# Forum Home Renovation Concreting  How to cut a nice square hole in hard concrete?

## Watters

I have a demolition hammer which can make a hole in concrete easy as. However, the hole it creates is untidy. 
I would like to be able to do cuts in the concrete first before bringing out the demolition hammer to dig the concrete. 
I suppose it will be necessary to go down about 5cm with the cuts in order to stop the demolition hammer from breaking things lower down in a manner that will pull chunks from the nice cuts in the concrete. 
Would a diamond blade attached to something like the Bosch 150mm 18V Lithium-ion cordless saw do the job?
This would be dry cutting (wet saws are expensive).

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## r3nov8or

Please don't put a blade in a saw that it's not designed for. Although cordless is getting pretty good I'd go with 240v if possible. A 9" grinder with diamond blade would be good. Other options are wet saws, which are affordable hired if you have a bit to do. The larger the blade the closer you will be able to cut into the corners, without over cutting, if that's an issue.

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## Ozcar

> The larger the blade the closer you will be able to cut into the corners, without over cutting, if that's an issue.

  I don't get the reason for that - I would have thought you could get closer to the corner with a smaller blade? 
I would drill holes right through in each corner first anyway. 
I have found the "turbo" blades work quite well, but I have only used smaller sizes, up to 125mm diam.

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## Marc

What size square hole, what size concrete, for what purpose, what size jackhammer ...  :Smilie:

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## r3nov8or

> I don't get the reason for that - I would have thought you could get closer to the corner with a smaller blade? 
> I would drill holes right through in each corner first anyway.
>  ...

  See my picture. I guess rather than closer I meant "closer to the edge at some depth", if you get my meaning.  
Drilling the corners is a good idea

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## Ozcar

> See my picture. I guess rather than closer I meant "closer to the edge at some depth", if you get my meaning.  
> Drilling the corners is a good idea

  OK, got it - I think. Maybe it would be different if the diameter of the blade was bigger than the size of hole you wanted, but thinking about that makes my head hurt.

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## PlatypusGardens

Stihl concrete cutting chainsaw     
 Hook garden hose up and away you go.
Might be available at hire shops, not sure.   :Smilie:

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## Marc

You could cut a square hole in concrete rather easily with a concrete saw. Take ordinary concrete saw and water hose, and mark a square one meter by one meter. 
Start saw and cut square hole.
Chip the corners with a chisel and voila perfect square hole.
Another way:
Drill a 2 inch hole through the slab until you get to the dirt.
Insert dynamite in the hole, connect to battery to fuse and run.
After the dust settles, mark the edges of the hole with a string and cut straight in a square fashion with said concrete saw.
Square hole achieved.  :Smilie:

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## PlatypusGardens

Round cutting disc often leaves an overcut though            
also   *
A CHAINSAW THAT CUTS CONCRETE!!!!!!
HOW COOL IS THAT ?!?!?!?!?!!!! *     :Wink:

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## notvery

umm i have too ask Watters, do you have any soft concrete? and if you do make the hole there. 
also all these ideas are great unless the hole needs to be 20mm x 20mm.... how big is the hole.  
would it be easier to just smash a randomly made hole bigger than the required size, formwork, then pour more concrete around the edge... perfect square.

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## phild01

I would just drill 12mm holes in each corner and cut a neat square and then break it up.  No overcuts.

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## PlatypusGardens

But....concrete cutting chainsaw....

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## phild01

> But....concrete cutting chainsaw....

  Yeah, I know  :Redface:

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## Bloss

> Yeah, I know

  *WARNING* - *they are graphic images* of what chainsaw can do - a big problem is that unlike a knife cut a chainsaw (like a circular saw or grinder) removes flesh and is rough - so what is left has to be made to mate with a gap to be filled and no smooth edges. Worst I've seen is all toes removed - just behind the steel cap of a leather boot . . . and aside from the loss of all toes and the recovery he had to learn to stand and walk again, as toes, especially the big toe, play a critical part in that. A life of special shoes, continued pain and never really being able to do what he used to be able to do.  
7 Horrifying Chainsaw Injuries That Will Make You Cringe

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## Moondog55

Makes you realise that $1000- worth of PPE for a $300- chainsaw isn't exorbitant

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## pharmaboy2

One word, "chaps" 
and you you can take them clubbing in Darlinghurst as well

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## Marc

6 days later and several attempts at answering the unanswerable for lack of information (size, purpose) and no input from the OP.
Not even a Malaysian curry recipe from scratch can fix this.
I love Malaysian curry ... and Malaysian Laksa soup ... MMMMMMM 
What about fishing tales?

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