Hi Bob
I've not used them but 2 things come to mind.
The tools may become slightjy magnetised and grow a "beard" of swarf
You'll need to keep the doors closed or only work in aluminium or brass as the tool holders will attract iron/steel swarf and particles as well.
It's amazing how the stuff can spread itself!
Keith
Edited By Keith Long on 10/09/2013 14:20:22