On Saturday, September 21, 2013 4:24:20 PM UTC-6, Pete C. wrote:
Karl Townsend wrote: I plan to use a press brake bottom die as a "V" block. Then two barrels clamped and held straight. Top one is just scrap for a guide. bottom of top barrel bored out just a bit to hold the button.. Put button in bottom of top barrel and the long HSS push rod. Clamp it all together in line. Press a bit, retract, put in short piece of HSS - maybe 4", press a bit, put in another HSS stick, repeat. Karl How will you ensure the button rotates at the proper twist rate? I know it should self rotate, but with all that force pressing on the back there had better be some good lube to let it turn.

The book I've got on setting up for button rifling had the button ground for the proper lead, it was PULLED, not pushed, and the rod that it was attached to had a thrust bearing at the ram end so the works rotated at the button's lead rate. A universal cutter grinder with diamond wheels was used for making the buttons, then the button was polished afterwards with finer and finer grades of diamond lapping compound. If the joint to the pulling rod broke halfway through the barrel, the barrel blank got bandsawed apart to recover the button.

If I were to go into the barrel supplying business, it might be worth my time to create all the gubbins to do button rifling. A sine-bar machine is a whole lot more flexible as far as what twist rates can be done on it, leaves a lot less stress in the barrel, but is a whole lot slower. For my barrel needs, it's just a lot cheaper and easier to buy a premium blank from a name outfit that already has the skill than to make one on my own, satisfying though that might be. These days, I only machine up what I can't buy. Life's just not long enough to make everything from scratch.

Stan