drilling small pilot holes on deck

[bcarli]

No stupid questions...right?
I need to drill some small pilot holes so I can screw some deck fittings in. I remember doing this before with regular wood drill bits and it broke away some of the surrounding gel-coat. So I'm now thinking of using metal bits and drilling at a very slow speed.?????
don't want to repeat the last time...any ideas

thanks
ps what would you use as a sealer, boat life, silicone..4200 ?

 

[psneeld]

One technique to not chip the gel coat is to go through it with the drill in reverse.

Use a slightly larger bit than what you plan on drilling deep with.

 

[Bacchus]

Start with small pilot hole then counter sink bit before drilling larger. A counter sink / chamfer not only prevents chipping but provides a "well" for sealant around any fasteners.
I'm a fan of butyl tape for any bedding.

 

[C lectric]

To me a high speed for a small drill bit would reduce the chance of chipping. THe smaller the drill bit the higher the speed should be so each rotation takes a smaller bite and use low pressure.
Bit must be sharp.

And yes to the countersinking.

 

[Comodave]

I just use regular bits and drill the holes, then use a countersink to chamfer the edges of the hole. Countersink it slightly larger than the threads of the screw so you don’t lift the gel coat. This prevents the gel coat from chipping and also provides an area for whatever sealant you use to form sorta an O ring around the screw so it won’t leak.

 

[jleonard]

Put blue painter's tape on the location first, then mark and drill the hole using the reverse direction method.

 

[Flatswing]

No stupid questions...right?
I need to drill some small pilot holes so I can screw some deck fittings in. I remember doing this before with regular wood drill bits and it broke away some of the surrounding gel-coat. So I'm now thinking of using metal bits and drilling at a very slow speed.?????
don't want to repeat the last time...any ideas

thanks
ps what would you use as a sealer, boat life, silicone..4200 ?

A sharp bit won’t chip. Definitely countersink, I’m also a big fan of butyl (befit tape being my go to) but any sealant other than 5200 works. The commonest cause of chipping gel coat is too small a hole for the screw. If you can’t turn the screw in by hand, keep going up by 1/64” till u can. BTW if your deck is cored, best practice is to overdrill the surface hole, remove core with a keyhole bill in a Dremel or drill. Fill completely with thickened epoxy. Next day, drill, countersink & insert screw by hand with sealant. See Marinehowto.com for details per Mainesail.