Magnum heads. Is it safe?

NO MAGNETS. They will also cause the particles to stick to the head casting where the magnet attaches..Run a shop vaccum right next the "discharge" side of the cutter/stone you are using, and it will suck up almost all of the crud. Then use shop air to blow it off. Solvents will cause the stuff to run all over. Also, keep the intake flange as the lowest point, so the stuff rolls down and away from springs and assembly lube. Magnets and oil are an enemy in this case.