"DaveC" wrote in message
...

A friend (in USA) with a 220v, 1-phase horizontal bandsaw in his home
machine
shop wants to replace the 1/4 hp motor with 1/2 hp and rewire with an
auto-off switch (when the blade cuts through the metal).

I always default to using a 3-wire control with contactor, but he asks the
logical question: "Why?"

Other than the "If the power fails while cutting" answer (which he says
seems
of limited additional value on a saw with auto-stop feature) I wasn't very
convincing.

What are the arguments for using a contactor as opposed to a simple on-off
switch of equivalent rating?

Thanks.


The reason to use a contactor instead of just an on / off switch is that the
insides of the switch can get full of saw dust and turn on the saw with the
switch in the off position. I've seen this happen!
Regular AC switches are not sealed well enough, but you can buy sealed
switches with lower current ratings which is enough to engage the contactor.

Shaun.