Switch wiring on Rong Fu RF30/31 milling machines

[Deftone]

Coincidentally, the power switch on my 40 y.o. RF30 clone failed on Friday. It turned out that the switch contact for the neutral line were burned beyond salvage. The switch on my machine is a 3PST and was wired so that all three lines, load, neutral, and ground were switched. I moved the neutral line to the ground contacts and used the input terminal from the neutral contacts as a tie point for the ground wires. IMO, the ground line shouldn't be switched anyway. hopefully, now good for another forty years.

I tried cleaning up the contacts on the old switch. I sanded them flat and moved the unused center contacts to one of the outer positions. It worked a couple times but most often it just shut off again.

 

[RJSakowski]

It's not kosher to switch the ground
Probably a case of monkey see, monkey do engineering

It's certainly not best practice. However, I doubt that requirements were so stringent forty years ago. It wouldn't meet CE requirements nowadays. Looking further, the ground wire terminates in the motor capacitor housing where it is captured by the screw holding the cover. If the cover is removed, the ground connection is broken. I moved the ground connection to one of the mounting screws for the terminal block.

Also, the cable from the switch to the motor is router past the spindle spline and the insulation on the ground wire was worn through to bare copper. Had it been the load wire, it would have shorted out the machine or worse, if there was an open circuit on the ground, created a safety issue. I added a tie point to the interior and a wire tie to keep the cable clear of the spindle spline.

 

[Deftone]

Looks like the new one has the line and load terminal pairs on the long side of the switch instead of the short side like the old one

Yea, this new switch just won't fit. I re-wired the load side because the wires were too short to reach, but the switch itself is just too big to work in this application. I'm going to have to find a different, smaller switch then I'll likely have to fab a new mounting panel.

 

[markba633csi]

You might be able to find an exact match to the old one on Aliexpress but no guarantees