Marine Electronics Forum - rotozip good for cutting fiberglass?

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08-10-2006, 10:28 PM
Ready to do some cutting for stereo rotozip as good as anything? Any particular blade?

Team Ruby
08-10-2006, 11:22 PM
I have used a rotozip on four boats now. I have found the results to be a mixed bag. The first two boats the tool went through a lot of bits. I found that I was trying to move the tool too fast through the material, the blades was glowing red and dulled quickly. When I tried it at a slower pace, slow enough to keep the bit from turning red, the tool worked better but it took a long time to get through the material. I just did a new boat a few weeks ago and the bit went through the console with no problems whatsoever. The bit was out of the same pack that I had used months earlier with less than stellar results. This time the same bit was used to cut all of the holes required, something I had not been able to do previously. I would tell you to try it, go slow at first to keep the bit from getting too hot and increase your cutting speed and see how the bit handles the material.
Team Ruby

08-10-2006, 11:37 PM
tip #1 (saves A LOT of time, gives MUCH better results and will also save you some money): use ONLY the dremel solid carbide bits when using a roto-zip to cut fiberglass. they cost like 5x as much but last 20x longer. use the hss bits from rotozip and you'll either need to change bits every inch or start burning resin, pushing too hard on the tool to give control, or both.

tip #2: don't use a roto-zip unless you have to. they can fit into some tight areas, but they are much harder to control than a jig saw. if you have the choice, a reciprocating air saw is the best solution. gets into tight areas, is powerful (assuming you've got a decent compressor), and easy to control. that said, i still use my roto-zip when the situation calls for it.

08-10-2006, 11:42 PM
make sure you tape off the area your going to cut so you dont chip the fiberglass

08-11-2006, 12:07 AM
Ugh, rotozips make way too much of a mess. Better to just use a *decent* jigsaw. You'll get nowhere near the massive amounts of dust a rotozip will kick up. And giving that it's fiberglas you don't really want it airborne. It's bad enough getting it on your skin but breating it is even worse. NO THANKS.

08-11-2006, 10:47 AM
I have cut holes with a jigsaw before, and this last time used a rotozip *with the circle cutting guide*.

I was VERY happy with the rotozip. I was cutting through thin (1/4" fiberglass) and it went very smoothly. The hole guide made a tremendous difference, and clearance with the rotozip tool while not perfect was better than the jig would have been. I'll admit I didn't even mask the area, just marked the centerpoint, drilled a hole for the circle guide, and went to town.

On Glen's recommendation I cleaned the edges up a touch with a sanding drum in my (cordless) drill and that took care of a couple small wavy spots.

My results with a jigsaw in the past were decidely worse. Nothing like kneeling on your deck between the console and hull, trying to cut a circle 4" off the floor....

The Rzip did kick up a lot of fiberglass dust, but that cleaned up quickly with a shop vac.

Don't know why my experience was so different, but IMO this was better than a jigsaw and definitely better than the disaster I had trying to use a dremel.

Team Ruby
08-11-2006, 11:39 AM
Good point about the dust a rotozip kicks up. I had another person hold the shop vac nozzle right next to the bit from inside the console and we had very little mess to clean up.
Team Ruby

08-11-2006, 11:40 AM
I like the dremel with the ceramic disk to make the straight line as deep as it can, then a carbide cutting bit.

08-11-2006, 11:54 AM
Iím presuming the poster hasnít used a Rotozip before and hence his question.

If you have never used a Rotozip there is a learning curve to them. Some folks donít have what it takes to stick with it and learn how to use the tool. But if you do, and it take a little time and practice, the Rotozip can be a wonderful critter. As was mentioned, they tend to throw dust around, but you will learn that as you go thru the learning curve BEFORE you ever start cutting on your boat.

An alternative is a Dremel tool, similar to a Rotozip but smaller in size. (I believe Dremel founded Rotozip, then sold it off, but both are now owned by the same parent co.) As was mentioned above, a Dremel with the tungsten bit will work wonders at cutting irregular shapes. And because the Dremel is smaller it is easier to control, less of a learning curve. But the Dremel also kicks around the dust like the Rotozip.

Unless you have the need for a Rotozip after this boat project I would say pass on it as the tool of choice. Itís too much tool, too much learning curve for a one-time use. Iíd opt for either a Dremel or a reciprocating saw as was also mentioned above.

08-11-2006, 12:02 PM
Eyeball - 8/11/2006 10:54 AM

Iím presuming the poster hasnít used a Rotozip before and hence his question.

Just for the record, I hadn't either - I borrowed one from a friend. I have a dremel and had a completely miserable time trying to cut out the opening for my CD player. (there was no clearance for a jigsaw OR a rotozip)

I will reiterate that I think using the circle-cutting-jig for the rzip made all the difference - freehand would have been a disaster.

I did one test cut on some scrap plastic and then went at the boat. Had no issues. With the dremel (freehand) I had horribly wavy lines because the bit was constantly trying to make my turn curve to one side or the other as it bit in. With the rotozip and it's guide attachment, there was nowhere for it to go as long as I applied steady pressure and made sure the guide was snug in the center hole.

After using it, I would consider buying one. Again, this was thin console glass, not the side of my hull, but I was pretty impressed. And I have burned through all 300 of my dremel kit bits without yet finding something that it is truly good at.

08-11-2006, 12:08 PM
Good point AdamLotz; whatever is use, a guide for the tool is a good idea.

I haven't done a one for one comparison but I think pretty much any cutting guide/option that is available for the Rotozip is also available for the Dremel; except the Dremel has more cutting options (bits). And as you mentioned, I wouldn't use it free hand unless there was a big, fat face plate on the stereo that will cover up the sloppy cut.

Fwiw, there are aftermarket cutting bits available for the Rotozip that have a reverse spiral (cuts pulling into the material on BOTH sides!). They are made by one of those high-end router bit companies.

08-11-2006, 01:08 PM
I went and looked at roto's and dremels. I also found a carbon blade for cutting fiberglass with a jog saw and a reverse tooth (cut on down stroke) 10tpi blade for a jig saw. I am wondering if thats the way to go. Is it really worth buying another $100 tool for this one job. The point is to save money otherise i might as well have the installer do it and save me the trouble.

08-11-2006, 01:35 PM
I prefer a jig saw with a fine tooth blade. Thoroughly tape up the area first.

08-12-2006, 10:31 PM
I have used both thru the years--recently revisited the newer Rotozip, and did a 14 x 14" hatch with only 3 bits. Went very slow. I have a vacuum attatchment on the rotozip which picks up most of the dust. It is slower than a jig/saber saw, but much cleaner cut. I didn't tape and had no lifting or cracking of the gel coat. If it is a one time cut and you have a jig saw, get the correct blade, tape and go. If you have a lot of holes, then I think that the Rotozip is worth it, especially with the attatchments. For straight cuts, I also like a small circular saw (carbide blade tips) and definately tape. I did a lot of samples cut out of hurricane damaged boat hulls for some ultra sound testing, and cut about 100 lineal feet with no discernable damage to the carbide blade in a circular saw.--again, go slow and tape. I also always drill my corners, no matter what tool I am using.

09-04-2006, 11:27 PM
I bought a Rotozip and tried it on fiberboard (the backing to a TV cabinet). It did a very poor job and I returned it. Asking on THT produced mostly negative responses about the tool.

Next time, I will use my jig saw with a fine blade.

Has anyone tried a laminate cutter with a spiral or straight bit? I wonder if they might be more suitable to the type of cut we need, perhaps smoother and more controllable due to the extra weight and power. A quick search turns up fiberglass router bits fro Bosch.

09-05-2006, 12:39 AM
Has anyone tried a laminate cutter with a spiral or straight bit? I wonder if they might be more suitable to the type of cut we need, perhaps smoother and more controllable due to the extra weight and power.

I dought you will see a nickel's worth of diffrence.

09-05-2006, 09:59 AM
I still can't find a decent jigsaw blade that will last longer than 4". Any ideas?

09-05-2006, 10:17 AM
What style of blade do you need? T- style that fit's a Boush or the old style that fit's most other saw's?

Either way. Home Depot here has the Remington blade's that have grit on them. A little xpensive but the work very well. I can't find them for my T style Boush saw. I use Bi-metal 14TPI or 18TPI blade's.

Hooked Up Again
09-05-2006, 11:47 AM
How about A SAWZALL, I was think of using that on my Pursuit dash, anyone ever try that?

09-05-2006, 12:48 PM
A sawsall is used more for demolition. You will not have near the control as you will with a jigsaw.

09-05-2006, 01:02 PM
sawzall is good, but i think a CHAINSAW w/21" bar would be better/faster

09-06-2006, 11:17 AM
warthog5 - 9/5/2006 8:17 AM

What style of blade do you need? T- style that fit's a Boush or the old style that fit's most other saw's?

Either way. Home Depot here has the Remington blade's that have grit on them. A little xpensive but the work very well. I can't find them for my T style Boush saw. I use Bi-metal 14TPI or 18TPI blade's.

I'll try those. I have an OLD Craftsman. Still works though. Sorry to hijack this thread. :trout:

09-06-2006, 09:49 PM
The reverse tooth jig saw blades work great on fiberglass. They are made for laminate and help to avoid chipping the gel coat. I use them and I tape the area off. Mostly I tape the area off to avoid the little scrapes that can come from turning the base of the jig saw over the gel coat. I don't use roto's any more because I had a blade break on me and the tool went straight into the cushion that was next to the hole I was cutting. Four inch rip's are tough to explain.

09-08-2006, 03:08 AM
Go ahead and laugh about using a sawzall but at times it is the best tool for the job. I've run into enough install cuts that just won't allow any kind of a power tool down on the surface of the cut due to clearances to other equipment or to adjacent perpendicular panel surfaces.

Here's the deal. Get the 14" long, fine tooth sawzall blades. They are about a 3/4" wide so as-is they won't cut nice curves. I take my small air driven cut-off tool or 4" grinder and cut about 1/2" off the back of the blade about 6" along it's length with the blade mounted in a vise. This gives you a sawzall blade about the same width as a jig saw blade. Drill 3/8" dia holes in your panel at any corners of straight cuts or at least one 3/8" hole at the edge of your planned circle cuts. Load up your modified (slimmed down) blade in a variable speed sawzall and start cutting, very slow at first until you get used to freehand cutting along your pencil lines.

It works amazingly well and you'll find you can do all kinds of tough cuts very easily. I've got all the tools mentioned above and I pretty much use my sawzall now on even the easy access cuts.

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