Hi.
Been using 120VAC power tools with 120VDC for a while; and probably will for a month or two more. Yesterday was the turn for a jigsaw for half an hour, and a circular saw for another half hour.

To prevent arcing in the on-switch contacts; what can be modified ? Replacing the switch with a proper or not one is a total robbery from parts vendor reaching an stupid $50

 

To prevent arcing in the on-switch contacts; what can be modified ?

Use diode:

 

Use diode:

But if you switch back at any time, remember to remove the diode !!!

 

Yes, would be better than the diode removing itself by releasing its smoke. Thanks.

 

That diode will provide no benefit at all for the arc when the switch is closed. That is when the motor current is greatest.