Drill a chamfer edged hole in your fiberglass the size you wish your final hole to be. Chipping from the drill bit itself gelcoat chips away during screwing.
How To Drill Fiberglass Drill How To Get Surface
How to drill into fiberglass. The method i use which works about 999 of the time is to put the drill in reverse drill through the gelcoat then put the drill in forward and drill through the rest of the laminate. If you go in to the fiberglass with a regular twist drill a number of things can happen. Either using your hand or if you have clearance the drill running in reverse lightly score the fiberglass inside the bilge by applying pressure rotating the hole saw bit. The chamfer should have an edge slope of approximately 116 of an inch. Hold the center 14 inch drill bit of the hole saw perpendicular to the shower wall over the previously drilled pilot holes. Start the drill and gently push forward allowing the drill bit to cut into the material.
Allow the bit itself to cut into the surface of the fiberglass slowly and gently. Increase the rotational speed of the bit. If you simply attempt to drill a hole into the fiberglass you will have extreme difficulty in drilling holes without cracking the gelcoat. Keep an even forward pressure when the hole saw engages the fiberglass surface. Begin drilling on the slowest speed possible until the drill begins to bite into the fiberglass. Step 3 put on safety glasses and drill pilot holes on the marks that are half the size of the final holes using an electric drill.
To do this start from inside the bilge compartment and insert the hole saw bit into the hole you drilled in the previous step. Run your chamfer bit at a slow speed and again put no pressure on the bit. Put the point of a large nail on the marks and tap it with a hammer forming an indent in the fiberglass. 5 when the brad point penetrates the surface on the bottom. Do this to every mark to assure the drill bit goes in at the exact point you want it to.