On 2009-09-01, GeoLane at PTD dot NET GeoLane wrote:

In addition to the old gearbox speed changer, speed can also be varied
with a pot (0-60 Hz).


I have a TECO FM-50 for a 2HP Bridgeport. A pot and on-off switches
in a separate box would be a lot more convenient. What are typical
specs for a potentiometer for one of these? Something I could pick up
at Radio Shack or do I need to order on line? Under what section of
the manual would you go looking for specs if it's something that
varies by manufacturer and model? I only read enough of the manual to
get my mill up and running so I could play with it. Now that I've had
it for several months, it's time to make improvements.

Your VFD manual does not seem to say what the rating for the pot
should be. Mine said, IIRC, that it should be between 1k and 10k. I
used a 1k pot because I have a few of those. 5k should work well. You
can call Teco and ask to be sure.

If you want a pot and an on-off switch, then you can buy a pot with a
built in switch, those are widely available. They have two contacts
for a switch and three for a pot, usually they click and turn off when
fully turned counterclockwise. So you can wire that switch to turn off
the current when the switch is off, and turn on and ramp up the
frequency as you turn the knob clockwise.

Now if you want a pot and a forward/off/reverse switch, then you need
to have them separately, pretty much.

It is really up to you as to what you want, for instance whether you
want to power tap on the mill.

Radio Shack could be pricey, but the easiest option of all. Most
likely you need a 5k pot.

i