A 4" and 4.5" hole.

[tomg]

A 4\" and 4.5\" hole.

Bought two new gadgets at the Boat Show, one of which requires a 4" hole through 1/2" thick ply (sorry about the imperial system) and the other (a VHF speaker)needs a 4.5" hole through the fibreglass in the cockpit. Simple says I, buy the right sizes of hole saws (not a multi-size set), low speed in the drill and its done. Not that I've ever drilled a hole that large you undersatand but it can't be difficult can it? So I've tried the 4" in the garage, on a bit of plywood and it's a disaster; it binds and locks up and nearly breaks my wrist. Dare not take it anywhere near the lovely yacht. There is plainly a knack or a trade secret which I don't know - why would I know?- but I urgently need to find a man, or woman, wot does. Please.

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[pvb]

Hmmm...

Hole saws that big can be nasty buggers to use, especially when they break through to the other side. Doesn't particularly matter in out-of-sight places (like drilling bulkheads to take heater ducts). In other places, if you're not happy with a hole saw, you could always drill a circle of 5mm holes close together and then cut between them with a padsaw, finally smoothing with a half-round file.

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[Oldhand]

Re: A 4\" and 4.5\" hole.

You need an industrial sized drill with loads of torque and very large handles. This is best used by taking small "dabs", i.e. pressure and withdrawal, rather than continuous pressure and must be held very firmly. It binds when you go the slightest bit off perpendicular to the hole you are trying to cut so lubricant on the cutter helps.

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[jimbouy]

Re: A 4\" and 4.5\" hole.

Depending on just how accurately round the hole needs to be you might be better off marking it, drilling a hole and then cutting it with a pad saw.

Jimbouy

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[Trevor_swfyc]

Re: A 4" and 4.5" hole.

Three things spring to mind.
1. Is the wood you are doing a trial cut on dry? damp wood no good.
2. Is the cutter new, never had a problem with a new hole cutter myself.
3. Are you maintaining the drill vertical, try putting some wood behind the ply so that the pilot hole maintains the hole cutter at 90 degrees to the ply.

Hope maybe at least 1 in 3 helps!

Regards Trevor



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[petery]

Re: A 4\" and 4.5\" hole.

I always use a jig saw with a narrow 'scrolling' blade - after drilling an initial 8mm hole. Most items you will want to fix will have a lip and a gasket that will hide any imperfections in your cutting

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[JimMcMillan]

Re: A 4\" and 4.5\" hole.

Jigsaw with narrow blade.Nae bother.

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[tr7v8]

Re: A 4\" and 4.5\" hole.

Best way is a "trepanning tool" looks like a drill with an arm & the arm has a pointed blade on it. Use at very slow speed and it makes quite neat holes.
Use em for dashboards inthe past.
[htm]http://www.europaspares.com/[/htm] and look for dashboards and go to the bottom.
DHC Adjustable Hole Cutter £ 16.45 + VAT


<hr width=100% size=1>Jim

Draco 2500

 

[chippie]

Re: A 4" and 4.5" hole.

If you decide to use the holesaw,Try to make sure it will contact the work evenly as you start so it doesnt want to track off in an odd direction, and then come in from the other side once the pilot drill has penetrated through. This prevents tearout on the back of the hole.
I have seen a jigsaw with soft felt glued to the base to prevent scratching used to good effect for this sort of job. While it is slower it is probably best to use a jigsaw with the pendulum action turned off or to a minimal setting to minimise tearing of the edges.

Good luck .

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[Strathglass]

Re: A 4\" and 4.5\" hole.

Use a holesaw with, as has been said, a fairly large slow drill.
Drill half way through from one side then drill from the other side. This saves splintering the surface of the ply. Alternatively a fine jigsaw blade can make a good job with care or, drill partially through with a hole saw then finish the cut with fine jig saw.
I would never sugest that a trepaning type cutter is used as it can be very dangerous to use.

I find that hole cutters will make a clean cut through ply, grp, and, with the correct lubrication, aluminium and even stainless.

Iain

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[Heckler]

Re: A 4\" and 4.5\" hole.

on something that big use a jig saw
stu

<hr width=100% size=1>http://www.beneteau-owners-association.org.uk

 

[rich]

Re: A 4\" and 4.5\" hole.

A Dremel is what you need, cuts well, but can get out of hand,and make i right mess.

<hr width=100% size=1>rich ) <A target="_blank" HREF=http://www.jersey-harbours.com>http://www.jersey-harbours.com</A>

 

[Gordonmc]

Re: A 4\" and 4.5\" hole.

There is a tool called a Rotozip which has more "oomph" than a Dremel. It uses a tungsten bit at high speed and unlikely as it sound it doesn't burn or melt grp.
I used one to make holes in bulkheads for heater ducts and it came into its own as some had to be cut in the confined space of a locker.
Ellen's shop used to sell them (B&Q)

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[vyv_cox]

Re: A 4\" and 4.5\" hole.

No shortage of folk advising you that you have bought the wrong kit, then.

For what it's worth, having installed my own heating throughout the boat, plus loudpeakers and various other bits of kit, I have drilled plenty of holes in wood, metal and GRP using 90 mm and 105 mm hole saws. Use a drill on low speed, you will certainly experience binding if the speed is too high. The advice on damp wood is very relevant, in this case rub a candle on the saw before drilling and you should overcome any snatching. Feed the load in gently. I am assuming that you have fitted the pilot drill and drilled its hole first?

So far as the other ideas are concerned, chain drilling is far inferior to a hole saw, it makes more mess and requires considerable effort to tidy up. Jig saws may be fine on the bench but my experience has always been that there is too much in the way on a boat and the saw needs a turning circle of 12 inches to cut a 4 inch hole.

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[JerryHawkins]

What type of hole saw?

I've used this type from ScrewFix to good effect. have a look at:

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=98028&id=16798

You'll need the arbor as well:

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=98028&id=12437

Cheers,

Jerry

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[rich]

Re: A 4\" and 4.5\" hole.

Rotozip is what i ment,,,sorry

<hr width=100% size=1>rich ) <A target="_blank" HREF=http://www.jersey-harbours.com>http://www.jersey-harbours.com</A>

 

[ditchcrawler]

Re: A 4\" and 4.5\" hole.

I have used the Roto Zip for several holes through various materials.It is first class.I paid £100 for mine about 2 yrs ago & now B&Q are doing them for under £50.Hard cheese.

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[tomg]

Thanks for all the advice

I will report back in a couple of weeks.

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