chasing electrical boxes

[alan_m]

In the past I've used the angle grinder to chase out electrical back boxes and have created an amazing amount of dust.

Today I tried a new method (for me) I purchased a couple of these for my multi-tool

and on the slowest speed cut the outline for two double 35mm back boxes and the channel for the wiring. This was into soft brick overlaid with

10mm of old fashioned (horse hair) plaster. A few bricks were more like cinder and were harder. While it did create some dust and a mask is advisable most of the dust just dropped to the ground rather than becoming mainly airborne. If doing the same again I may consider a spray of water to further contain any dust.

I also used the multi-tool to cut diagonal slots in the "waste" area of the back boxes. The material to be removed came out fairly easily with the use of a scutch chisel and lump hammer leaving very clean edges and corners.

Cutting the back box outline to a depth of 35mm+ probably took 10x longer than with a angle grinder but possibly saved 10x the time cleaning up the dust afterwards.

The blade does show signs of damage but probably could manage the same again before discarding.

On tip is to often move the blade out of the work to clear the debris.

[John Rumm]

Indeed, angle grinders and masonry inside are not to be recommended. If you must do it, then a wall chaser fitted with just one disk will do a very much better job of containing the dust.

I usually use similar carbide/diamond blades for sinking holes through tiles, but for "normal" walls (or once thought the tiles), I normally use a small SDS chisel to sink the perimeter to depth (marking that on the shaft with a ring of tape), then a wide SDS chisel to knock out the infill an plane down the back. Its a reasonable trade off of speed and mess.

[ARW]

Not compatible with DeWalt:-(

[R D S]

I've some to do, how long roughly?

(I get that my mileage may vary)

[alan_m]

Probably 30 minutes to cut 3 metres of outline to average depth of around 30mm (35mm+ for the back boxes). Possibly about the same to knock out the waste with the chisel. I wasn't particularly in a hurry and was attempting to achieve a neat result, which I did. I found some way into the job that repeatedly removing the blade from the slot (with the multi-tool still running) removed debris and was actually faster than trying to cut a longer part of the outline slot without withdrawing the blade. I was running the multi-tool at its slowest speed.

What I found helpful was to first make a shallow outline slot of maybe

5mm depth all around the area to be cut out before plunging in the tool to get a deeper slot

[Brian Gaff (Sofa]

I don't think this is a new idea though, but the equipment may be. When back in the 70s we had this house rewired they cut the edges round using some kind of hammer tool and then just gunged out the middle. That was a technical term used by the elecctrician.. grin. Brian

[jon]

I've done it quite successfully by hand with a cold chisel and hammer.

[nightjar]

You can buy box sinking tools for use with hammer drills that cut the hole exactly to the right shape for a single or a double gang wall box.

[Bob Eager]

Easier with an electrician's bolster!

[charles]

+1

[alan_m]

I'm always worried on this 100 year old house bashing the hell out of walls (brick lime mortar or lathe and plaster) for fear of creating more cracks, especially of the other side of the wall which has just been decorated.

[charles]

My BiL, when chasing out the party wall to take a cooker point hit rather too hard and the next door neighbours . looking through the hole said "Will you take your brick out of our bath."

[Dave Plowman (News]

Seen these and do wonder how well they work.

[ARW]

Not much use IMHO.

[alan_m]

A friend did similar with a cooker socket back box but on an internal wall. There wasn't a hole but a bulge in the other side of the wall where the plaster was held on only by the wall paper.

I found by cutting the outline grooves with a multi-tool first that I didn't need to hit the wall square on to remove the waste. With a long handled Srutch chisel I was hitting the brick sideways at an angle 30 degrees to the horizontal.

[alan_m]

They seem only to be demonstrated going into light soft aerated concrete (breeze) blocks

[Dave Plowman (News]

What I suspected. ;-)

[Dave Plowman (News]

You don't need anything clever with those.

[ARW]

It really does depend on the brick.

If it is red brick you get red brick dust and are left with nothing to fasten the back box to, if is black brick you are left with black brick dust and nothing to fasten the the back box to.

Other coloured bricks are available.

[Andrew]

"Perfect for chasing into plaster and some bricks for electric sockets/cables "

And only suitable for 'some' bricks, which means the soft ones that could be drilled, chopped out easily anyway.