On Sun, 3 Apr 2005 19:14:26 +0100, "Michael Chare"
wrote:

Can anyone explain what the difference in the disks actually is

Depends on the quality. For "market stall" disks, they may indeed be
the same thing.

Stone is generally harder grains in a soft matrix, and these grains
are harder than steel. So stone disks are an abrasive that is hard
enough to cut effectively. Metals, even steel, will tend to "load up"
an abrasive and so the disk must wear fast enough to expose new
abrasive.

For 4 1/2" domestic grinders, there's no real risk in using the wrong
one. But metal disks will cut stone poorly and wear out rapidly, stone
disks on metal will clog and then cut poorly.

Personally I very rarely use metal disks these days - almost entirely
flapdisks now. The blue pro-cut coated ones from CSM Abrasives are
worth the extra money too.