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ContinuousWave: Whaler Repairs/Mods
Drilling Holes Through Gelcoat - Without Chipping
|Author||Topic: Drilling Holes Through Gelcoat - Without Chipping|
posted 03-27-2002 01:09 PM ET (US)
I was installing some hardware today and didn't want the chipping that usually occures around the drill site. I ran across some old plexiglass drill bits, one of which was slightly larger than the O.D. of the screws I was using. I used the plexiglass bit to drill through the gelcoat and berly dimple the fiberglass. then I used a smaller standard bit to drill my hole through the glass. Results were a perfect pilot hole for the screw with none of the usual chipping or seperation. I even removed the screw and the hole was perfect, didn't look like a mini volcano . I hope this helps.
posted 03-27-2002 06:14 PM ET (US)
Buy a dremel machine at Home depot with 142 tools in the case all for $99. It's fantastic for working on boats and fiberglass.
posted 03-27-2002 06:52 PM ET (US)
I agree tabasco, the Dremel is the kind. I purchased a tungsten carbide bit for some pre-patch grinding.
What other bits or attachments have you found to be most useful for your Whaler work? I am a bit overwhelmed by the set.
posted 03-27-2002 06:52 PM ET (US)
I use forstner bits to cut first through the gelcoat. They also work great.
posted 03-27-2002 07:01 PM ET (US)
Your post was timed perfectly, I just about do some drilling and was wondering how to best avoid gel damage. Pardon my ignorance, but what is a "Plexiglass" drill bit ?
posted 03-27-2002 10:54 PM ET (US)
The "plexiglass bits" I was reffering to are made to drill plexiglass they have a long ground tip. The ground tip is about 2-3 times longer (very pointed looking) than a standard bit, I bought them at TAP Plactics but any store that sells plexiglass should stock them. Guys I guess I didn't make myself clear, this is for drilling small screw holes.
"Arch A", I bet you don't have a 9/64" Forester bit.
And "tabasco" my wife has one of those $99 Home Depot Dremel's but I wasnt trying to hog out a hole in the dash for a new gauge, just a nice sanatery screw hole, and I got it
posted 03-28-2002 12:43 AM ET (US)
The most useful Dremel bit is the one you
don't have. Don't be shy about buying more.
And leaf through the catalog and look at the
display in the HW store now and then (it's
good for the soul, esp. you folks that have
a winter ;-) to prime your brain with ideas.
I've used mine to buff out the anchor light
posted 03-28-2002 08:11 AM ET (US)
While we are an the subject of tools. My wife bought me a Roto-Zip for Christmas. I love it. I haven't tried it on the boat yet, but I bet it will chip a lot less than a saber saw for some of the cuts I need to make in the console.
posted 03-28-2002 10:46 AM ET (US)
Don't be so sure. I just used one for the first time whilst sheetrocking at a buddies house. They have a mind of their own and, at least in sheetrock, they don't want to go in a straight line. Be careful. brace your elbows against your boby and your hands against the work piece.
I wolud suggest scoreing the outline of your cut out with a razor knife then stay just inside the score line. Should prevent chipping.
posted 03-28-2002 11:59 AM ET (US)
Boy, I'm glad I'm not the only one that can't cut a streight line with a Roto-Zip. It's a good tool for some situations but it's not the "do-all" tool that they would lead you to be and sheetrock just eats up the bits.
And "triblet" your right-on about the Dremel bits and there are times it would be handy but I seldom think about using it.
posted 03-28-2002 12:22 PM ET (US)
I know we're a little off topic, but ditto on the Roto-Zip. I just used mine to cut holes for steering and gauges on my new custom console (1" mahogany) and it really can get away from you. However, I stayed within the lines and with just a little cleanup with a file the holes look great.
Back on topic, I have found that if you carefully tape over the area to be drilled (then obviously mark the area to be drilled on the tape), this should greatly reduce chipping. However, there is no substitute for the right tool; the Plexiglas drill bit is the way to go.
posted 03-28-2002 09:32 PM ET (US)
There is no need for specialty bits or tools (although I like to use brad point bits nearly exclusively).
Simply put a piece of masking tape over the area to be cut or bored.
Works every time.
|Tom W Clark||
posted 03-28-2002 10:53 PM ET (US)
A few random comments:
The easiest way to get a perfect, chip free hole in gelcoat is to use a Forstner bit. Brad point bits are great too but I regularly bust them up in my line of work. Masking tape is good most of the time.
"Rotozip" tools and the other like tools are great with drywall which is what they were originally designed for. They can be a handful and are best left to the pros. I really don't recommend using them on your boat or for "drilling holes".
They can be handy for cutting irregularly shaped cutouts, but if its fiberglass, use a real router and a real bit. (Rotozip tolls, and Dremel tools are nothing but light weight routers)
Dremel has it figured out. I have to confess that I own a Dremel and it is great in special situations, but they got you when you think they don't cost much. As Chuck says, the most useful Dremel bit is the one you don't have. By the time you get all the bits you need and those that need replacing, your into it for hundreds of dollars. What a racket.
posted 03-29-2002 09:16 AM ET (US)
There are easier ways to prevent chips. One way is to set the drill in the reverse rotation until the gelcoat is clear (that's the lazy way). The best way is use a counter sink bit on high speed with a light but steady touch. I have used both methods during my years of rigging and restoring boats in college.
By the way, The reverse rotation method is best when using a hole saw on all surfaces including vinyl-faced bolsters and cabin interior pieces.
posted 03-29-2002 01:57 PM ET (US)
Great tips, I'll file those away for future use.
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