I am trying to figure out if there is something wrong with my 660 (new) or if this is normal. The shaft gets extremely hot, even when not routing (not in contact with anything but running). After about 5 minutes it gets really warm to the touch and after about 10 it if hot. If normal I will just ignore it. At first I thought it was maybe because I was using a speed control but tried it at full power and it still gets hot. Plenty of air blowing out the bottom (warm air after a while).
Hard to quantify but yes they get hot.
Happens to mine. The shaft/collet get very warm to the touch even when it is under no load. I grew to ignore it 
Yep, electric motors get hot. The shaft down the middle is just a heat sink, so it will get hot as well. Mine has run for 20 hours continuously, with no effects that I can find, other than a crap ton of graphite dust from the brushes.
Ok, thanks. I wont worry then. I also noticed the graphite dust towards the end and got scared. This was the first run of it.
You’ll definitely get graphite dust if it’s the first run. It has to wear in the brushes. I think they run them at the factory, but only long enough to see that it works.
Was just running my 660 on the table to test a part and in under five minutes the shaft was very warm. Heat has not been a problem with how the Dewalt 660 any any of the cuts I have done over five hours.