"Steve Firth" wrote in message
.. .
wrote:

I have tried this with an angle grinder and I
find that the corners are breaking off and even one or two have
produced a smooth curved break about a third of the way in to the
cutting line.

The smooth curved break is a conchoidal fracture it's a characteristic
of ceramics and glasses to break in this way. The cause is that you are
trying to cut the tiles with an angle grinder. If you must do it using
an angle grinder then you need to a use a diamond disc, if you are
breaking the tiles as described witha diamond disc then it is a matter
of technique. You need to hold the disk vertical and to move it along
the length of the cut. Any twisting action (which is what I suspect is
happening) will cause a fracture as the disc bind in the cut and snaps
the tile.

From experience, even a diamond disk in an angle grinder produces poor
results, with the blade overheating (aka white-hot). A simple water-trough /
rotary diamond disk cutter (entry level = £30 from sheds) works wonders. For
full-sized straight cuts then a "contractors" (in Plasplug speak)
draw-and-snap style cutter is very effective. Tiled the kitchen floor, maybe
knackered one or two tiles learning how to use the tools. Tried plenty of
"cheap" work-arounds - non of which worked, in the end, spending a few quid
on half decent tools was worth every penny.

Regards