Drilling fiberglass can be a time-consuming procedure if you wish to drill a perfect hole. The problem with drilling through fiberglass is that the drill bit has a tendency to chip the edges of the hole. This is because fiberglass has a gel-coated surface, and the edges of a drill bit tend to get underneath this surface and then chip it off. The larger the drill bit, the greater the likelihood of chipping. With a little time and patience it is possible, however, to drill a perfect chip-free hole in almost any piece of fiberglass.
Make an indentation with an ice pick or other suitably sharp object in the exact location where you want to drill your hole. This indentation prevents your drill bit from wandering and potentially scratching the surface of your fiberglass as you start your drilling.
Drill a small pilot hole in your fiberglass. Make it smaller than the finished hole you are planning to drill. Use a slow speed when drilling to reduce chipping, and do not put any pressure on the drill bit—allow the bit itself to do the work.
Drill a chamfer-edged hole in your fiberglass the size you wish your final hole to be. The chamfer should have an edge-slope of approximately 1/16 of an inch. Run your chamfer bit at a slow speed and, again, put no pressure on the bit. Allow the bit itself to cut into the surface of the fiberglass slowly and gently.
Drill your final hole using a sharp, clean drill bit. Again, drill on slow speed and do not put any pressure on the drill bit. Be careful to hold your drill perfectly perpendicular to your fiberglass surface so that your bit is cutting exactly at the edges of the chamfer. Take your time and allow your bit to do all of the work.
Take the time to do it right. Although it may seem like a lit of work, if you wish to drill a perfectly clean hole in fiberglass every time, this is the way you'll want to do it.