Holesaw for fibreglass?

I used an ordinary (bi metal) one to cut holes in the grp bumper on my old Rover for reverse sensors and it gave a perfect hole. I'd say it would be ok on acrylic too - but keep the speed very low to avoid melting it. Perhaps lubricate with water.

I have used the standard BiMetal ones and they worked fine on a GRP bath. Also with baths, most fittings will be designed with a flange that would cover any chipping anyway.

Before you go mad on holesaws, consider a step drill?

They are a round drill thus avoid the 3-sided hole of normal drills and self-centre so if you centre-drill a hole to begin with they do a very good job of ensuring the resulting hole is where you want it. The downside is their depth is limited to about 4.5mm (it varies, just look at the engineering drawing of the tool if available). Wonderful tools for enclosures, glass reinforced polyester, ABS, polycarbonate etc.

js.b1 wibbled:

Thanks to you and John. My holesaws are bi-metal and in addition to Dave's suggestion of water as a coolant, the bloke in Screwfix who's keen on kit cars (much fibre glass) recommended applying tape over the surface too to avoid chipping.

On the step drill front - I've never used on but it also sounds interesting - I'll have a look into this.

Cheers

Tim

Again if you use a slow speed and don't push too hard grp shouldn't chip. But as was said whatever you're fitting to it will have a flange to cover the hole edge.

Their main use is in sheet metal - they make a better hole than a normal twist drill. I got a set at my local Sunday market for far less than most charge - and wasn't expecting much of them. But they turned out to be very good indeed.