I actually designed a router jig to trim either mushroomed or oversized tips to the correct diameter. It's based upon a flush trimming bit mounted into a Porter-Cable 690 router. The flush trimming bit is 1/2" in diameter and has a precisely sized ball bearing on the end of it. I built and sold one of these to Jimmy Mario back in Pittsburgh 35 years ago and then build one for myself. The router is mounted horizontally to the jig (The jig looks like a horizontal router table - the kind that is used to make mortise and tendon joints) with the laminate trimming bit sticking out of the front of the vertical member the shaft rests upon a stop and the ferrule goes up against the ball bearing. Anything that hangs over, Mushroomed or oversized tip, gets removed instantly as the shaft is rotated. The beauty of the tool is that Jim could buy 14mm tips and put them on all of his house cues whatever their tip size and within seconds they would be perfectly trimmed. If the oversized tip was a little off it didn't matter. Whatever extended over the ferrule was removed within seconds by a 1 1/2HP router spinning at 25,000 rpm. We could retip 50 house cues in 30 minutes using either superglue or 5 minute epoxy. I showed Tweeten Fibre my design but they where not interested in producing it commercially probably due to the cost of the router.
I still have mine and used it until I stopped playing pool five years ago. Works great.
