Best tool or blade for cutting thick fibreglass

StefanSG

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Trying to chop an old hatch surround out of the deck of my catamaran, its solid fibreglass, I tried today with a reciprocating saw with a newish wood blade, the blade overheated and went blunt after a foot, should I go slower, use a different blade, or a different tool ? Id rather not use a grinder if possible due to the dust. Deck is about 1/2" - 3/4" thick.
thanks
Stefan
 

john_morris_uk

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Trying to chop an old hatch surround out of the deck of my catamaran, its solid fibreglass, I tried today with a reciprocating saw with a newish wood blade, the blade overheated and went blunt after a foot, should I go slower, use a different blade, or a different tool ? Id rather not use a grinder if possible due to the dust. Deck is about 1/2" - 3/4" thick.
thanks
Stefan
GRP blunts most tools very quickly as you’ve discovered. I’ve had some success with tile cutting blades in a jig saw. Alternatively TCT cutter in a router.
 

john_morris_uk

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PS the latter is exactly what I’m going to be using tomorrow afternoon as soon as I get to the boat after work. Same problem except it’s sandwich construction with GRP either side of plywood. I’m replacing a Gebo hatch over the aft cabin with a Lewmar hatch.
 

Boathook

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I use metal cutting blades in a jig saw. Another option is a dremel with heavy duty metal cutting discs but I suspect that your deck is to thick. If you can have another person holding the vacuum cleaner tube close to the cutting wheel it does make a big difference.
I have started to recently use a multi tool on fibreglass but still not sure on the blade to use, either wood or metal.
 

Neeves

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I use an angle grinder with the thin blades used for tiles, Abrasive 'impregnated'. I've had the one I use for years (and have only used it once or twice to cut tiles. For round corners I cut out using a small hole saw bits used for cutting holes in HT steel or a conventional larger hole saw first and then join the holes with the angle grinder. Long slow curves are a challenge. The tile blade will cut through wood - but tends to burn its was through rather than cut.

The offcuts from the hole saw can make good backing plates.

Waste not, want not

Jonathan
 

zoidberg

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It's probably advisable, if cutting thick grp, to use blades designed specifically for the job. e.g. DeWalt DT2056QZ Jigsaw Blade Extreme TC Tipped blade for Fibreglass T341HM : Amazon.co.uk: DIY & Tools

It's also certainly advisable to use 'full-on' PPE, for tiny glass fibres lodged in the bronchioles will certainly kill you, albeit more slowly than coronavirus. A filtering half-face mask of Grade FFP3 D - better still, a Half Face Respirator with P3 Cartridge - is what is needed, together with eye protection. Here's one source of info - Dust Mask Ratings: FFP1 vs FFP2 vs FFP3 - The Ultimate Guide

Such masks need to be properly fitted - otherwise it's a waste of money and a self-deception.

Builders merchants e.g. Travis Perkins, Tool Station, Screwwfix, have supplies.
('scuse my digital stutter )
 
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dankilb

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Any TC coated/tipped blades should work well - I don’t think they need to be Bosch/Makita (although they’re the only ones that specify GRP and also the only ones I’ve used!)
 

John the kiwi

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I am surprised there has been no discussion so far on the jigsaw itself. A few years ago i treated myself to a new jigsaw to replace the old fixed speed handyman pos that I had before. It has a wide range of speeds and adjustable blade swing. (note sure of proper name, but the blade swings back on the down stroke, disengaging the teeth and forward for the cutting stroke.
There is no comparison to the old handyman unit - especially if metal cutting. I havent tried fibreglass.
 

dancrane

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29th November 2023

I need to cut up my GRP dinghy, or pay to keep it where it is for another year. Sad, because I had hoped to sell or give it away, but there are no takers.

I have a fairly new Bosch 18v grinder with plenty of batteries and several of the very thin DeWalt diamond/steel cutting discs.

I'm only reluctant because I want to minimise the dust (although the dinghy's hull is much lighter than the OP's hatch surround, so will be less work).

Perhaps I should go at it with a sledgehammer, although I need the wreckage to be neat manageable pieces to take to the dump.

I could probably be persuaded to invest in a Bosch cordless jigsaw or multitool, which would work with my batteries.

What's the best tool for quick results, on the basis that I really don't want to be crouching in clouds of deadly dust?
.
 
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