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#11
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Re: Drill Bit / screw sizes
You are fine drilling one or two sizes smaller then the screw, but you MUST counter sink the hole to stop spider cracking!!!
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1986 V20  Old Fishermen never die, we just SMELL that way!! 
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#12
03-16-2007, 03:02 PM
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Re: Drill Bit / screw sizes
You are fine drilling one or two sizes smaller then the screw, but you MUST counter sink the hole to stop spider cracking!!!
__________________
1986 V20 Old Fishermen never die, we just SMELL that way!!
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#13
03-17-2007, 05:41 PM
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Re: Drill Bit / screw sizes
I take the screw and hold a bit up to it...if I can see "a little bit of the edge of the threads" stickin' out wider than the bit-shank, that's the one ... and use a cone-shaped bit or counter-sink edge of hole like MJ says above...fiberglass does not take screws like wood does... ;) ...
__________________
'74 V-20/ BF 150 '95 V-21/ BF 150 '84 V-20/ 200 2.4 Merc '87 V-20/'18 F150 Yamaha 
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#14
03-17-2007, 05:41 PM
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Re: Drill Bit / screw sizes
I take the screw and hold a bit up to it...if I can see "a little bit of the edge of the threads" stickin' out wider than the bit-shank, that's the one ... and use a cone-shaped bit or counter-sink edge of hole like MJ says above...fiberglass does not take screws like wood does... ;) ...
__________________
'74 V-20/ BF 150 '95 V-21/ BF 150 '84 V-20/ 200 2.4 Merc '87 V-20/'18 F150 Yamaha
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#15
03-17-2007, 08:21 PM
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Re: Drill Bit / screw sizes
Thanks To All Who responded,
Thought for sure there was a fiberglass screw/drill bit chart. There should be one. Have seen to many people crack their fiberglass by forcing a screw. Appears that a 1/32 to 3/64 of an inch less than the thread diamater will be about the right size pilot hole. Always remember to put petroleum jelly on the screw threads.
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#16
03-17-2007, 08:21 PM
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Re: Drill Bit / screw sizes
Thanks To All Who responded,
Thought for sure there was a fiberglass screw/drill bit chart. There should be one. Have seen to many people crack their fiberglass by forcing a screw. Appears that a 1/32 to 3/64 of an inch less than the thread diamater will be about the right size pilot hole. Always remember to put petroleum jelly on the screw threads.
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#17
03-17-2007, 08:30 PM
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Re: Drill Bit / screw sizes
The petroleum-jelly sounded good at first...but most screws that go in boats should be coated w/ marine grade silicone... or at least that's the way I do it ...nothin' works for everybody ;) ...
screw-threads in fiberglass...it doesn't take much BITE to get a good, firm hold :D ...
__________________
'74 V-20/ BF 150 '95 V-21/ BF 150 '84 V-20/ 200 2.4 Merc '87 V-20/'18 F150 Yamaha
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#18
03-17-2007, 08:30 PM
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Re: Drill Bit / screw sizes
The petroleum-jelly sounded good at first...but most screws that go in boats should be coated w/ marine grade silicone... or at least that's the way I do it ...nothin' works for everybody ;) ...
screw-threads in fiberglass...it doesn't take much BITE to get a good, firm hold :D ...
__________________
'74 V-20/ BF 150 '95 V-21/ BF 150 '84 V-20/ 200 2.4 Merc '87 V-20/'18 F150 Yamaha
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#19
03-17-2007, 10:24 PM
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Re: Drill Bit / screw sizes
I kept dropping my countersink bit in the water, in a pinch, i took the screwdriver bit and used it to bevel the hole before I ran the screw in, worked pretty good
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#20
03-17-2007, 10:24 PM
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Re: Drill Bit / screw sizes
I kept dropping my countersink bit in the water, in a pinch, i took the screwdriver bit and used it to bevel the hole before I ran the screw in, worked pretty good
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