Are you referring to the tit on the back side of a spring?
The tit should be the diameter of the upper leaf of the spring. File it out square to start, then knock off the corners to make it octagonal. Measure the thickness of the tit, and drill a hole of that dimension into the end of a piece of round stock. With a hack saw, cut two, three or four cuts across the end about 1/16" deep. Determine the direction of rotation of the rod, and with a safe sided three corned file, create a little backdraft from one of the cuts up to the top of the next one to it. Continue until you have created a mill with teeth all around. Harden the rod - if high carbon, red heat, quench, temper to straw. If mild steel, case harden.
Be sure the spring is held securely in the drill press vise. Bring the cutter down on the tit and make it cylindrical. Easy peesey. I'll see if I have a picture of one, and if not, I'll take one, and post it here.
They are useful for making the tit on a fly/detent, too.
