Cutting square holes in walls

[JohnD]

I want to fit a wall safe, and need to cut a square hole in the inner leaf.

My inner walls are made of dense concrete tri-wall blocks (not lightweight foamed concrete). They have an 18mm sand and cement render with a skim of hard plaster.

For my first attempt, I used a small angle grinder to cut the outline and thought I could cut through the rest with a bolster and club hammer. However this made vast amounts of gritty dust and the bolster would not cut the slot like I wanted. I ended up drilling a line of 12mm holes and joined them up with the bolster, the blocks were still inclined to break rather than cut.

Is there a sensible way to do it? I believe there is a TCT chisel for an SDS drill, but I do not have one. I have a couple more to fit for guest use but have stopped due to the grit dust and time.

 

[Bylough]

For my money I would try a larger industrial 'angle grinder'- they have about a 10 inch blade- and a good vacumm. Fill the overcuts later.

 

[DAZB]

Go to your nearest HSS Hire shop or similar and ask for one of these....

http://www.hss.com/g/7131/Wall_Cutter__Low_Dust.html

It says it won't cut concrete but it means concrete slab and it will cope with blocks. You can also get a chain saw type cutter that cuts through breeze blocks and bricks but they are not listed.

 

[nstreet]

Go to your nearest HSS Hire shop or similar and ask for one of these....

http://www.hss.com/g/7131/Wall_Cutter__Low_Dust.html

It says it won't cut concrete but it means concrete slab and it will cope with blocks. You can also get a chain saw type cutter that cuts through breeze blocks and bricks but they are not listed.

I hope you're not putting that safe up too high, you need to be built like Arnie to use that thing, 13Kgs!!! at arms length, shoulder height, makes me sweat just thinking about it.

Only down side with chainsaw types is they are very very messy, most are water cooled as well so make sure you cover everything in sight or the missus will have a fit.