I found that the cordless saws like my Makita 4" 12volt make a nice clean cut and the blade spins so slow that the dust just drops to the floor without spraying all over the room. Prior to this I was using my 4" mini grinder with a "dust muzzle" attachment. This was a neat little plastic guard that hooks up to a 1 1/4" vacuum hose that sends most of the dust to your shop vac.the dust muzzle is at:
www.dustmuzzle.com Good luck,
Harold
