Diamond Grit Hole Saw for GRP

[Ian_Rob]

I am planning to drill a 70mm dia hole through the GRP transom of my boat to take a shorepower socket. I have got a Starrett diamond grit hole saw for this and was planning to tape over the area before drilling. Do I need to take any other precautions to prevent the gel-coat cracking other than drilling at low speed?

 

[MoodySabre]

When I fitted a pumpout cap about 60mm to my deck I just used a normal hole saw. It didn't crack or split and I didn't do it slowly. Ditto the clamshell 38mm vent on the upper rear side of the hull. The transom may be a bit thinner.

 

[PetiteFleur]

Agree using a standard hole saw - my transom was 12/13 mm thick!

 

[salar]

I have done this many times. Cover the area with masking tape to help prevent slip, and start drilling at a angle then straighten up, also to help prevent slip. If you drill stright with a hole cutter without a pilot drill you may skitter around and make nasty scratches. The core of the transom may be ply, in which case you need to swap out the diamond grit for a toothy saw when you get to the ply. Diamond saw is best for a clean cut in GRP.

 

[Ian_Rob]

Thankyou!