Does anybody have a schematic for the 3-position switch (Reverse-Off-Forward) for the South Bend Lathe? I can probably figure it out with a continuity meter. If so - I would greatly appreciate getting a scanned copy or pay for xerox copies and postage.
It's time to replace and upgrade the motor on it. It smokes in reverse.
Thinking about replacing it with at least a 1 HorsePower, maybe 1.5 horsepower motor. Any suggestions?
The most common types seem to be six terminal switches, eight terminal switches, and nine terminal switches.
Six seems to be common, and of these there are two types which look the same but are wired differently, the ones that cross the contacts closest to the handle to reverse, and the ones that rotate them from across to along the axis. If you are lucky, you'll have a schematic glued inside the cover of your switch.
For a single phase 220 motor, use the straight through terminals to operate the start winding, and the reversing terminals to reverse direction of the run windings. This allows you to avoid wiring "hot" straight through to the motor, where a short or bad ground would allow it to keep running even with the switch off. I got the idea for this from some previous RCM poster who I cannot properly credit without spending a lot of time digging back through archived posts.
For my lathe, I ended up with this for a 110/220 reversing motor, set for 220:
Where S is the start winding, with capacitor and centrifugal switch, M1 and M2 are the run windings, and L1 and L2 are the
220 lines coming in.
This is with a switch which operates this way:
Fwd Off Rev o--o o o o o | | o--o o o o o
o--o o o o--o
Note the jumper on the bottom left on the circuit above.
For the type of six-terminal switch that crosses the top two sets instead of "turning" them, the jumper would go from the left side of the bottom contacts to the right side of the middle set, and the output to the bottom of the run windings would come from the left of the middle set. Also note that my use of left-right- top-bottom are from the reference point of the schematic, and your switch may be mounted differently. Also note that the green safety ground isn't shown, but gets tied to the line, switchbox, and motor housing straight through, so you'll actually need 4 wires from the switch to the motor.
And lastly, your motor may be set up differently as well.
A wander through google groups looking for "metalworking drum switch" will get you a bunch of info for the variants.
One thing to check is the block which the wires hook to. Mine had the screws loosen up and the reverse position eat up the contacts with each activation until it quit all together. I have South Bends Original paper work for the various switches and how to wire them to a particle motor type. I'll fire up the scanner a see if it can pick up the details.
You can probably get then from industrial electrical suppliers, or from places like MSC or Grainger.
I picked up a spare from an eBay auction -- though it is of the format more often found on Bridgeport spindle motors (bar knob, instead of a lever shaft with a round knob at the end, but electrically, it still works the same.
Cutler-Hammer is one of the many brands out there, I think that Allen Bradley is another, or at least used to be.
But if you wanted to try your had at repairing the original switch, you might be able to machine a good terminal block to fit out of Delrin. The cover is a different matter, and perhaps a more serious one.