Q & A: Help! My Router Makes Sparks!
When I run my router I see lots of small, blue sparks
inside. Recently the sparks have grown larger. Is this OK?
Nope. Small sparks are normal, but large sparks are an
indication that your brushes are wearing short. That means
your router is running inefficiently. It’s time to remove the
brushes and possibly replace them.
The sparks are the electrical arcing of current from the
brushes to the motor’s commutator (the large cylinder inside
the housing). Large sparks mean the brushes are too short to
be adequately held tight to the commutator by their springs.
As a result, the motor has to work harder to make the electricity
jump the gap between the brushes and commutator.
Every router has two brushes.To service them,unplug the
router, remove the caps and pull out the brushes. If they are
chipped, cracked or shorter than 1/4 in., replace them with
ones made specifically for your router.To remove any carbon
dust, use an air compressor or a can of compressed air to blow
out the holes that house the brushes.Look into the holes with
a flashlight. If the commutator is pitted or severely worn, it will
need professional servicing. If the brushes are in good shape
put them back in the same holes, in the same orientation and
replace the caps. If you have installed new brushes, run your
router for two to three minutes to fully seat them.Your router
may “cough” and sputter a bit until it comes up to full speed,
but that’s normal.
This story originally appeared in American Woodworker February 2001, issue #85.