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How do I drill Gelcoat without cracks

Old 08-26-2021, 03:40 PM
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Default How do I drill Gelcoat without cracks

Going to install 2 strap brackets for Bimini with #10 screws. Best I can figure final drill size is 5/32. What technique for drilling without cracks.

thanks
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Old 08-26-2021, 03:56 PM
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Originally Posted by PA.WOODCHUCK View Post
Going to install 2 strap brackets for Bimini with #10 screws. Best I can figure final drill size is 5/32. What technique for drilling without cracks.

thanks
Easiest methods Iíve found are donít use an extremely sharp bit, go in reverse to burn through the first layers, lightly counter sink the hole before you run the screw in. If you donít have a counter sink or are lazy to change your bit you can also use your phillips screw tip as a small counter sink haha
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Old 08-26-2021, 04:56 PM
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Originally Posted by lavey jr View Post
Easiest methods Iíve found are donít use an extremely sharp bit, go in reverse to burn through the first layers, lightly counter sink the hole before you run the screw in. If you donít have a counter sink or are lazy to change your bit you can also use your phillips screw tip as a small counter sink haha
Quoted for truth...THIS is the best way.
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Old 08-26-2021, 05:00 PM
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Originally Posted by lavey jr View Post
Easiest methods Iíve found are donít use an extremely sharp bit, go in reverse to burn through the first layers, lightly counter sink the hole before you run the screw in. If you donít have a counter sink or are lazy to change your bit you can also use your phillips screw tip as a small counter sink haha
X's 3
And use a very light touch !
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Old 08-26-2021, 05:01 PM
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Do not run the screw into the glass without an appropriate counter sink. Best done with a stone so as to not create any rough / sharp edges. Just want a smooth bevel, and do not over tighten the screw and pull the gell from the glass substrate.
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Old 08-26-2021, 05:03 PM
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Originally Posted by lavey jr View Post
Easiest methods Iíve found are donít use an extremely sharp bit, go in reverse to burn through the first layers, lightly counter sink the hole before you run the screw in. If you donít have a counter sink or are lazy to change your bit you can also use your phillips screw tip as a small counter sink haha
^^^^ This, plus one more hint based on years of experience. Normally, when sizing a hole for wood or something similar, one goes slightly smaller than the root diameter of the screw when sizing the drill bit. For fiberglass (topped with gelcoat), it's a bit different. Size the drill bit exactly for the root diameter or even a bit bigger. Although this theoretically reduces the strength of the hold down, it also prevents stress cracks.
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Old 08-26-2021, 07:58 PM
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i always put down masking tape on the fiberglass before drilling, reduces cracks/chunks.
remove after drilled.
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Old 08-26-2021, 08:52 PM
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Originally Posted by SabrToothSqrl View Post
i always put down masking tape on the fiberglass before drilling, reduces cracks/chunks.
remove after drilled.
I totally agree with this...A masking tape on the fiberglass before drilling does the trick.
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Old 08-26-2021, 08:56 PM
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Why dont you thru bolt it?
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Old 08-26-2021, 10:07 PM
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Masking tape and then counter sink
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