Your best bet so you don’t go burning shit down is if the panel has an extra slot or two, go ahead and wire in a separate breaker for the cutter. It’s not that hard to do, probably cost you $50-$60 in romex and breakers/outlets/etc…I imagin the main is probably a 200 amp service.
Find what the max draw of the cutter is. if’s it 20amp, wire in a 25amp breaker. house current type cutter and welders typically won’t draw more than 20amps.