Right tool for the job ..?

I want to cut a channel up through some plaster skim to a light switch. Will just have to be deep enough to house 1.5mm T&E cable. What's the best way of doing it without cracking my plasterwork and taking half the skim layer down with it?

a
Reply to
al
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Various; eg you can hire a special tool with two parallel cutting discs which will do it. Or use an angle grinder with suitable cutting disc to cut the two slots? The mess will be indescribable though.

Alternatively, draw your two pencil lines from light switch to ceiling (or is it floor?) then work your way down the two lines with a good sharp bolster chisel, on the first pass just tapping it enough to break the plaster surface really. That should stop the whole lot coming down when you knock out the plaster between the two lines.

Takes a bit longer than using the angle grinder but not if you factor in hoovering up the mess later!

David

Reply to
Lobster

- Hire a cable channel cutter. A "stereo angle grinder", with a dust hood. Quick, neat channel and little mess.

- An angle grinder. Quick, reasonably neat channel, more mess.

- An SDS drill with a "spoon" chisel for chasing. IMHE these give more mess locally than an angle grinder, but don't throw fine dust around the room so much. Nice neat channel too, often better than the disks. The quickest of the lot too, because it takes the base of the channel out in a single pass.

- By hand, with a bolster chisel. Now this is the one to avoid, because it's by far the riskiest for damaging distant plaster.

I also like to use a negative ion generator when I'm cutting plaster or sanding floors. It makes the airborne fine dust settle out more quickly. Some people use water from a plant mister.

Reply to
Andy Dingley

I have an angle grinder ... a little on the large size perhaps (about half a metre long)! I could see myself accidentally cutting into the next room if I sneezed!! The former sounds excellent, but (as bloody usual) time is too much of a factor and tomorrow's Sunday.

Might be my only choice. I have some old wood chisels I could use then re-grind. Dunno how much punishment they'll take as the metal is obviously softer - but the only stone chisel I have is a 15mm cold chisel that's cut through enough heavy concrete to be about as sharp as my wit at the end of a Saturday night in a dodgy West-End bar!!

a
Reply to
al

Don't have an SDS drill at the mo ... one of those things I want to spend a bit of money on some day but haven't got around to yet. Possible catalyst will be my B&D hammer drill going up in smoke in final protest to the amount of abuse I level at it!

Yeah, I'm thinking that. Pain in the ass, but I think it's my only choice given that I need to do it in the next 24 hours. I believe I still have a bag of patching plaster somewhere or other .... ;o)

a
Reply to
al

It's not the fastest method but I have had a great deal of success simply drilling numerous holes along each side of the channel and then using a bolster chisel. The hold give the plaster somewhere to expand into and help stop cracks spreading.

Reply to
doozer

Andy makes some good very points about doing it with the least possible mess and/or violence. The less plaster you convert into dust, and the more gently you do it, the better.

If those are your priorities, then it's better to use a knife blade or a thin saw blade than a thicker angle grinder disc, and it's better to do it slowly by hand than quickly by machine.

You could make two parallel cuts with a Stanley knife blade, and then gently lever out the plaster. Start with a straight-edge to help scribe a straight line through the skim coat, and then you could possibly switch to an old hard-point saw or a large hacksaw blade.

Reply to
Ian White

How about a rotary file?

Reply to
Homer2911

Hi Andy

Can you elaborate on that Andy, it sounds interesting.

Dave

Reply to
David Lang

Sounds like a good idea to mix with the other methods. Thanks for the suggestions.

a
Reply to
al

Think I have an method building up here! Scribe with Stanley knife, drill out the middle, clean out with a chisel. Think it's about as good as I'll get without the right power tool!

a
Reply to
al

Could you get an undersized diamond disk that will fit the spindle but not stick out more than an inch or so past the casing?

Reply to
Rob Morley

In message , al writes

With a bit of luck all you will need to do is chase into the plaster layer, not into the brick/block underneath. If so then angle grinders, SDS drills etc. aren't necessary and will create a lot of unnecessary mess. And block is pretty easy channel by hand with chisel.

It also depends on the plaster. With the old plaster in my old house, you could score through it with the Stanley knife and then scrape the plaster out if was so badly adhered to the wall.

To start with I would score with the Stanley knife, then I would try with an cold chisel, old chisel, old screwdriver etc. to chisel/prise/ scrape the plaster out first, then move onto more heavy duty methods if necessary.

Reply to
chris French

In message , Rob Morley writes

What about using an angle grinder on low speed? I haven't tried it myself and await feed back from braver souls:-) I have a Bosch 125mm with speed control and guess you might have to watch overheating.

Also, what about the *gouge* attachment for non-rotating SDS drills?

regards

Reply to
Tim Lamb

Hmmm?, more mess than all the other solutions presented?, plus you'd eat a good number of bands in the process. Personally I'd go for the angle-grinder, missus holding the vac close by. Sunday?, hell, find a early-morning shed and pick up the cheapest.

Reply to
Mike Dodd

It's just one of those "mountain breeze" jobbies, or (being a skinflint geek) it's actually a diode multiplier wired up inside an old pregnant-plug case. Plug it in and it sprays negative ions and world peace into the room.

Fine plaster dust is so small and light it can practically ignore gravity. The stuff hangs around for hours. But stick a bit of charge on it though and it's rapidly attracted to a nearby earthed surface (picture frames, anaglypta wallpaper, unsealed woodwork, or any other hard-to clean material).

Reply to
Andy Dingley

A vac held right by the dust source works well ime, but you need to use a non-bag cleaner. Bags block almost instantly on building dust. So its either cyclone or those pricey water filter ones. I've not tried the cheap cloth filter bagless things, I imagine theyd have problems.

Trouble with angle grinders is they shower sparks, would likely knacker any plastic nozzle and hose, as well as being a poss fire risk. I'd use a long length of ali tubing. Be aware that concentrated suspensions of some types of dust in air can go BANG, so you dont want sparks in the dust canister.

NT

Reply to
bigcat

Only if you're grinding metal (steel specifically) surely.

Reply to
usenet

You'd be surprised how often you come across a piece of steel when channeling through plaster. Usually some long snapped off nail.

Reply to
Andrew Gabriel

Also be aware that a mate of mine did that when sanding down a fresh skim of plaster. He put the nozzle of a Dyson into the room and left it on for a while ....

.... a while later there was a bang. And funnily enough, no more Dyson! There is a limit to how much fine dust anything can suck!

a
Reply to
al

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