On Sat, 11 Jan 2014 20:49:22 -0500, "Jim Wilkins"
wrote:


"DaveC" wrote in message
al-september.org...
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.

I don't remember any clear reasons for choosing one or the other from
my long-ago days designing industrial controls. IIRC at that power
level unless we needed 24V for other relays we'd go with a switch.
They can be had with two pushbuttons so you can slap the large red one
to shut it off.
http://community.woodmagazine.com/t5...v=mpbl-1&px=-1


But if you want an auto shutoff, low voltage control to a contactor
makes it easy.