90mm hole saw needed for GRP

[David2452]

Hi,

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

But they do a 92mm one if that works for you part # 2 608 584 653. Starrett also do a constant pitch one 89mm that might suit, part # SH0312. use both extensively in GRP without issue.

 

[salar]

The larger the hole saw, the bigger the strain on the drill motor due to the leverage so you will need a powerful drill to drive it. The alternative is to use smaller hole saws, don't cut all the way through initially and make a sort of clover leaf pattern to fill the large hole you want. Then you will only have a few nibs to smooth out with a curved file. I like to use tile hole saws on GRP, the finish is better and it is more controllable but does not have a pilot hole so you need to tape on the guide supplied. Here's the dash I made up:
http://i245.photobucket.com/albums/gg52/flying-ferrets/NewDash.jpg

 

[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.

Yes, I threw away a cheap nested set because it was literally useless.

I can get the diamont type quite easily and quickly and £15 is not too much, my question really relates to how suitable they are for glassfibre work ?

But they do a 92mm one if that works for you part # 2 608 584 653. Starrett also do a constant pitch one 89mm that might suit, part # SH0312. use both extensively in GRP without issue.

Thanks, that's interesting, 92mm might be OK but I think 89mm will be just too tight.

If the diamond types work OK on GRP then I will try to find one in Brighton Tools and Fixings tomorrow, I am unexpectedly availed of a few days off to do this job so would rather spend a few quid on a drill that I'll only use once than wait...

Boo2

 

[nigelmercier]

I suggest that for GRP you use a bi-metal cutter. Here is an 89mm Bosch for under £10: http://amzn.to/1ECSRMS

If 89mm is too tight (which I don't think it is) this is an ideal job for a sanding drum: http://amzn.to/1HciTEw

 

[Tomahawk]

From experience, the problem with hole saws is the lack of any way for the sust to be extracted. This leads to heat which is what runis the saw. I overcome this by running a few turns with the hole saw to mark where it will cut the matial then drilling a couple of "drain" holes on the cut line to let the dust excape. A vacuum cleaner also helps..

 

[KellysEye]

>Do not opt for the cheap nesting variety: they're rubbish.

I had those and used them with no problems, if you have a range of sizes they will obviously nest.

 

[macd]

>Do not opt for the cheap nesting variety: they're rubbish.

I had those and used them with no problems, if you have a range of sizes they will obviously nest.

By 'nesting' was meant the type with an assortment of flexible blades that engage in a shared base. Clearly one-piece hole saws of different sizes will also nest.

 

[parbuckle]

Shame not quite big enough or is it http://www.screwfix.com/p/bi-metal-holesaw-86mm/18572