POTD was making another punch/die for a project in reproducing old Erector set part number ‘NU’ parachute jumpers. The parachutes have paper washers on either side of the chute material with a brass eyelet holding them together. I made a 5/8” punch with a less aggressive center “prick” a few days ago, this punch/die were for finishing off one style of the disks made from the 5/8” punch. In this case I needed a 3/16” diameter punch. Had 11/64” and 7/32”, but alas, no 3/16” . . .
My Roper Whitney #218 punch press uses 1 ¼”, 2 1/8” or 2 ¾” dies, and punches either ½” or 1” diameter. Made the die first. Started with a slightly over 1.25” diameter O-1 round, turned down to 1.25”. Then bored out the round to depth/diameter which is at the bottom of the die. Cut off the round on a band saw and back to the lathe. Faced, center drilled and drilled/reamed to a 3/16” hole. I was shooting for about 0.005” clearance between the punch and die, so then ran a #11 drill bit (0.191” diameter) through the reamed hole. It was only scraping 0.002” on the radius so figured it’d be pretty close to the correct diameter.
Did the punch from a piece of ½” drill rod. Simple turning job to 0.1875” diameter (3/16”). The shank got a relief area for an anti-rotation screw in the press punch receiver. Parted and cleaned up the nib with a table top belt sander.
Hardened the punch & die with an oxyacetylene torch, then tempered to ~460 F on a Thermolyne hot plate.
If you are interested in what I’m doing with the 3/16” punch, hit the link below for the ‘NU’ parachute jumper thread.
http://hobby-machinist.com/threads/erector-set-part-number-nu-parachute-men-punch-and-die.59615/
Bruce
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