Jig for doing popper mouths

[backcast]

Jigman, sorry to criticize without offering an alternative. I have not done popper mouths that way so I will have to think about it. What about placing a vertical pin in a board the same diameter as the through hole. Place the plug on the pin, then keep the plug from spinning with a handscrew clamp. The pin could be a long machine screw. You could add some blocks to elevate the clamp closer to the action. Some handscrew clamps have groves for grabbing round stuff. Some of the other posts look promising as well