wrote in message
oups.com...
Every time I want to open up a hole, I reach for my Air Grinder or
Dremil and use a 'stone' grinding bit. But it never seems to do much
and wears out quickly.

I was recently at a Motorbike exhibition and there was a tool stand,
which had a range of 'bits' which were completely metal! They came in
all shapes and sizes (balls, cones, cylinders etc) and had various
patterns sliced into them. Some had horizontal and vertical slots cut
in them, leaving a load of sharp edges, and some had a 'cork-screw'
like pattern cut around the outside.

Since then I have been looking for 'bits' like this and can't find them
anywhere. None of my tool catalogues show anything remotely similar.
Does anyone know what these tools are called?

Are they designed for 'grinding' in general, or did I misunderstand
their use?

Any info would be appreciated

Carbide burrs used for cylinder head porting and general metal removal. I
have dozens of them in my head shop and any major engineering tool supplier
would be able to sell you some.
--
Dave Baker