mounting a winch

[oddjobbob]

As I recall when I mounted the winches on my masts when I rigged my ketch in 2006 I had flat pads (bases) on oval masts. The winches "sat" flat on the bases and I drilled and tapped straight into the pads. If you don't make the holes perpendicular to the winch base the flat head screws you use won't seat into their "detent." (I know there is a better word for what I am calling detent, just can't think of it now.) If those flat headed screws don't seat flat as they are supposed to do they may interfere with the winch spinning. It sounds like your bases are cast so you have a flat pad for the winch to sit on. Drill the holes perpendicular to the pad, not the mast, unless by mast you mean the pad. And drill them all the way through the mast. When I sized the screw length I used an allen wrench that I had cut off so the "L" shape was very short. I slipped it into the hole to measure the minimum screw length and added used the next length longer. I didn't want a lot excess screw length in the mast to foul wires, even though in the case of my wiring everything was in conduits screwed to the interior of the mast. The main thing is to keep those screw heads flat or you will have to re-drill and tap (very hard) or grind then off later (not a good idea when you need to remove the screws later for some reason).
BRM3, just noticed your location. I rigged my boat there at the Ala Wai. That was before they tore down the store that was located by the bridge over the canal. Aloha!