Using a Holesaw into fibreglass - any tips

gandy

gandy

Well-Known Member
Joined
24 Aug 2004
Messages
3,404
Location
Aberdeenshire (quite far from the Solent)
Visit site
Hi,

I need to cut a 50mm hole though a surface comprising fibreglass with wood or plywood bonded onto it. Maybe 20mm total thickness. The top surface is white gelcoat, and will be visible after I've completed the work.

Any tips for using a holesaw to minimise chipping of the gelcoat? This is one job where I can't practice on a scrap first.

Ta in advance.
 
If you can, drill from both sides, it gives a cleaner hole. I had thought a time or two that some wax might help but I havn't tried it myself.
 
Should not be a problem. Just cut from the outside in rather than the other way around and ensure your hole saw is nice and sharp.
 
A good holesaw gives a lovely clean edge. It is just worrying in advance. To state the obvious, though, make sure you make it in the right place!
 
Found a "tile" holesaw, the type with carberundum grit rather than teeth makes a lovely job on GRP with no chipping, available from B & Q quite cheaply. Also works well on laminate.
 
With any hole it is neatest if you go 3/4 of the way through from the outside, then use the small drill hole for alignment to drill in again from the inside, clearance permitting.
 
As advised on p137 of the current PBO. Slow speed and allow the tool to do the work without pushing hard. Keep it square.
 
I second all of the advice here and only post to say that we made 4 holes in the pilothouse side this weekend to fit new instruments - 102mm diameter through nearly 30mm of GRP / hardwood ply sandwich.

Going slowly, stopping 3/4 way through and finishing from the other side has left a lovely clean space. Did all 4 in half an hour.

We started out with a jigsaw but after 20 mins and a lot of swearing we had a tatty half cut circle and decided to go and spend 20 quid on the holesaw which did the job a treat.

We used the bi-metal saw - the hardware shop didn't think the diamond tile ones would work well on GRP but they may be wrong as others have posted.
 
You could drill a slightly smaller hople and file or use a dremmel to bore it out , takes longer but more control.

But however you do it remember GRP dust is not good for you so cover up, I did'nt and after a lot of exposure to the dust ended up with blisters to hands and face and that lasted for months. Not nice!
 
Exactly what we did - masking tape over the area we wanted to cut in and then carefully drill through - started off low speed as we were cutting an oval (hole saw at an angle) and didn't want it to kick .... easy job in the end!
 
All good tips only other thing i would do is tape nozzle of hoover next to hole whilst drilling, keeps it neat, you can see what your doing and your not breathing in the dust.
 
The problem with hole saws, especially when drilling through thick materials, is that there is nowhere for the waste to go - it just clogs up the teeth of the saw. To avoid this, drill a small hole (say 6mm dia) which just touches the circumference of the hole made by the hole saw (obviously in the waste bit, not on the outside of it). The teeth can then clear themselves every revolution, won't get clogged and you won't get the heat build-up.
 
Thanks for all the tips. I won't be able to drill from both sides in this case, but I should be able to clamp a block of scrap underneath to stop breakout. Hoover and masking tape are both useful suggestions.

As is making sure I drill in the right place.
 
You must log in or register to reply here.

Share this page

Top