Cutting big circular 'oles in fibreglass

[Tillernut]

If you are using a jig saw get yourself some downward cutting blades. You can find them in B & Q etc. if you look hard enough.

 

[dovekie]

You can buy carborundum edged blades for jigsaws, which are absolutely great for cutting grp, and don't go blunt, which in my experience all the metal blades rapidly do. Would certainly cut the 20cm hole, the 8cm radius may be a bit tight. You could practice and see on the scarp piece you cut out of the 20cm hole.

 

[savageseadog]

Use a router and template guide with a suitable circular template. The template and cutter will need to be paired to get the correct diameter. Fix the template with silicone or other suitable adhesive.

 

[TRH]

Hi I paid a fiver in the market for a cheap hole cutting kit. I intended to cut two holes.That was four years ago, between the guys at my marina and myself we have fitted four heating systems,and a number of other things.Keep them sharpe and use tape to cover your work,and take it slow.

 

[exfinnsailor]

Cutting Holes

Bought a hand saw blade from B & Q when I fitted the heating to the boat .. Had to cut 2 x 80mm holes in totally inaccessible places .. Wrapped masking tape round the teeth for a handle and away you go .. Take it easy and you can get a very nice hole .. You can finish off with a half round file .. Blade cost about £2 and still have it .. The blade is about 15mm at one end and then tapers down to about 3mm .. You can also get a handle for them but the tape worked well ..

 

[Wunja]

I bought a set of Bosch hole saws for about 12 euros from my local DIY chain, when I fitted some ST60 instruments, worked from both sides of the hole. You do need a drill with good torque and a full battery though. You will also find as the slot gets deeper, it will start to grab the hole saw, so you need to regularaly pull the drill back and let the cutter rotate at speed and clear the dust from the hole.
For the 200mm hole, I would follow the advice to use a router, but with a radius arm to allow the router to rotate around the centre point of the hole acurately.

 

[Ubergeekian]

I bought a set of Bosch hole saws for about 12 euros from my local DIY chain, when I fitted some ST60 instruments, worked from both sides of the hole. You do need a drill with good torque and a full battery though. You will also find as the slot gets deeper, it will start to grab the hole saw, so you need to regularaly pull the drill back and let the cutter rotate at speed and clear the dust from the hole.
For the 200mm hole, I would follow the advice to use a router, but with a radius arm to allow the router to rotate around the centre point of the hole acurately.

Ta and ta. I have just bought a Bosch router (and disguised die grinder) on eBay.