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Tony, that Furnass switch will be fine *as long as you don't switch under power* - it's rated for about 10A contact current (and unlike the Chinese offerings it's probably built to withstand higher than on the sticker), the issue that makes 'em drop the rating for DC use is arcing under load - AC (obviously) interrupts the current 120 times a second so an arc will quench and not erode the contacts, DC being constant will maintain the arc until the contacts separate far enough that it can no longer jump the gap - more so with an inductive load like motor windings (this is how a car's ignition coil operates, after all, producing thousands of volts and needing a condenser/capacitor on the points to absorb the voltage surge).
Big Industrial lathes with DC motors (Monach 10EE and the like) have enormous contactors with arc-blowout magnets to divert the arc and lengthen it to help quench it, often high-temperature insulating blades that cut the arc, and quite often resistor-capacitor "snubber" networks that handle the induced voltage spikes from the motor windings. It's quite normal to de-rate relays, switches and contactors by a factor of ten or more when using an AC-designed contacts to switch DC...
Just my ha'pennorth,
Dave H. (the other one)
Big Industrial lathes with DC motors (Monach 10EE and the like) have enormous contactors with arc-blowout magnets to divert the arc and lengthen it to help quench it, often high-temperature insulating blades that cut the arc, and quite often resistor-capacitor "snubber" networks that handle the induced voltage spikes from the motor windings. It's quite normal to de-rate relays, switches and contactors by a factor of ten or more when using an AC-designed contacts to switch DC...
Just my ha'pennorth,
Dave H. (the other one)