INIVATOR,
Replace the brushes on the Dremel Tool, vac out / clean the brush area, and run it off the machine for a little while giving them a
chance to seat. No / minimum sparking is good.
Now just for kicks, plug the dremel into the same outlet which has a TV or radio plugged into it. It'll make the picture fuzzy,
you'll get a lot of static on a radio. Post installation of new brushes try it again and you'll see a difference in the interference from the
Dremel. Now neatly coil the TV outlet wire, neatly wrapped around a tube and try again and see if there's additional improvement.
Take the Dremel and with it plugged into a different outlet , running ( hopefully not on the same circuit) and watch the interference. Now bring the running dremel near / around the TV and see what happens.
A coil provides an impedence to the path of the noise ( the coil / inductor can be made stronger depending on the core material ( in this case just air and the number of turns). Yes I would use shileded wire on the cables but if you don't have a problem leave them alone. You can get noise via the AC and you can also get noise traveling onto the DC switch cables since they act as a condutor of the noise.
The noise on the switch cables can really do a number since it going directly to maybe a board. Please note that i used "noise" as a general term to keep things simple.
RICH