I just got a used Okamoto OMA-450 which I think is almost identical to the 350 but it is 6x18 instead of 6x12. I haven't got too far into it yet but I did push the start and stop buttons (no power applied). The start button does feel like a momentary contact button, but I think it does push in a set of contacts that are held in place while the button springs back. The stop button then releases the contacts and opens it's own contacts for redundancy to stop the grinder. I could be wrong but I'm pretty sure that is the way that start switch works.It would be very easy to check with an ohm meter without needing to take the switch apart.
I'll be using a VFD to run the one that I got but I may still use the original switch to send a start and stop command to the VFD.
I do have a question that I'm hoping someone here can answer. The oil pump is like nothing I've ever seen before, it is a solenoid valve with a spring loaded hollow plunger and check valve to pump the oil. The solenoid coil is bad on this pump so I ordered another pump but it has not arrived. My question is, shouldn't the power to the solenoid be pulsed in order for it to work? If you look at the diagram in post #1 it shows it connected to constant power which is how my OMA-450 is wired. I disassembled the one that I am replacing and the wires go straight to the coil, so it gets constant power.I'm assuming there must be something in the (plunger, check valve, and springs)that allow the plunger to cycle up and down with the coil under constant power. If anyone knows how they work please let me know.
Also to the OP Jericho, I don't have a manual for my grinder and I think your manual would be very close to being the right manual for my grinder.
If there is any way that I could get a copy please let me know, thanks.
Dwight