The industry standard 608zz bearings have too much drag which can tend to rotate the tool housing when it is spinning and the bearings will run hot. This is the same symptom as the original bearings being worn out.....
John, I have discovered that you are correct. The bearings which I
purchased were the 608 ZZ but I find that they are still heating up.
I am planning to go back to the bearing store and see if they make a
better version of the 608ZZ. I also found out why this bearing is
readily available. The 608 is the standard bearing in inline skate
(roller blade) wheels!