On Thu, 25 Sep 2008 16:38:45 +0100, "mark"
wrote:

On a new diamond blade you can see the diamonds zone. It is something like
10mm deep on a 9" disc.
They 'wear out' when this section has gone.

Hello again,

Sorry to reply to the post so late. The disc that I was concerned
about was Toolstation code 83764. I think someone recommended
something like code 21172, which has "slots" in the disc. I originally
chose the continuous-edge disc rather than a slotted one because the
blurb said it gave a smoother cut. Is a slotted disc better or doesn't
it make any difference?

The photo of 83764 shows the diamond edge as a thick silver stripe
around the circumference. I bought a new one and found that mine had
worn to a quarter of its thickness: there was probably only four or
five millimetres left. Would you change it at that point or would you
continue to use it until its all gone?

I figured since I had a new shiny disc, I would use that instead. I
had tried two angle grinders (Bosch blue 4 and 9 inch) using their
respective versions of the same blade and both are struggling to cut
this concrete. In fact the 4 inch almost stalled at one point. The
discs have got hot and there are black patches on one or two points
where the disc has overheated. Does this mean the discs are fried?

I need to channel for some 15mm pipes to the radiator. I tried my Aldi
all chaser and that can't cope either. It's a concrete floor in a
1970's house. What's going wrong?

Thanks,
Stephen.