# Forum Home Renovation Concreting  Cutting concrete with Angle Grinder?

## montiee

I need to cut out some concrete from a slab. No idea how thick the slab is. Measurements for the cut are 500mmx 600mm so it's pretty small. The slab is quite old (built same time as the house, I'm guessing 1950's or so and in the shed. 
 I know a wet saw would be the best way to go but was wondering if I could get away with a large angle grinder and what types of discs I'd need and roughtly what they'd cost. How successful will I be going with this option :lol: ? 
Cheers! 
PS:
Just curious, has anyone hired a wet saw in Sydney and what would be the going rate just out of interest.. I probably prefer the angle grinder because for the cost I'll be able to add a large angle grinder to my tool collection for the price of the wet saw hire I guess.

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## Batpig

Dear Montiee, 
An Angle Grinder - large or small - with the correct Disk, will most certainly do the job, but before you race off and buy a new 9" Grinder, do you happen to already own a Circular Saw - either large or small? 
I ask this because a Circular Saw has the advantage over a Grinder of having a Baseplate, and this really helps to keep your cut straight and uniform. And the other thing is, I have found my 9" Grinder to be terribly un-versatile; too big and heavy for comfortable grinding (especially before a Grinding Disk has "trued-up" - the vibrations beforehand are indescribable and can literally lead to the screws vibrating off and the thing falling apart), and too powerful for safe cutting (a semi-stationary Cut-Off machine is a much safer proposition for large cuts that a 4" or 5" Grinder can't handle). I would therefore say to you, don't set your heart on buying a 9" Grinder. Instead, if you already have a 4" or 5" Grinder, go out and buy a "Super-Turbo" Disk that will suit the Grinder, including it's Arbor size: http://www.tradetools.com.au/ProdVie...Product=TTSUP5
As you can see, they're cheap enough...
Now, if you don't already have a small Grinder, I would go out and instead of buying any sort of Grinder - large or small - I would buy myself a small Circular Saw, along with a 7" Super-Turbo Disk. You may also have to buy a little "Arbor Bush" or "Adaptor" to get the blade to sit on the Saw... 
Wet Saws really come into their own for either internal cuts where there would otherwise be a lot of dust, or big, long outdoor cuts where the blade could start to overheat. But for a little outdoor cut, a Grinder or a Circ will do the job. Doesn't have to be a terribly deep cut either - an inch or so will be enough to give the concrete somewhere to stop breaking off when you start hitting it with the cheap Rotary Hammer. Another cut diagonally into any corners will help to break the concrete out more easily... 
Best Of Luck,
Batpig.

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## fubar

gday did the same thing few years back but i went and bought a gmc 7 1/4" saw fitted stone disc to itused a lemonade bottle for water supply( but found it wasnt necessary)and cut through 4" patio slab no worries and the saw still works cost me $70 all up  just let the disc do the work didnt push too hard and have used it on cement sheeting no worries

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## Compleat Amateu

With all respect, I reckon you are outta ya cotton-pickin minds .... there are some jobs for a wet saw and this is one of them.  Esp if there is reo in the slab. 
I know it's a pain in the **** to:
1.  Drive to kennards (or whoever) and pick it up;
2.  Do the job and get mud (nice word) everywhere;
3.  Return same to kennards (or whoever). 
But step 2 will take you about 15 minutes once set up, beats the hell out of dust, blades etc if you use a wet saw.  IMO, a no-brainer. 
Kennards have a website that quotes $$$$ for their tools, that'll give you a quick idea of bucks. 
Oh, and remember to cut the block into littler blocks for removal ..... I didn't!

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## montiee

Thanks fellas. I do have a GMC circular saw. 
 The mid sized one which should probably be enough. I have to head into the shed and checkout the size. Never thought about using it but you are right the baseplate would make it all easy. I just assumed I could only get discs to work for grinders. 
Does anyone konw if I need offsets/adaptors to use these blades with a GMC circular saw?  
For ~$20 a disk it's alot cheaper than I was thinking it would be which is always good  :Wink:  
I know the wet saw is the rolls and would make my job easy however for the cost and the size of the cut I want to do I don't think it's really worth it. Trip, time and money. If I was cutting a decent size of slab I'd probably dish out but for 500x600 sounds like overkill. Basically it's be one plunge down of the saw I'd imagine :lol:

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## fubar

my experience the arbor size was the same so no probs

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## montiee

Anyone want to let me know what the diff between a segmented blade saw and the full variety, apart from the fact that one is segmented the other isn't :lol:. Just curious..

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## Batpig

Dear Montiee,  

> Anyone want to let me know what the diff between a segmented blade saw and the full variety, apart from the fact that one is segmented the other isn't :lol:. Just curious..

  Bugger curiosity! That's a damned good question in it's own right, and would make for a very good thread in the "Handtools - Powered" subforum over at the Woodworking Forums...
In effect, you're wondering what the difference is between the four types of disk shown in the photos below: 
1) Continuous Rim:
Obviously the most gentle method of cutting since there are effectively no "teeth". Therefore best for high-quality cutting of Ceramic Tiles - WET or DRY. The Pro's use them DRY on small Angle Grinders to cut notches and stuff out of Ceramic Tiles, but you also see them on all of the powered Tile Saws that run WET. The penalty of this gentle cutting, however, is that they are too slow for thicker material, which is why you instead see the Segmented-type disks in the dedicated WET Stationary Brick Saws...
Wouldn't even bother trying to use a Continuous to cut Concrete with. Might be okay going through the Mortar Bedding under some tiles on the Bathroom floor, but Concrete is a different kettle of fish... 
2) Segmented:
As alluded to above, these are more aggressive than the Continuous Rim, due to the notches that effectively act the way that Teeth and Gullets do in normal saw blades for timber. You see the Segmented a lot on Wet Saws for cutting concrete - either Handheld or Walk-Behind - as well as on Stationary Brick Saws that run WET. Can't see why you couldn't cut Concrete DRY with them, however... 
3) & 4): Turbo and Super-Turbo:
Performance and application probably similar, but Turbo is probably a little easier to manufacture than Super-Turbo, since the parent disk is just flat on the Turbo, compared to contoured on the Super. The contours on the Super's body, however, might help with cooling and clearing of dust.
I've used the same Super-Turbo disk successfully DRY on my both my 9" Grinder, and my brother's 9.25" Circ for full-depth cutting of concrete, as well as some very neat DRY cutting through Ceramic Tiles in place on a Mortar Bed.
I've also got a couple of 5" Turbo's (as in non-Super) that have coped with everything I have thrown at them when used DRY in my 5" Grinder, or WET when mounted in my little hand-held 5" Wet-Saw... 
That's my 2c worth. Now Montiee, if you do happen to do some searching over at at "Handtools - Powered" in the Woodwork Forums, and you find a good thread on the subject, please post the link back here... :2thumbsup:  
Now, perhaps some kindly ultra-Pro will step up to the Pitcher's Plate and give us some "Good Oil" on the subject... :Redface:  
Best Wishes,
Batpig.

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## montiee

Appreciate the info batpig!

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## Kaptan

Hey Montiee, I just removed a section of the concrete path around my place to install a rainwater tank.
Thought about the wet-saw idea, but considered it to be over-kill.
Went to the local hire yard and got a 9"angle grinder with a dry diamond blade.
Cut 2x 2m lengths, and 6x 800mm across like it was butter. 
Just pick a windy day, and wear the right safety gear.   :Wink 1:

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## barney118

Montiee, 
Using the right tool for the job is always the correct answer. Using a demolition saw at hire company worth its weight in gold. ($~45 half day ) depending on concrete an idea the concrete will be either 100mm deep or bigger most likely it will have steel reinforcement half way down so you need to get through this too. Not sure of what you are trying to do but they are also bulky and cant really edge cut to a wall that well (except putting on an angle) and use a hose with a sprinlke allows the dust to be turned into soup don't use the water too fast otherwise you will have a swim. 
On the other side SAFETY cant be reinforced enough a 9" gringer are ANGRY and have plenty of tourque enough to rip out or your hands and possible do bad things if you have a lock on the switch. 
Otherwise some point in time here you will have to call upon the steel bar to chip away at some time or this is enough to do the job by itself.  
Start with the steel bar and listen for the sound to get a feel if it is solid or not, the downside to using the bar is its not neat but sometimes its the only one to do the job. All concrete needs is a stress point to crack along but you might do more damage eg cracks further into the slab (most likely surface anyway but if upstairs/structural dont even thick about it).

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## kombiman

Many ways to skin a cat.... 
For my $$$ I would go the wet saw from the hire shop.  If it has reo, thick bits etc the wet saw on the dolly will work awesome, especially safe compared to circular saws and 9" grinders. 
I dont have fingers to spare. 
I have done both and next time I need a decent cut through concrete the hire wet saw gets it!

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## Compleat Amateu

Good discussion gentlemen, 
Particularly like BatPig's learned discursion on blade types - I've printed that for the next angle grinder job - and I'd summarise the posts as follows:
1. Can use angle grinder - with the right blade - up to 100mm (?) concrete, not too much steel as one would expect in 100mm of concrete;
2. Over 100mm of concrete, or a fair amount of steel (and we haven't defined what a fair amount is), then a wet saw is the go;
3.  The tool will vary a bit with the economics and "acquisition difficulty" - if a hire place is close by, one would be more likely to use a wet saw than if it was 100km away. 
Appreciate your inputs, always learning

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## PlasterPro

be carefull of 9" grinder I lernt he hard way, they bite.3 months off work.
can`t even stand the noise of them now and have to get someone in to do any concrete cuts.

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## Jaydon Landon

When cutting concrete,with a concrete cutting blade is water supposed to be applied to the concrete......?can anyone give me a clear suggestion...thanks

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## dastrix

> When cutting concrete,with a concrete cutting blade is water supposed to be applied to the concrete......?can anyone give me a clear suggestion...thanks

  I would imagine so, I used a rather large concrete saw with a diamond blade that ate through my 100mm slab like butter - even the reo. Get the water on there (enough to keep the blade cool) to preserve the life of the diamonds..

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## autogenous

You need a quick cut with a clutch as grinders can grab, flick up and cut your neck in half. 
Its a dangerous exercise to be sure to wear every possible piece of safety gear recommended. 
Too many blokes have been put in the ground doin this type of work. Its worth having someone do it for you. Itll probably cost $200 bucks to have a bloke do it..

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## buts

Hello,
I need to cut off an extra concrete on one side of the concrete path (100 mm thick) left by contractors. I can ask them to do it only after 90 days maintenance period (new house). I have Makita 235mm circular saw and was thinking to buy TTSUP7 super turbo 180 mm diamond blade and use it. Will it work ? Do I need an "adapter"/"Arbor bush"  for the blade ? If yes, could anyone refer me to the adapter specs and some place to buy ?

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## kombiman

> Hello,
> I need to cut off an extra concrete on one side of the concrete path (100 mm thick) left by contractors. I can ask them to do it only after 90 days maintenance period (new house). I have Makita 235mm circular saw and was thinking to buy TTSUP7 super turbo 180 mm diamond blade and use it. Will it work ? Do I need an "adapter"/"Arbor bush"  for the blade ? If yes, could anyone refer me to the adapter specs and some place to buy ?

  
If you can get them to do it, even after 90 days, do it. 
If you need to do it hire the concrete wet saw. 
If you won't/can't You can get the 235mm blades with the correct hole size.  If you use a smaller blade it won't cut as deep. 
Check for tool shops is your area.  Glenfords/trade tools etc.

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