3 Attachment(s)
Jacket Blanking Die - Attempt to make my own jacket blanking die
I'd like to make my own jackets! I have the time and equipment (at least most equipment) and, having been inspired by others on this forum, am looking forward to (hopefully) blanking, cupping/drawing then finally swaging bullets with my own dies.
I've read Corbin's book, the NRA book, the old Ted Smith PDF. By way of background, I run a youtube channel documenting my home shop machining and prototyping endeavors, http://youtube.com/saunixcomp. I own a set of Corbin dies (typical setup of squirt die, core seat and point form) which have been a great reference and starting point.
I purchased some 1" copper strips from Corbin. First step is to make ~0.95" blanks (which can then be cupped and drawn). The two examples I drew on were Corbin http://www.corbins.com/jmk-1-h.htm and and KTN http://castboolits.gunloads.com/show...=1#post1139178. The end goal is a 124 grain JHP 9mm. (As an aside, the 9mm jackets that Corbin sells max out at ~115 grain; anything heavier needs a longer jacket).
My hope was to make something I can use in my existing Corbin press (which, as mentioned below, seems inadequate for blanking). Once I have blanks, I can start making cupping and drawing dies.
The punch is annealed 41L40. I turned it down on my Emco V13 lathe and then used a file, then lapping compound to get to a decent finish and accurate diameter. Punch OD is 0.946"
The die is an unknown grade of steel (only piece of ~1.5" I had on hand). I expect to have to make these out of tool steel in the future. The Die ID is 0.950" I was told by a tool & die guy that 0.004 total clearance (2thou around the circumference) was appropriate for this application.
(FYI, in the attached photos, the die isn't finished; an ramp/angle & window needs cut which will allow the cut-blanks to fall out of the die into a holding bin)
The punch/die worked OK on a piece of 5thou brass shim stock but cannot come close to shearing the ~0.031" copper.
The KTN jacket blanking die and Corbin both have a slot that the stock feeds through (convenient!) which also serves as a self-aligning sidewall for the punch/die. My punch/die align OK in the Corbin due to that press' design. However, I was thinking about putting my punch/die in a 12 ton shop-press (which surely has enough power to sheer) but I don't have a way of retaining the punch alignment...
How does KTN cut that narrow slot? With the cutting edge of the die recessed inside the die, how would you sharpen or grind it?
dies sets and punch clearance
Quote:
Originally Posted by
aaronraad
For punching the blanks, I would use a die set, possibly used. Search eBay for "danly die" or "kick press" to get some hits. The set will provide a way of keeping things aligned and easy to swap in and out.
The die clearance depends on the material and thickness. Too much clearance and it will smear instead of shearing. Too little and forces go up, etc... I think that Machinery's Handbook covers it. Get a copy if you don't have one since it covers the world of machines and metal working. .002 seems like a lot for this application off the top of my head.
I would lean toward using a spring loaded metal stripper plate but the rubber method might be good to try first.
You can also slightly cup the punch so that you are not shearing the entire circumference at once. This will lower the force needed a lot and maybe allow the use of a manual or small air press. You can add all kinds of other goodies like a feeder and a weed cutter to chop the scrap but those are not needed until you start getting good blanks.