Cutting neat rectangular recesses in brick

[Windmill]

Is there any way to do this, other than the use of masonry drills to make holes, followed by much work with mallet and chisel? (Which usually gives a result that's less than perfect.)

[John Rumm]

Angle grinder and finish off with a chisel in an SDS drill...

[Nightjar]

If you want to sink a hole for electrical back boxes, a back box sinker.

Colin Bignell

[harry]

Drill four holes at the corners first. Then angle grinder to link holes up. You could cut some additional slots across the centre too. Then hammer and chisel or a light electric breaker. Much easier to do when the slot has been cut.

[Stephen H]

I've done the angle grinder approach too. Only trouble is its quite dusty.....

I have 14 boxes to sink tomorrow across two rooms... breathing mask galore.

I've already marked up the room walls.

I'll use an angle grinder to cut a pair of parallel grooves from socket to ceiling. then use an SDS chisel to chase out the plaster between the two grooves.

As for box sinking, I SDS drill the corners, then use an angle grinder to do slots in the four sides. then SDS chisel it out.

[Steve Firth]

An alternative is to use an SDS mortar chisel. Although designed for removal of mortar they can be used to cut accurate rectangular holes in brickwork with less dust than an angle grinder.

Mark the outline of the box on the wall then use the mortar chisel to cut around the mark. The chisel has a number of diamond shaped teeth and it will cut very quickly and accurately. Cut as you would with an angle grinder within the outline and knock out the big lumps. You can then accurately sculpt with the mortar chisel and also dress the hole to have a flat back to the rectangle.

[Tim Watts]

On Friday 01 March 2013 19:42 Steve Firth wrote in uk.d-i-y:

I use a regular SDS drill with an 8-10mm bit in, with tape wrapped round at the required depth.

Mark box outline, drill round that and as many holes in between as possible, which takes not-a-lot-of-effort with an SDS.

Switch to SDS chisel and join the holes. Big advantage is you get a fairly even back to the hole and the dust is the heavy type (though the chisel can throw grit about). Less messy than any angle grinder or box sinker.

Box sinkers work well on celcon blocks and the like and are crap on brick.

[John Rumm]

Yup if doing an electrical back box holes in hard brick I find a combination of a 20mm SDS chisel for sinking a line round the perimeter, and then a 40mm one for chopping out the waste and planing down the back to get it roughly smooth and flat.

[Stephen H]

I have done 14 double gang rectangular recesses today with an SDS chisel.

Seven were in a downstairs room that had breeze block walls and plastered walls.

I had that chiseled out and the cable drop chases in 1 hour.

the other seven were in a upstairs room that has dry lining plasterboard on celcon blockwork.

I used a fein multimaster to cut 7 plasterboard rectangles and then SDS chiseled the blockwork for the back boxes. Another hour....

So that's 14 double gang boxes sunk into the walls and 7 cable drops chiseled out of the plastering.....

And not a grazed knuckle or a lump hammered thumb/finger in sight....

SDS chisels ROCKS....

Although I dressed the back of the rectangles as best as I could, I used "Sticks like 5h1t" to act as a filler between the bricks and the metal boxes, so with three rawlplugs and three screws, the back boxes will not wobble and can be set to the right depth relative to the plasterwork.

Stephen

[F Murtz]

Multi tool with carbide cutter.

[John Rumm]

For box sinking inside, skip the AG and do it all with the SDS - far less dust (unless you have a proper wall chasing AG with collection)

[Windmill]

Might be difficult to get the angle grinder close enough to the corners, but it's certainly an improvement on chisel alone. I suppose I'll need to experiment.

[Windmill]

Thanks; I do have a large, clunky, cheap SDS drill bought for the sole purpose of drilling through almost a metre of masonry, but had forgotten that it also came with chisel bits. Hopefully that will be better than hand chiselling.

[Windmill]

Probably too expensive for a single use, but useful to know that there are such things, just in case the world changes (again).

[Windmill]

Don't think the SDS chisels which (I now remember) came with my drill have diamond-shaped teeth, but maybe what's there will serve.

Thank you for the description.

[Windmill]

I only need to do this at long intervals, and after a year or two tend to forget how difficult it is with just masonry drill followed by hammer and chisel.

Maybe with an SDS chisel I'll be quicker/better.

Crap totally, or just slow? I've noticed that 100 year old bricks can have some very hard areas, plus some parts that are relatively soft.

[Windmill]

Hadn't thought of that before.

I bought a cheap one from LIDL intending to use it on wood, but maybe it included a blade for masonry. ISTR someone recently posted the name of a place which sold blades for various models; I'll need to check the prices.

Are there any pictures showing how one might use the tool for this purpose?

[F Murtz]

Don't know of any pictures But these things are not violent like angle grinders so just point it at the wall and press gently,if you find the right blade.(experiment with it)

[Tim Watts]

Very slow and makes an incredible amou t of dust

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[Steve Firth]

Are there no shops where you live?

For reference this is the sort of chisel that I mean:

You're welcome.