I want to share my recent experience updating the wiring on an SP-20 motor to add ground. (Disclaimer: I am not an electrician although I consulted with an electrician.)
My press arrived with the power cord cut off where it exited the press. So, I needed to add a plug anyway and decided it would be best if it were grounded. First, I inspected the existing wiring for diameter which was 18AWG and this motor requires 3.2 amps and 115V. I purchased an extension cord that was 16/3 indicating three wires with a diameter of 16AWG. My electrician friend confirmed that I could go a bit larger, but not smaller in diameter.
I cut off the receptor end of the extension cord and ran it through the exiting conduit up to the junction box where the switch was. I then peeled away the plastic coating to expose the three internal wires: load, line (hot), and ground. Using spade connectors, I wired the load and line into the switch. The ground wire ran out a hole in the connector that attached the conduit to the junction box. From there I attached the ground wire to a bolt on the body of the press. I’ll soon update that connection with a ring connector for better security. Right now, the copper ground wire is just wrapped around the bolt and the nut was tightened to hold it in place.
The process was successful and my motor runs beautifully. The process of adding a ground was so much easier than I expected. If you try doing this yourself, it is important to make sure that the extension cord you buy is compatible with your motor’s amps, voltage, and wire diameter needs. I kept a fire extinguisher handy upon start up just in case, ’cause…I’m not an electrician.