Perhaps temporarily remove your collection nozzle and replace it with a
piece of cardboard faced with a sheet of witness paper (plain white paper)
suitably mounted to the wheel shroud and perpendicular to the magnetic
chuck. If this detects the particle strikes satisfactorily, grind a variety
of materials, dress the wheel, etc with it in place. Then shape the intake
of a new collection nozzle to encompass the accumulated particle spray
pattern that has formed on the witness paper.

David Merrill

"Ned Simmons" wrote in message
...
On Sun, 21 Jun 2009 01:04:47 +0100, Mark Rand
wrote:

If you have to stick with running dry, the main thing is to put the hood
where
the grit is going to be thrown into it already, without any help from the
suction. The grit is coming off at 60mph. Anything you do with airflow is
only
going to help once the grit is already in the pipe. So have a hood that
has
steep enough angles that the grit won't bounce out and have it located so
that
it's almost touching the work.

That's what I've tried to do so far, but I underestimated the spread
of the rooster tail of dust. I guess I'll make some quick and dirty
pickups of PVC and cardboard to see how much improvement I can make.

--
Ned Simmons