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Best tool or blade for cutting thick fibreglass

StefanSG

Member
Joined
10 Feb 2021
Messages
52
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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Joined
3 Jul 2002
Messages
24,396
Location
Farnham, Surrey
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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3 Jul 2002
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24,396
Location
Farnham, Surrey
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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5 Oct 2001
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5,059
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Surrey & boat in Dorset. Both have pubs
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.
 

Caraway

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11 Aug 2019
Messages
6,067
Location
England
Tape a sheet of polythene (gaffer tape) on the headlining under the hatch. Leave it very baggy and cut with a 1mm cutting disc on an angle grinder.
Leave it 10 minutes before taking the plastic off so most of the dust will have settled into the plastic..
 

Neeves

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Joined
20 Nov 2011
Messages
8,127
Location
Sydney, Australia.
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

Well-known member
Joined
12 Nov 2016
Messages
4,472
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 )
 
Last edited:

thinwater

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12 Dec 2013
Messages
2,824
Location
Deale, MD, USA
Grinder with cut-off wheel and deal with the dust. Five times faster.

PPE. Running a shop vac right where the dust is coming off will catch much of it.
 

dankilb

Active member
Joined
23 Jan 2008
Messages
686
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!)
 

penfold

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Joined
25 Aug 2003
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5,197
Location
On the Clyde
Skinny cutting discs for grinders are only 1mm thick these days, not that much dust and you could deal with it with a vac.
 

John the kiwi

Active member
Joined
23 Nov 2011
Messages
737
Location
Nelson New Zealand
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.
 
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