Mark box outline+5mm on wall, put tape on SDS bit for depth required (or set depth bar on SDS drill), drill many holes to desired depth, use a scutch chisel and lump hammer to knock-out between holes, and a wide SDS chisel to "plane" the bottom of the hole flat.
I bought one many years ago, before I knew what I was doing. OK on light block but useless on brick or dense block, lots of dust too. I must put mine on feebay so someone else can find out how useless they are ;-)
I've only watched them being used. The chap doing the work was recessing into HD concrete blocks. It was a two-part job. First, he used a circular cutter, which looked a bit like the front end of a tunnel boring machine with a pilot drill in the centre, to cut a hole to the right depth. The pilot hole provided position for the sinker tool, which quickly converted the round hole to a square one. It seemed both quick and effective.
Similar thing happened in reverse for my son in law back in his bachelor days when the pub next door was having some alterations done. They kept him happy until the damage was fixed by passing pints to him through the hole.
ok on soft "cement foam blocks" or similar, not much cop any anything hard. IMLE.
True, but the main attraction is the right sized hole cut cleanly and fast. So they have a place if you need lots of cut-outs in the right kind of wall.
I've also used a sds drill with a 20mm hole cutter. Mark the centres of
8 holes (for a 2 gang box) and then drill the 8off 20mm holes to the required depth. The hole cutter plus the pilot drill hole removes much of the waste just leaving narrow pillars of brick that can easily removed with leverage or hitting with a chisel. Only the corners and edges then need to be cleaned up afterwards. I found with this technique that drilling all the pilot holes first was advisable.As I indicated before I'm very wary about hammering the internal walls in my house too hard as I'm sure that some of the 100 year old plaster is only held on by its own will power :) On walls where I have removed plaster in the past it came off very easily.
In message snipped-for-privacy@mid.individual.net>, at 14:21:30 on Sat, 10 Oct 2020, alan_m snipped-for-privacy@admac.myzen.co.uk> remarked:
We've just had our bathoom refurbished (I didn't do the work myself) and it turns out the old bath rim was set into a slot in the wall between the bathroom and a bedroom. With only wallpaper on the bedroom side.
They only work where the wall is breeze block or similar.
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