Re: Do I have to predrill before running screws into fiberglass
Originally Posted by paul323
If you drill through gelcoat - perhaps not in your case - start off by drilling in reverse. Reduces the likelihood of chipping.
This is a good tip. After drilling the small hole in the glass use a non-pilot bit whose size is about the size of your chamfer and - with your drill in reverse - start the chamfer by smoothing the edge of the hole before using the countersink/chamfer bit. If your large bit has the appropriate face angle you may be able to complete the chamfers with the bit eliminating the use of the chamfer bit (and higher potential for chipping the gel coat).
"It's not what you know that's important...it's what you do with what you know." -H.G. Rickover