90mm hole saw needed for GRP

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Boo2

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Hi,

I need to put a couple of 90mm holes through my new instrument pod which is 5mm thick (or thereabouts) GRP. I have seen some diamond tipped hole saws on eBay here : http://www.ebay.co.uk/itm/Diamond-H...Garden_PowerTools_SM&var=&hash=item462e4e4ec2 at a reasonable price, can anyone tell me whether they are suitable for my needs ?

Otherwise, where can I buy a suitable 90mm (89-91mm) hole saw ? Bosch don't do one in their excellent Progressor series and I don't want to pay the earth. either for just 2 holes...

Thanks,

Boo2
 
You don't need diamond-tipped for GRP. A regular steel holesaw will do the job perfectly well. Just pop '90mm hole saw' into such as Amazon and you'll see plenty.
The glass fibres blunt such tools quite quickly, but it'll certainly out-last your two holes by some distance. Do not opt for the cheap nesting variety: they're rubbish. And drill an accurate pilot hole first: less chance of the holesaw skidding about.
 
Have you considered drilling smaller holes and then cutting between the holes with a jig saw, assuming there is room for a jig saw. Or just drilling a series of close centred holes and using a small pad saw to cut between the holes. A rasp can then be used to round off the hole. I assume the instruments have a bezel which is larger than the hole diameter to give a clean finish.
 
BlowingOldBoots said:
Have you considered drilling smaller holes and then cutting between the holes with a jig saw, assuming there is room for a jig saw. Or just drilling a series of close centred holes and using a small pad saw to cut between the holes. A rasp can then be used to round off the hole.
Click to expand...

Far easier and quicker to just use a hole-saw, though. About seven or eight quid delivered for that sort of size, why spend longer making a raggedy hole (even if it will be covered by the instrument) just to save that sort of money?

Pete
 
prv said:
Far easier and quicker to just use a hole-saw, though. About seven or eight quid delivered for that sort of size, why spend longer making a raggedy hole (even if it will be covered by the instrument) just to save that sort of money?

Pete
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Because the OP does not want to pay the earth and obviously cant find low cost hole saws. It is easy to find low cost hole saws, so I assume the low cost hole saws actually cost the earth as far as Boo2 is concerned. Why do I need to justify my answer to you?
 
Defo use a standard wood hole saw - avoid using a jigsaw if you can - they can be a pain to control in tight spaces and turns especially if you don't have clearance/room for the saw to run flat on its base as you cut.
 
Boo2 said:
Hi,

I need to put a couple of 90mm holes through my new instrument pod which is 5mm thick (or thereabouts) GRP. I have seen some diamond tipped hole saws on eBay here : http://www.ebay.co.uk/itm/Diamond-H...Garden_PowerTools_SM&var=&hash=item462e4e4ec2 at a reasonable price, can anyone tell me whether they are suitable for my needs ?

Otherwise, where can I buy a suitable 90mm (89-91mm) hole saw ? Bosch don't do one in their excellent Progressor series and I don't want to pay the earth. either for just 2 holes...

Thanks,

Boo2
Click to expand...

Have one on the boat. Used 3 times, once for practice and then 2 speaker holes! P.M. me if you want to make me an offer.
Could try dremel with tile cutter attachment?
 
BlowingOldBoots said:
Because the OP does not want to pay the earth and obviously cant find low cost hole saws. It is easy to find low cost hole saws, so I assume the low cost hole saws actually cost the earth as far as Boo2 is concerned. Why do I need to justify my answer to you?
Click to expand...

If you'd followed Boo2's link you'd have seen he was contemplating spending £15.20, or about twice what he needed to pay, so your concern for his penury is perhaps misplaced.
 
Boo2 said:
Hi,

I need to put a couple of 90mm holes through my new instrument pod which is 5mm thick (or thereabouts) GRP.
Click to expand...

I cut 100mm holes for a couple of small ventilators with a jig-saw attachment on an electric drill


Should be easy-peezy with a jigsaw fitted with a narrow blade ( I used a standard blade) if you have the room to manoeuvre.
 
How much did you spend on the instrument panel and are now cheap skating over £20 to fit it yourself?

I struggle to understand thinking like this.
 
Use a standard hole saw. Drill the pilot hole carefully and then turn the pilot drill around so that it runs ion the pilot hole on the plain shank. This reduces the chance of the pilot hole enlarging.

Cut at a slow speed and rock the saw around to keep it cool and to reduce the torque on the drill.

Filing tends to try to delaminate the grp so clean it up with a sanding pad by rotating around the hole rather than filing in and out.

A slight bevel makes for a clean look, provided you have sufficient land on the bezel.

Best of luck.

Tony.
 
It's frustrating that the nearest Bosch holesaw is 86mm.
You could cut out 86mm holes and then use a flap wheel to open them out.
I've done this. Didn't take long to open out the holes with 40 grit flap wheel from Toolstation.
 
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