Diamond tools

Diamond tools are classified as either wet cutting or dry cutting, but they all work better wet. Wet is messy, dry is dusty!

Table of contents for this page. Introduction | Angle Grinder | Small Wet Saw | Cup Disk | Polished Concrete Floors.

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Introduction

Cutting wet, that is with a water hose either attached to the machine or having one spraying lightly on the machine and surface being cut is:-

• Better for the actual blade wear, so that it is cheaper than cutting dry.
• The reason for this is that the water cools the blade. There is an enormous amount of heat generated by the cutting action.
• The water produces a cement slurry that is very messy, clean it up while it is still wet, clean and clean it again.
• If that slurry dries it is almost as hard to get ride of as cement itself.
• Cutting wet does not produce dust, so for safety reasons in this respect it is better.
• The main safety concern with cutting wet is with electricity.
• You must use ELD safety boxes, see my power tool safety page for more on these.
• A lot of the newer machine have the safety device either built into the machine, or in the machine's own power cord.

Dry cutting is in general only done in short burst, to let the dust settle and to cool the blade.

• Because of the heat generated in the tool, generally the process is slower. More stops to let the thing cool off.
• There is an enormous amount of dust produced. Making it mandatory to use good quality dust masks and also eye protection.
• When grinding dry,I go for a rubber replaceable cartridge type dust mask, like a spray painting one.
• Don't use the paper throw away ones, as some of the grinding dust is very fine.
• I've seen guys take a paper mask off and have a rim of white around their nose.
• Dry cutting dust is also a killer for the machine itself. For example an angle grinder used by ceramic tilers sucks in the fine dust with the cooling air. This dust cuts out the bearings in the machine quick smart.
• The dry tools typically have slots designed to air cool the cutting surface.

The first thing learnt when I bought my large concrete saw was to take it easy, don't force the machine.

• As soon as you see sparks coming off the blade, slow down!
• This means that diamond is being used too quickly and is being wasted.
• There is an exception to this and that is when you are cutting through rebar.

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Angle Grinder

Below is my 235mm (9 1/4") Makita angle grinder with a diamond concrete saw blade in it.
I use it for cutting up to about 30mm deep in concrete. You can see the tide mark on the blade.
Any deeper cutting requires a lot of tedious work, for that I hire a larger machine.

Diamond tools - Makita 230 grinder with cutting blade

Used mostly for cutting Besser blocks,(hollow concrete) but it has also done a lot of service cutting masonry walls for chasing grooves for plumber or electrician.
Just about always done dry. This one looks like it would be more suited to wet cutting, as it does not have the expansion gullets (slots) and holes in the blade that are more typical for dry work.

This is the hard way of course, doing two cuts, and then removing the middle with a chipping hammer. You can buy a diamond blade that will cut the groove in on hit. Of course it is a specialist tool for large construction site.

Diamond tools can be used dry, just give them a rest quite often to help them cool down. You are grinding away at usually a very hard surface with another harder surface. that generates a lot of heat. Some guys say let them run for a while out of the cut, free spinning, to help the blade cool down. I don't bother.

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Small Wet Saw

Diamond tools - My small Makita 100mm wet saw.

My small 100mm wet saw has cut a few ceramic tiles, but not many as there are better tools for the job.

Where it shines is cutting compressed fibrous cement sheets (CCFC). Up to 12mm it cuts them like butter, the 16mm and over are a bit slower cutting but still easy. In the shot here I have screwed a piece of plywood to the base, to make it easy to use with a straight edge to cut straight lines. I used this set up to cut the 12mm CCFC sheets on these stairs.

This shot shows the arrow on the saw guard, which is the direction of rotation. Opposite to a normal (sidewinder) circular saw, It is a left hand thread, don't get trapped.

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Cup Disk

Diamond tools - A 180mm cup disk, comes in various patterns and grades of grit. This one is for quick removal of concrete bumps.

The 180mm cup disk above is also for the 235 grinder. Used for grinding back concrete floors and masonry walls for ceramic tile preparation.

I first used one of these while preparing a large floor for ceramic tiles. We hired a young guy with a large machine grinder to surface the floor and we trimmed around the edges and corners with one of these where the big machine could not get.

Floor grinding.

The young guy mentioned above was using a two head grinder, and he stopped every half hour to turn the diamond pads 180deg. in his big machine. He explained that it balanced the wear on the blades.

I guess he was right, but that was not the main reason.

• I later worked with a lot larger and more sophisticated grinder doing polished concrete floors.
• This machine had a switch to reverse the rotation of the cutting heads.
• After say half an hour cutting one way, I reverse the rotation, and straight away I can feel the machine cutting better.
• When it appears to be spinning easier and not biting the same, I reverse again, and so on.
• I guess what is happening is the switch in rotation exposes a different edge of the diamonds at each change.

Grinding floors with a big machine is nearly always done wet. The machine cuts better, but mainly there is no dust. An amount of water to keep a soupy slurry around the cutters seems to work well. You don't need lots of water.

If you are thinking of getting some grinding done, be prepared for a lot of mess. It takes a lot of cleaning to get rid of the slurry. I use a large squeegee to help to keep it under control.

Clean up while everything is still wet, again and again, as when that mud dries it is so fine that it is nearly as hard to shift as cement dust.

Keep in mind the usual safety rules,

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Concrete Counter Tops and Polished Concrete Floors.

This is a subject on it's own, and I will be writing a page on this later. I need to go back to a couple of jobs I have done and take some photos.

Once just for specialists, concrete surfacing tools were 100% air operated. Now small compact electric tools are available.

As far as the tools go, there are many on the market. I have used a large coarse diamond grinding cup disk like the one above, down to 100mm cups of varying grades to plastic faced type polishers.

The dedicated grinders have their own built in ELD protection and they feed the water in through the center hub of the disk.They are not cheap to buy and they are not cheap on consumables. You need quite a kit from course to fine wheels to make a reasonable job.

Floor grinding falls into two sections. Preparing a floor for another surface, like ceramic tiles, and grinding and polishing the concrete floor to an acceptable finish on it's own.

Check out this page, a submission from one of my readers, showing a really top finish on some polished concrete floors.

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