Also posted in the tool section:
I recently inherited a Elu mss810e reciprocating saw. The nameplate has it listed at 810w at 230V. I believe these were made by Black and Decker for the European market. It seems to work fine using a standard US 110v outlet. Does anyone seem any harm in running the saw this way?
Tools like this have universal motors, as opposed to induction motors. In any motor, current causes heat, too much heat, and the motor burns up.
In a universal motor, current is proportional to voltage and speed. If voltage is decreased, current will also decrease. As speed is decreased, current will increase, but with less effect that voltage. If you operate a saw like this at half of its nameplate voltage, and don't lug it down too much, it'll be OK. It just won't be able to cut as much as if it had proper voltage.
An induction motor (the kind with no brushes) will try to maintain a constant speed. If voltage goes down, current goes up. This type doesn't do well on reduced voltage.