Some time ago, I bought a second-hand table saw. The original owner had extended the table with a section where he mounted a router. The holes are in the pattern of a Group C router and I recently bought a Porter-Cable 7518 which should fit. The holes line up but the screws holding the sub-base on the router base are 5/16"-18 and have a head about a 1/2" across. The countersink holes in the table are much smaller. Are 5/16" machine screws available with smaller heads? It doesn't seem that a reducer (a 5/16"-18 outside thread and something smaller inside) would work well here, if such a thing is even available. I could get smaller machine screws which would fit inside the threads in the base and then put a nut below but that would certainly make mounting and unmounting a chore. I could get a larger countersink bit and make the holes fit the larger heads but that seems hard to get right. Any thoughts?