cutting concrete

[rob3780]

Hi
I need to cut a square hole in a garage floor (to concrete in a security ground anchor)

The hole needs to be 45cm square and about 40 cm deep.

Im not sure how deep the concrte on the garage floor goes but cant imaging it being 40cm.

Id like to cut out the hole as clean as possible, with out cracking the surrounding floor area.

So far iv elooked at breakers/air hammers thet you can rent out but i think these may crack the surrounding floor.

What other options do i have and what would be the best type of tool for such a job.

Would an angle grinder be capable of doing this?

 

[RF Lighting]

An angle grinder would be good for starting, but the blade will probably not allow you to get right through the floor.

You could use a stihl saw which would allow you to cut to about 4½" deep.

This was deep enough to cut through my garage floor.

Use the stihl saw to cut a square out, and also a series of criss cross inside the square.

If the concrete is deeper than this, you can drill a series of holes all the way around the hole, just inside the cut lines.

Then break out the square with a lump hammer and chisel, or a breaker. Something like an SDS drill with a chisel bit may suffice.

Start in the middle and work towards the edges.

 

[rob3780]

Hi,

thanks for the reply... i looked at a shtil saw...

Never used one of these before but it looks a pretty serious bit of kit.

How hard/easy are these things to use?

Thanks

 

[marshman]

Mark out the square on the floor then use a sds drill and drill your holes through the concrete along your lines as close together as you can get them,
then hit the square you want out with a sledge hammer, it will break along your drilled hole lines without breaking the rest of the floor,
use about a 16mm masonry bit.

 

[rob3780]

Thank marshman,

I read about doing this before somwhere.. seems like a good idea. Only thing is i went through loads of drill bits just trying to drill 4 20mm holes in the same floor. I just used masonary drill bits
Any specialist drill bits i can get hold of?

 

[Deleted member 105431]

Thank marshman,

I read about doing this before somwhere.. seems like a good idea. Only thing is i went through loads of drill bits just trying to drill 4 20mm holes in the same floor. I just used masonary drill bits
Any specialist drill bits i can get hold of?

buy some good quality COBALT drill bits.

 

[seaangler]

cobalt bits are for hard metal and stainless steel - not a lot of use on concrete
as previously suggested get a sds drill and quality bits to suit , if you cant get a sds drill then try bosch granite bits

 

[Hitachimad]

I would be inclined to cut a line an inch or so deep with a grinder, so you get a nice neat edge, then chain drill around the square just inside the cut.
A few across the middle to be able to break the lump will help get it out afterwards.
If you cant get hold of a grinder, drill and tidy up with a cold chisel

As siad, about 16 is a good size to go for.

You will need an SDS drill to be upto the job.
Drill bit wise, BoschS4, Dewalt Extereme, Irwin... most branded ones are good.
If you hiring, the hire shop will be able to supply them.

 

[Deleted member 105431]

cobalt bits are for hard metal and stainless steel - not a lot of use on concrete
as previously suggested get a sds drill and quality bits to suit , if you cant get a sds drill then try bosch granite bits

cobalt are great on masonry and concrete-I have a good set of masonry cobalt bits-not cheap though.

 

[mattylad]

Is this another job for the guy with the reciprocating saw?

 

[kevplumb]

you can hire a dimond tipped chainsaw eccelent fot cutting doorways out both skins at once