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I need to cut several tens of metres of 100mm x 100mm channels in hard (it's a C40 mix) concrete.

Some of these channels will be for electrical services, some for other services (mainly MDPE water pipes) and some cuts will simply be to assist in tidying up a bit of a scruffy concrete pour.

I have access to a machine that takes 12" (300mm / 305mm) discs and this will handle the depth that I need.

My question to you, the assembled experts in this forum, is: in your collected wisdom and experience, which brand / grade of disc will give me the most bang for my buck in terms of linear metres per pound cost?

Diamond of some form or other is an absolute given of course, but the chosen discs must also be dry cutting types.

I am happy to shell out for top notch discs if, in the collective hive mind experience, the price tag is warranted, but it is not always the case that the priciest product gives the best bang for one's buck.

I've never done any concrete cutting on this scale before, so I just don't know what to expect in terms of disc performance & longevity.

It may be for example that experience shows that a cheaper disc only cuts half the distance of concrete but works out more economical over time because it is only a third of the price.

I just don't know, but I am banking on some of you guys out there have plenty of experience and opinions to help guide my purchase decision.

I will be out on site and away from the forum until later this evening now, so please bear with me if you have questions that you need me to respond to. Although hopefully they will be few, as I have tried to cover the important stuff above.


sorry mate. ain't got a scoobie doo. i would get bob the builder to do it. better his lungs knackered than mine.
I don't envy you doing that job! Unfortunately I can't help. I bought some 230mm screwfix own brand diamond discs years and years ago and they lasted me absolutely aged cutting through marble and concrete and roof tiles but I don't know about the modern 305mm diamond discs sorry. Hopefully my reply will keep this bumped?

The Ghost

Are you intending to use a hand held cutter or one on wheels. Sounds like hire of one on wheels would be better for what you are describing.


I used quite cheap Erbauer ones from screwfix and was amazed how good they are they lasted longer than the marcrist ones I had before. Worth a punt for a couple of quid
Cutting is the easy part , Knocking the concrete out is going to be your difficulty . Criss cross cut along the channels and get yourself a heavy duty breaker .
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I used quite cheap Erbauer ones from screwfix and was amazed how good they are they lasted longer than the marcrist ones I had before. Worth a punt for a couple of quid
It sounds like this might be worth a try.

Worst case is that I start here and work my way up to Marcrist.

A couple of years ago I had to drill endless 22mm holes in brickwork and this is the experience that set me wondering just how much better the more expensive diamond cutters really were.
I use double 6 general purpose blades for most work, generally they perform pretty well. Definitely need to use water to keep dust down. Since you know its C40 concrete, might be worth giving Spectrum a ring to see which blade they recommend for that application. Stihl saw in a floor trolley would likely do the job.
As said, if you can sub it out to a specialist contractor, that might be your best bet.
You could do worse than to try Duro. They are experts in diamond cutting stuff. Their website is here. Duro Diamond Cutting Blades, Circular Saws, Grinders, Drill Bits & More -

Interestingly, the water is marketed as "dust suppression" rather than blade cooling. For the amount of cutting you are going to be doing, I would seriously consider using water. Otherwise, you will cover the neighbourhood!

My experience is more in diamond core drilling than disc cutting but the theory will be the same. Core drill diamond segments contain diamond crystals which are held together with a material called a "matrix". As you core the crystals wear. This causes them to come under stress. There is a limit that is reached that causes the matrix to "let go" of the crystal. Then the crystals that were buried underneath take over. The matrix material is specifically designed to hold onto the crystals for the optimum period in the material chosen. That's why it's important to choose the correct core drill (or in this case disc) for the material being drilled.
This "letting go" of the crystals and replenishing them with the buried ones is why wear occurs.
Now, in theory, if you don't use water excessive heat will be generated. Heat is what takes the edge off every cutting tool known to man and excessive heat will accelerate wear. So if you use water for it's primary function (dust suppression) then you have the added benefits of heat reduction, slower wear and longer tool life.

The diamond crystals are also of a specific shape and have a leading edge. This is why it's important to mount the wheel in the correct way, making sure the direction arrow on the blade corresponds with the one on the machine.

On a side note, Extreme heat build-up due to lack of cooling (or using the wrong diamond for the material in question) can cause segments to "glaze up". They become glossy and progress stops even though there appears to be plenty of segment left. This can usually be remedied by sending the tool through a more abrasive material (such as a breeze block) to re-expose the diamond crystals that have been glazed over. So, if you have a diamond core that you have been using in engineering brick that has stopped cutting - don't try it on hammer(!!), send it through a breeze block a couple of times and try again :)
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