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?

Router table Closeup of hole and screw

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    Are the holes in the table possibly counterbored for cap-head screws rather than countersunk for flathead screws? Or just increase the size of the countersink... – Ecnerwal Sep 8 '16 at 3:03
  • No, the holes in the router table are conical pits, not cylinders. – Chris Nelson Sep 8 '16 at 13:59
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    A larger diameter counter sink bit and or possibly one with a shallow taper. You do want the heads to be flush or slightly below the table top. not really that difficult. counter sink just a little at a time checking to see if the heads will sit flush. This can be done with a hand drill. – Ed Beal Sep 8 '16 at 15:16

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