Best way to make coin blanks??

A lot of brass sheet is H02 hard. I am guessing it's to appeal to its multipurpose nature, the same sheet can be used for engraving, structural parts, whatever. I think if you plan on stamping coins, whether stamping a relief like the one pictured or stamping a full blown heads and tails coin, you would want to be sure to get soft annealed brass. The difference in deformation between the two covers a 300% range. You never know what you're gonna get with uncertified brass.
 
BGhanson did a good job covering the basics. The die set or shoe is important because of the leader pins to keep everything aligned. If the punch and die come out of alignment the punch and die will shear and ruin both. Also there hast to be the right amount of clearance between the punch and the die depending on the thickness of the stock you are blanking out. A good book on die design should be able to lay out some guide lines. Normally dies and punches are hardened and ground. For a limited run you might get by with just turning them and hardening after turning. I would use an air hardening steel like a2 because it isn’t quenched to harden it. That type of steel will hold dimensions with out warping as bad as carbon steel. The example you showed was a planchette that had been coined after blanking out. Coining takes a heavy tonnage press. The finish on the blanks is usually dependent on the original stock finish. Lastly hand feeding a punch press is dangerous. Have something that will keep the stock in place while the press comes down. Not your hand. Have both hands clear when the press is coming down. Good luck. Make sure and show us you progress. We like pictures.
 
Since even the Romans made coins 2000 years ago without any kind of modern machinery it should be very doable today.
Pierre
 
For punch/die clearance, here's a chart from the web (fabricatingandmetalworking.com). Your hole will be the size of the punch, not the die. The slug will be very close to the diameter of the die. I made a 0.650" punch/ 0.657" die for knocking holes in 0.036" CRS. The holes were 0.650", the slugs were 0.655" though they are slightly "cymbal" shaped because of the prick in the punch. If I flattened them, they'd grow a bit. Obviously not a concern for your project!

My punch/die were intended for 0.036" steel. The formula for calculating die hole size is:

Die hole diameter = Punch diameter + (material thickness x clearance factor)

In my case, Die hole diameter = 0.650" + (0.036" x 15%) = 0.6554"

I went to the higher side as I planned on punching some stainless also; I went with 0.657". The harder the material, the bigger the clearance. Also, the lower the clearance, the higher the pressure needed to punch. The larger the clearance, the bigger the burr.


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Another option for you since you want to make slugs, not holes, is an annular cutter. They do a nice job and give you a pretty clean cut.

Bruce

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Example of a perfect deal out there if you are looking to really go all in...

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