Napkin Ring Bender Jig -

We use the jig style shown on the far right. Our version utilizes a 1-1/8" OD pipe and a 3/4" piece of round stock as the female/male socket.

Both the pictures and the Jig design are from the Vol. 8 #1 issue of ABANA's "Hammer's Blow" magazine. (I'd include the author too but I couldn't locate any reference to him/her in the origional article).