"Derek Hartzell" wrote in message
...
It is torque, not horsepower that cuts the wood.

Part true/Part False. Both torque and horsepower cut wood. For a given
horsepower there is a certain speed where you can take a certain depth of
cut with a certain tool in a certain type of wood. A 3 horsepower can
take
basically 3 times greater cut than a 1 horsepower if both are running the
same speed. Another factor is that having excess horsepower helps keep
the
speed of cut consistent, which improves the quality of the cut.

Horsepower = Torque x RPM / 5252


With electronic variable speed you lose torque at low speeds, this is
why
the bigger lathes have 3 hp motors, to make up for the lost torque.

False. When you turn down the speed, you are turning down the horsepower.
So a high horsepower motor allows you to have good horsepower through a
wide
range of speeds. If the rated speed of a motor is 1750 rpm, then you
will
get the full horsepower rating there (for example a 3 horsepower motor
will
deliver 3 hp). At 875 rpm motor speed, the motor gives 1 1/2 hp. At 437
rpm, you only get 3/4 hp.

Thank you Derek,
As you turn down the speed, the horsepower decreases linearly from your
example, and thus the torque is constant from the above equation. If I
understand all this right, I can take the same heavy cut (amount of material
removed per revolution) at full speed or 1/4 speed, I just have to adjust
how fast I move the tool along the tool rest. Just to be clear, I'm still
talking about electronic speed control here.

Thanks
Martin