RotoZip & cutting fiberglass

[WTunnessen]

Has anyone else used a Rotozip tool to cut fiberglass?

Over the weekend I used mine to cut opennings in for access ports in the anchor locker.

This worked pretty well - but I am not sure I found the optimal set up - if there is one.  It did cut nice round circles with out chipping the gel coat.

I used a metal cutting bit and it seemed to work best at the "25" speed setting.   Lower RPM than that cut too slowly and higher caused a lot smoking.  The cutting went pretty slowly but I did not want to push it too much.

I'm planning on cutting two more round holes for speakers, so I figured I'd see if anyone else has found an optimal set up or suggestions for using the Rotozip.   I'll also try to find the multi bit that says its rated for fiber glass.

Its been a pretty handy tool for alot of other applications as well. 

[Roc]

If you are cutting round holes for speakers, a hole saw connected to your drill works.  That's what I've done when cutting round holes in fiberglass. If you're cutting squares or rectangles, I've done it with a jigsaw using a fine toothed blade.  Just make sure when cutting a square, to 'round' the corners and not make them sharp (pointy).  I've used a hole saw bit for the 4 corners to give them a radius.  Then I make straight cuts using the jigsaw for each side.  Go real slow and follow your line and you'll get a nice clean and straight cut.

[Michael Shaner]

I think I installed 6.5" dia. speakers in the cockpit...not sure they make a hole saw that large, that is affordable anyway. I used a 1/8" drill bit in a Dremel...RotoZip sounds similar...

Roc's advice with drilling for rounded corners is most excellent...

[Roc]

Michael is right about an affordable hole saw, especially if you need something large.  If that's the case, see if you can borrow one. 

[Mert Gollaher]

I cut the holes for our cockpit speakers with a Dremel tool and its 1/8" multi-purpose cutting bit.  The packaging says it's good for fiberglass, and it worked quite well.  It threw off lots of dust so I set up a shop vac very close to the cut to draw the dust before it got all over the place.  With a narrow nozzle on the end of the shop vac hose I was able to get enough air flowing through the cut so there was surprisingly little dust on the back side of the cut as well.

Mert

[jmnpe]

I have been using my original "one speed" RotoZip for cutting everything imaginable on boats for about 10 years, including fiberglass. I especially like it to use free hand ( primarily on wood with or without fiberglass cloth over it ) in areas where you can't get ( or use ) a hand saw or jig saw. You can get very close in the corners of 3 meeting surfaces, something that is very difficult with anything else. Just make sure you one hand it very carefully with a good gripe: when the RotoZip take control from you, it can do lots of damage in a very short period of time.

When cutting a hole in fiberglass, it doesn't have to be as messy and dusty as you might think: if you move carefully and deliberately, most of the dust will stay put as it "back fills" the cut you just created. Before you complete the final cut, use the shop vac to go around the "back filled' cut and you can capture most of the fiberglass dust before it escapes all over you and the rest of the boat.

For use on fiberglass, just make sure you you have plenty of bits available. You can extend the useful life by using the cutting edges at different distances from the end of the bit for different cuts: the bits only dull in the area where you are actually cutting  .

I consider the RotoZip to be one of my primary boat tools.

John