I've got a 100mm 1920s subfloor slab to break up and remove, about 2x4m. The nearby surrounding masonry is fragile and I really want to avoid a breaker if I can, as there's considerable concern about the risks of damage from vibration. But at the same time, it's a really hard one to cut - very dense, very solid, very hard. The flint in it only comes free little at a time, even when its mostly cut loose and with heavy tools; it's rock solid. On a test sample area for the engineer (180x250mm), my usual dry diamond 300mm concrete saw blade began to glow white hot, far beyond anything I've ever seen it do before (not unusual pressure on it). Trying again with water and a fresh blade didn't much help. I ended up working the opening that the blade did make, with a bolster, doing it piecemeal by hand.

As that isn't practical for the main cut, I'd like to go back to the concrete cutoff saw but this time better equipped with an appropriate blade better suited to the material.

Any suggestion of what kind of blade to look for, or a specific technique to use? I'm assuming there are such things, but as "flint concrete" isn't usually listed as a type of material on marketing material, it's hard to find which blades are appropriate or who makes decent ones. Especially as the blade design and hardness should generally be matched (inversely?) to the material.

Once the outline is cut, I'll be happier to break up the interior with the breaker, so it's mainly the outline I need this for, to isolate the inner area.

  • Merely red hot will tend to turn your diamonds into charcoal, after which they don't work very well for cutting. So watercooling (not haphazardly) seems essential, here. – Ecnerwal May 9 at 15:30
  • That made me smile! But what do I look for in a blade, for flint (apart from a water cooled tool?) – Stilez May 9 at 15:34

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