Rotozip tool for cutting fiberglass?

JonnyBoats · Post by **JonnyBoats** » Sun Jun 17, 2007 3:25 pm

If one wants to cut a hole in a fiberglass cabinside for something like a port, what would be a better tool, a rotozip or a jig saw?

CharlieJ · Post by **CharlieJ** » Sun Jun 17, 2007 4:31 pm

depends on how thick. I've used both AND I've used a router with a pattern bit running inside a pattern. My personal preference is the jigsaw and routerbecause then the cutout is precise, but of course you must make a pattern first.

The Rotozip does a very good job, but be warned- use a carbide bit- fiberglass will turn a high speed bit into a rounded stick in just a few inches of cut.

Figment · Post by **Figment** » Sun Jun 17, 2007 8:56 pm

Use of a carbide bit in the jigsaw (the mega-abrasive kind sold for cutting tile) makes the cut far more controllable, I think.

Post by **Tim** » Mon Jun 18, 2007 6:02 am

A jigsaw will do just fine for what you intend. You can easily follow a line closely enough for a port installation.

For something where you needed a highly accurate cut, the router and pattern jig setup would be the only way to go.

I find Roto-Zips barely tolerable even for cutting something like drywall, so I won't recommend one of those for anything, much less regular cuts in fiberglass. As a tool of last resort, they work adequately. But they just make way too much noise and dust for the good they do.

Quetzalsailor · Post by **Quetzalsailor** » Mon Jun 18, 2007 8:54 am

John,

I have a dandy heavy duty Bosch sabre saw (what others sometimes call a jig saw; I trash-picked a huge old cast iron jig saw, got it working, and it ain't the same thing!). My Bosch's variable speed, not as large as some of the bulky older versions. You can get one, and a handful of blades which are not too expensive, at the Despot. It's more than adequate and fast. Toss the blades as soon as the performance drops off (less speed, discolored metal, shiny tooth tips). Get the variety pack of blades so that you can pick the best performer. I find that the agressive wood-cutting ones do fine.

The Tee-mount blades are a love-hate item. You have to be unusually strong and coordinated, and immune to heat.

For your foam-core cabin top, a sabre saw will be more than adequate; there's really not much glass there. It was far less happy with my homemade throughhull backer blocks! Experiment with which blade gives you the least tear-out and chipping for an adequate time expenditure.

I don't know where you are operating, but recall that LeComte buried electrical conduit in the core!

The router is dandy for smaller, but neat and perfect shapes; best with a jig to cut down on unhappy excursions. I use the solid carbide 'end mills' for routing 'glass and aluminum.

Figment · Post by **Figment** » Mon Jun 18, 2007 9:23 am

Quetzalsailor wrote: Toss the blades as soon as the performance drops off (less speed, discolored metal, shiny tooth tips). Get the variety pack of blades so that you can pick the best performer. I find that the agressive wood-cutting ones do fine.

I couldn't get a bosch woodcutting blade to go more than 2' in fiberglass without burning up. You seem to have had much better luck, so perhaps I had a bad batch of blades.

I landed on the tile-cutting carbide blades for use with fiberglass because the wood-tooth blades burned out SO quickly. The carbide blade (if you can be disciplined enough to avoid bending it) will last at least 20X as long.