primers which is what most reloaders do. If our information is correct, a dia. of .3125/.3135 with the primer O.D of .317/.318 "should" result in a sufficient press fit to retain the pressure of the ignition without backing the primer out. That's about twice the diametrical difference of a large rifle primer in a case such as a 30-06 or .458 Winchester. As I mentioned before. Reaming would be ideal were not for the large cham. on the leading edge of the reamer not producing a sq. corner at the bottom of the pocket.
Thank you for your interest. Always like to hear different thoughts, as they sometimes are staring you in the face and it doesn't dawn on you.
Don

[awemawson]

Why can you not modify the end of a reamer grinding it flat, or alternatively make a ‘D bit’ From a bit of silver steel (drill rod US speak) turned to your desired diameter and filed to the D form ?

[Don]

(05-11-2020, 02:00 AM)awemawson Wrote: Why can you not modify the end of a reamer grinding it flat, or alternatively make a ‘D bit’ From a bit of silver steel (drill rod US speak) turned to your desired diameter and filed to the D form ?

Andrew,
Both good ideas. Will keep them in mind. Thanks. Just took a few minutes out in my cold shop to check the 5/16" 4 flute end mill I used and the new one I will use on the next mock-up. Checked T.I.R. of shank w/n 1/4" of collet and it was .0000. Checked 4 flutes approx. 1/8" from end. Zeroed one - found 2 measured -.002 and 4th one measured -.0035. Sounds like a worn end mill, as expected. Installed new (unused) one in collet and it read .0000 on shank. Moved down to flutes as before and it read less than .0005 total variation for all 4 flutes. So. If my fixture mods. minimize vibration and the new cutter using WD-40 for cutting fluid all work, as suggested by the great guys on the forum, maybe the old, short, fat guy can make 60 good ones. Plan to run a couple more mock-up pcs. this weekend. Will let you know how I make out. Thanks again for everyone's help & suggestions.
Don

[Highpower]

(05-10-2020, 11:48 PM)Don Wrote: Willie,
These are actually 20mm cases. The fired brass my Son bought are currently primed with the 20mm factory burden primers which have the anvil as part of the case. I'm attempting to make a proper dia. X depth pocket to use the .50 BMG Boxer primers which is what most reloaders do. If our information is correct, a dia. of .3125/.3135 with the primer O.D of .317/.318 "should" result in a sufficient press fit to retain the pressure of the ignition without backing the primer out. That's about twice the diametrical difference of a large rifle primer in a case such as a 30-06 or .458 Winchester. As I mentioned before. Reaming would be ideal were not for the large cham. on the leading edge of the reamer not producing a sq. corner at the bottom of the pocket.
Thank you for your interest. Always like to hear different thoughts, as they sometimes are staring you in the face and it doesn't dawn on you.
Don

Oh, OK. The case didn't look to be that big in your pictures. Have you by chance tried using one of of these carbide cutters? Might make quick work of removing that Berdan anvil as well. https://www.midwayusa.com/product/1012926787

[Don]

Willie,
Thanks again for another idea. Have you used one of these? Here again, I see why this "may not work" on my cases. And, again. I may not be looking at it properly. I'm actually machining the 20mm primer out and wanting to wind up with a primer pocket of .3125. Not sure how that could be accomplished with the neat tool you found. Please understand, there is no way to use a primer removal tool to punch the factory 20mm primer out. No centered hole in the primer pocket which goes into the case interior because of the boxer primer. There are 2 smaller holes on either side of the anvil. This falls into the nothing that's hard is ever easy, I think.
Thanks again,
Don

[Highpower]

I have similar primer pocket "uniforming" cutters for small and large primer sizes. They are sized to closely fit the primer pocket. They cut a nice flat bottom with sharp corners to a uniform depth. I used to shoot a lot of Lake City brass which varied a bit in primer pocket "quality". The pockets are formed by a punch process which works, but isn't exactly what you would call precision machining. Many of them have a slight radius in the corners of the pockets from the punches and so the primer cups don't seat completely to the bottom flat. However I have not ever tried to use them to bore an oversize primer pocket in a standard brass case before and certainly not with a spent primer in place. Just spitballing an idea here.

Regarding decapping Berdan cases - you can either use a small sharp punch and a hammer to pierce the primer cup and pry it out - or use a hand tool made specifically for the task https://www.amazon.com/RCBS-9525-Berdan-...B0002INRT6

The cheap (but messy) way to remove them is to get a round piece of bar that closely fits the inside of the case mouth. Drill a hole in a block of wood slightly larger than primer pocket. Set the case on the block of wood with the primer over the hole. Fill the case completely with water. Insert the rod into the case mouth and give it a good whack with a hammer. Primer exits the case...  

[Don]

Willie,
Thanks for another good idea. I'm an old fart trying to avoid COVID-19 and you come up with a way I can get a severe cold and/or pee-numonia while I'm exercising the laws of hydraulics and probably beating my thumbs flat on top of the lung disorders. Geese. I know we just met, but you can't not like me that much already!!! Again. Cool idea, but if the whole 20mm primer was pushed out of the primer pocket, I'd have to make thin wall sleeves to decrease the O.D. of the 20mm primer pocket to accommodate the .317/.318 dia. of the .50BMG primers that I have. I'm going to try a similar trick to salvage the 2 O/S cases I have here, but doing 60 or more that way would be a real pain. Thanks again for a fresh idea. I'm just not sure that's the fix.
Later man. 
Don

[Highpower]

Well best of luck working it out. I just took delivery of a greenhouse kit that's going to keep me busy for awhile..