Afternoon all

I need to drill an 8mm hole in the top of my scuttle. I don't want to dismantle dash/elecs etc to allow access to the reverse side.

So what is the best way to get a neat hole with no acess to the reverse side and not knacker up the gel coat?

I was thinking of
1. drill smallest hole possible and enlarge with needle file etc. take time but sfer bet?

2. use step drill but would I drill quick or slow speed?

or is there another way. All opinions welcome as with most things I'm clueless


Cheers all in advance for any assistance

masking tape the gel coat, drill through that at say 5mm, then open it out a bit with a file/dremmel thingy, but as below don't pull up through the gel coat with the file, only push down

[Edited on 30/3/10 by blakep82]

Slow as possible with a drill gets my vote and I'm currently drilling ALOT of holes in various bits of GRP!


I've tried every which way, files can chip the surrounding gelcoat, and pilot holes can cause the main drill bit to snag.

I'd be going for option 3 - Drill it with an 8mm drill bit...

2nd Steve's point of view. Masking tape to stop the bit wandering, then drill straight to 8mm. If the hole needs to be very accurately located, use a very small pilot hole first just to start the 8mm bit....

Definately go straight for the final size drill bit. Lots of masking tape, mark your centre with a scribe or bradawl to stop the bit wandering and drill nice and slow - let the bit do the work. I also find that a very slight wiggle of the drill once it's gone right through with the bit still spinning eases withdrawal of the bit once stationary and avoids pulling up at the gel coat.

Use a wood drill which will scribe the gel coat before the hole is cut - and VERY slowly. The lower one of these three
Rescued attachment mixed_wood.jpg

Hi

As per Mark's advice above ............. the normal term for this type of bit is 'Lip and Spur', also works very well in plastics, Lexan Perspex etc.

Regards Mick

Better to use a blunt drill bit and go slow IMO.

quote:

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Originally posted by Mark Allanson
Use a wood drill which will scribe the gel coat before the hole is cut - and VERY slowly. The lower one of these three

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quote:

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Originally posted by scootz
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cheers all for the advice, looks like I'm going for the 8mm drill bit straight out then.

My main worry was I'd normally put a block of wood behind where I'm drilling to stop the fibreglass ripping when the drill goes through. I take it as long as I don't push too hard and drill slow this shouldn't be a problem?

Keep an ear open for the screams as it wanders from one end of the scuttle to the other

quote:

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Originally posted by cd.thomson
Have you seen kick-ass scootz, or do you have a thing for girls dressed as superheros

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If you don't have a blunt drill (which might happen, as sod's law states all your drills are blunt except when you need them to be...) set the drill to reverse to lower the risk of the drill "catching" on the gelcoat and making a right mess of your scuttle.

quote:

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Originally posted by blakep82
masking tape the gel coat, drill through that at say 5mm, then open it out a bit with a file/dremmel thingy, but as below don't pull up through the gel coat with the file, only push down

[Edited on 30/3/10 by blakep82]

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drill 8 mm hole in block of wood hen fix to scuttle - should preven wandering.

then 8 mm bit, sharp and slow.

quote:

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Originally posted by sebastiaan
If you don't have a blunt drill (which might happen, as sod's law states all your drills are blunt except when you need them to be...) set the drill to reverse to lower the risk of the drill "catching" on the gelcoat and making a right mess of your scuttle.

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I always drill a smaller hole eg 5mm and then open the hole up with a tapered reamer to the desired size. Perfect edges every time and only takes a minute to do.

Always, always drill to the final size straight off otherwise you will chip the gel coat.

Mark the centre on some masking tape, make sure the drill is sharp then drill your hole as you normally would, I find low pressure and moderate speed to be good. If you find the drill wanders, use a smaller drill to create a dimple, not a hole, for the centre of the correct sized drill to pick up on.

Much easier to control for this particular job (though I wouldn't want to go drilling steel using one )

hand drill or drill in reverse always worked well for me.

infact, drill in reverse is probably the optimum. if you can chip the gel doing that, you deserve a medal for being clumsy
tom

so....how did it go then....?

No damage I hope

Let's see the finished result

I didn't realise that this thread had continued in my abscence. The hole was fine thanks to all the sagely advice I received here before drilling.

Next up 4 12mm holes in my nose cone!! even though the 8mm went fine I'm still dreading doing 4 12mm holes.

Nick surely you don't want me to post a photo of an 8mm hole? it wasn't for any particularly intersting reason.

Thanks again all for the help.