Drilling Holes in fiberglass Tub and Shower

Hello,
Well here I am with another question. What type drill bit do I use to cut a 3 1/2 inch hole in a fiberglass enclosure and what special precautions to use to keep from chipping the gel-coat?
Thanks in advance.
Katman104

A normal Lenox hole saw. The more teeth the hole saw has the better. A fast turning drill is a must.

I use a Milwaukee hole-hawg for all my drilling...setting it on low to drill tubs.

Keep it straight so it doesn't bind!

A hole saw is the way.Do not use a jig saw.Youcan get one at your local
hardwere store or rent one,

Shower hole cutting...

RUGGED said:

A normal Lenox hole saw. The more teeth the hole saw has the better. A fast turning drill is a must.

I use a Milwaukee hole-hawg for all my drilling...setting it on low to drill tubs.

Keep it straight so it doesn't bind!

Click to expand...

Just a suggestion...if you haven't used a hole saw before(3 1/2 is a good size!)I would put tape over and around the area you are going to cut. Couple of inches bigger should do it.(remove tape after cutting hole.)Find the center of the hole and drill a pilot hole the same size as the bit in the hole saw.(they come with a centerbit to guide you). Guide the centerbit into the hole you drilled and then proceed to drill the hole. This will keep the hole saw from "walking" on you(moving down on the shower wall chewing up the gelcoat!)Follow rugged's advice about drilling slow and keeping it straight. Just before you get all the way thru is when the hole saw will try to bind on you so keep that in mind.
The shower wall is not that thick so if you force it or try to go too fast the hole saw can start to bounce around and possibly damage the shower.
BTW, a metal cutting hole saw is what Rugged was describing with "many small teeth" as opposed to a wood hole saw with "less big teeth."

As always, use gloves, eye protection, etc...

Thanks to all that answered I appreciate the information and will try to pick one up today at Lowe's if they have one. At one Lowe's store they tried to sell me one that I did not think had enough teeth to it so I did not buy that one. Decided to wait and post on this forum for information. Glad that I did.
Again thanks to all that responded.
Katman104

If you're installing a Delta monitor series....I always used a 4-3/4" hole saw, the same one I "used" to drill for my closet flanges.

Ahhhh the memories. Bad thing is I got to drill for one this coming week.

hole

If you use the right sized cutter the chrome trim plate will cover any chips. I have used either a hole saw or a fine toothed narrow SawZall blade to cut the holes.

RUGGED said:

If you're installing a Delta monitor series....I always used a 4-3/4" hole saw, the same one I "used" to drill for my closet flanges.

Ahhhh the memories. Bad thing is I got to drill for one this coming week.

Click to expand...

When you are drilling holes for closet flanges, do you always remove the flange, drill the hole, and then replace the flange? If you didn't remove the flange, wouldn't you would have to drill the hole and then piece in the subfloor to get it under the lip of the flange?

Thanks to all that answered, I bought the 3-1/2" hole saw and will attempt this coming week.
katman104