Cutting Fibreglass

fjarvis · 21 April 2006, 23:28

Just got a new RIB and want to move my ICOM M421 VHF over to it. I'm going to pick up the flush mount kit and fit it to the console. I've never had to cut into fiberglass before, what is the best way to do it? Just drill a pilot hole and use a hole saw designed for wood??

Thanks folks,
Fraser

Tim M · 21 April 2006, 23:35

If you've got a steady hand an angle grinder works very well.

If your using a jig-saw you can get special blades for fibre-glass. However you'd probably get away with a regular wood one with fairly fine teeth for this job. Legend has it if you put masking take over the area to be cut it finishes better. Personally I have never tried this; angle grinder works a treat

AndrewH · 21 April 2006, 23:53

Quote:

Originally Posted by Tim M

Legend has it if you put masking take over the area to be cut it finishes better. Personally I have never tried this; angle grinder works a treat

Masking tape or better still Gaffa Tape. The idea is that is stops the edges of the Gel/Flow coat breaking away from the rest of the GRP. Tried it a couple of times and it really does work

ian parkes · 22 April 2006, 00:58

For a clean cut use down cut blades in a jigsaw . The teeth cut on the down stroke not on the up stroke as per normal . You won't chip the gel coat at all . Tape is also good but won't stop chipping completely .

For small cuts a hacksaw blade in a handle or just with tape wrapped around one end is very good

Hightower · 22 April 2006, 01:46

If I was worried about chipping gel coat I might well cut undersize and file out the last mm or so. You can get file/fret saw attachments for jigsaws and would recommend against downward cutting blades as your more likley to cause more damage if it catches you out.

Nos4r2 · 22 April 2006, 03:12

The thin cutting blades for angle grinders are incredibly good for cutting GRP as long as you only want straight line cuts-I cut everything on my console with one (no tape either apart from on the grinder's spark shield to stop scratching) and it made a beautiful job of it. No chipping, scuffing or anything.

It's difficult to control for small distances though-I found that small stuff was a lot easier with a 3/4 used blade as it was smaller.

limeydal · 22 April 2006, 03:20

Dont know if you get them over there ;but Rotozip are great for glassfibre.

Looks like a mini router but has a cutting tool instead of a shaping tool.(looks like a spiral drill bit ) Nice because you can set the depth of cut to just penetrate so no risk of nicking anything underneath(unlike a jigsaw).No need to drill pilot hole as self starting(just angle the tool).Can "bite" if held too loosly, so firm hold and a piece of guide material taped down if you want a clean straight line. Great tool ,with blades that cut anything from drywall to ceramic tile. Much less chance of gel coat damage than a reciprocating tool

cheers Dal

Endeavour · 22 April 2006, 15:45

Hi all,

We use diamond blades in a 4" angle grinder. I have also used a dremel with the same type of blade. Quite dusty, but a clean cut.

GED · 22 April 2006, 18:22

Quote:

Originally Posted by endeavour boats

Hi all,

We use diamond blades in a 4" angle grinder. I have also used a dremel with the same type of blade. Quite dusty, but a clean cut.

Trust me this guy knows how to do it!!!! he's just done a fantastic job on my 8mt rib

PeterR · 22 April 2006, 19:51

If you look in B&Q 4 inch Diamond blades are only a few pound i would olso recmend them as well .If you use a jig saw make sure you use masking tape this will mainly protect the gellcoat from the metal bottom of the jig saw from marking the gelcoat two layers of tape is best.good luck .Cover every thing up it saves cleaning arfter

fjarvis · 23 April 2006, 11:14

Thanks folks, I'll head down to B&Q and take a look at angle grinders.

That should take care of fitting the VHF, but I'm also planning to mount my chartplotter on top of the console using the supplied gimball bracket (not enough room to mount it in the console unfortunately), so I'll need to drill a large (1 inch) hole to allow the power / NMEA2K / sonar cables to pass through. What should I use to do that? My thinking was a small pilot hole and one of those drill bits that looks like a spade with a small triangle pointing down in the middle, but am worried sbout chipping - will gaffer tape do the job again?

Thanks again,
Fraser

roycruse · 23 April 2006, 11:37

If you mean this sort of thing - I wouldnt use it on fibreglass.

Much better off investing in a proper set of holesaws

http://www.screwfix.com/app/sfd/cat/...88630&id=45172

jwalker · 23 April 2006, 11:50

Whilst I agree with roycruse, I have to say, for a one off usage a flat drill is an ok way to go because the are cheap. They make the back of the the hole ragged as they burst through but if you can get to both sides with the drill, go through until the point protrudes and then drill from the outside to meet the the first drilling. You could buy the cheap version of the hole saws which you'll get in B&Q for a few kwid. They don't last long on fibreglass but they'll do a good few holes before you have to throw them away. The flat drill has the advantage that you can easily sharpen it so it lives for another day.

Nos4r2 · 23 April 2006, 18:51

It's possible to buy a centre and a single blade for a holesaw-that's how I cut the hole for the steering on my console.
It's about 30 quid all in for a good quality one but the job it makes is worth every penny.

You can buy more blades when you need them once you have the centre.

I really wouldnt bother with a cheap B&Q holesaw. The first time they hang they destroy the centre lock and they make a really untidy messy job.

I didn't even have to dress the edges after using the good one I bought.

Tim M · 23 April 2006, 20:24

Quote:

It's possible to buy a centre and a single blade for a holesaw

I have one of these and it's much better than a regular hole saw, as you can adjust it to any diameter.....Plus you can sharpen the blades easily.

slimtim · 23 April 2006, 20:31

Quote:

Originally Posted by Tim M

I have one of these and it's much better than a regular hole saw, as you can adjust it to any diameter.....Plus you can sharpen the blades easily.

Someone post a link of where these can be purchased from? I will be needing to cut a lot of holes soon...I was going to use my teeth, but i'm not sure I can get a clean edge.

Nos4r2 · 23 April 2006, 20:32

Quote:

Originally Posted by Tim M

I have one of these and it's much better than a regular hole saw, as you can adjust it to any diameter.....Plus you can sharpen the blades easily.

Not quite what I meant-I meant you can buy the centre and one blade at a time that are the same as the pic in roycruse's post without having to pay a small fortune for a whole set.

The adjustable one might be worth looking into though.

Nos4r2 · 23 April 2006, 20:43

try this- at £35.19 it'll do everything you want.

http://www.machinemart.co.uk/product.asp?p=060231026

roycruse · 23 April 2006, 20:55

Quote:

Originally Posted by Nos4r2

try this- at £35.19 it'll do everything you want.

http://www.machinemart.co.uk/product.asp?p=060231026

Thats the worse suggestion possible for someone who needs to drill a 1" hole - £35.19 and not a one inch cutter in sight.

The Bosch set I suggested earlier doeas have a 25mm (1") and I can personally vouch for these being supurb quality - they are what I used to drill a 2 " hole for my fuel flow meter last year.

If you want to save £10 here is a cheaper set that also includes a 1" cutter.

http://www.screwfix.com/app/sfd/cat/...e=null&homeRef=

Endeavour · 23 April 2006, 21:02

just buy the arbor and then the hole saw for the size you are going to need. you can buy a different size hole saw and use the same arbor. the sets are not a good idea as you will find that unless you are an electrician or plumber, then you might only use 1 or 2 in the set. just like buying a 100 peice socket set for a 10mm, 13mm and a 17mm.