Hole Cutting for ventilators.

[bob_tyler]

I am considering adding a couple of mushroom vents on the cabin top of my Invicta which is very solid glass fibre ( no balsa weightsaving in those days).

What is the best tool for cutting the necessary rather large hole in the neatest possible way and where can I get it?

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[Evadne]

I would suggest drilling a 10mm pilot hole then using a jigsaw with a new blade.

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[bob_tyler]

I can rarely get a straight line with a jigsaw, much less a perfect circle.

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[kds]

You can get half-depth blades which make it easier to follow the line. Take it very slowly indeed and make sure you err on the inside. I then cleaned up with a barrel shaped coarse sandpaper on a foam barrel on a drill.
Good luck,
Ken

<hr width=100% size=1><A target="_blank" HREF=http://www.canongrange.co.uk>Bed and Breakfast, cathedral Green Wells, Somerset Canon Grange</A>

 

[Nauti Fox]

What diameter are t'holes?

<hr width=100% size=1>No dear,the water goes in the other one.

 

[pvb]

You could always...

As already suggested, I'd use a jigsaw or even a hand padsaw. But if you really want a neater hole, you could always buy a proper holesaw - <A target="_blank" HREF=http://www.screwfix.com/app/sfd/cat/cat.jsp;jsessionid=CDU3IKBM3LHGVCJO2C1CJ0Q?ts=93114&id=100220>Screwfix</A> have them quite cheaply up to 152mm diameter.

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[ccscott49]

Most hire tool shops have hole saws to rent. Get a good one, ask the guy/guyess for a new blade. the cheap screwfix ones are ok for light use, but you need a good industrial one.

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[snowleopard]

i'd contest the assertion that screwfix holesaws don't last. i bought a set when i started building and have since cut a great number of holes in grp and they're still going strong.

if you want to cut more than about 60mm diameter you'll overload a domestic drill so you'll need to hire an industrial drill too, it's starting to get a bit expensive.

if you use a jigsaw, choose a metal-cutting blade, preferably the bi-metallic type. the teeth still wear away but they should cut 20-100 ft, depending on thickness, before needing to be scrapped. there should be room for a bit of wobble hidden under the fitting. as said previously, you can always open out an undersize hole.

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[cliff]

Now boys, don't fight over messers Screw (the public) fix.

When they started their products were crap, like the cheapest and nastiest one could find, but now some of their stuff (non branded) if O.K. but remember - you only get what you pay for. If using Screwfix's hole saws get your hands on a saw setter and set the teeth alternately in/out to leave clearance for the "can" to enter the hole and not jam on either the core or the base material.

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[snowleopard]

don't know how old yours was - mine were bought in 98 and are the same type sold currently. the teeth are set as you describe and are still sharp.

i know it's fashionable to knock any large company but to date i've not had any duff stuff from them.

i'm currently demolishing a concrete wall using an SDS drill bought from them for under £30.

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[summerwind]

Lesson I learned the expensive way is that when using a holesaw - go SLOWLY. It will of course take more time but you won't wear out the teeth so quickly, the centre hole stays the correct size, you won't break the drill and you get a much better job.

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[kds]

Sorry - don't agree. I have had great value and service from screwfix. Used their tools etc. for most of the 2 years to complete my 29 ft. and they are still going strong.
Ken

<hr width=100% size=1><A target="_blank" HREF=http://www.canongrange.co.uk>Bed and Breakfast, cathedral Green Wells, Somerset Canon Grange</A>

 

[Strathglass]

As Cliff said, you only get what you pay for. I have been using S'fix for many years.

They now stock a lot of more 'Profesional' tools. The delivery times on larger items is a bit slower. But any faulty item or wrong delivery is instantly sorted out without question.They also keep a good customer record database and are quickly able to tell is any item is still within the guarentee.

I have used their hole cutters on wood, GRP and even stainless without problems (with proper lubrication and speed)
I also have a large tipped cutter (107mm) from them which has cut many holes through brick cavity walls and concrete slabs but it does need a large drill to drive it.

It is very much a case of horses for courses and how we drive them.

Iain

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