Greeting gang, I have an old dynamotor chassis I want to build a power supply on for an ARC 5 transmitter , I don't have to do too much cutting ,but there is a opening I need to enlarge about an inch or so to accommodate the wires for the power transformer . Any thoughts on proper tools ? I don't have any cutting wheels yet ,but that's the direction I'm going and or filing . Will chassis punches work on steel if it isn't too heavy gauge ?

Thank you

Yes, unless claimed not for steel... 1/8" mild steel is about max, lubricate well both cutting surfaces and the threads.

They make metal hole saws. That metal is likely too thick for a nibbler, IIRC. Sometimes a cone reamer will work well. They make some large ones for pipe up to 2" that I have seen.

Do NOT use a fly cutter with a hand drill. (:oops: ).
I have used an air die grinder also.
Often, your local full service welding or machine shop has a punch capability.
(Talk to them. You might be able to get it done for a 6 pk. left by their back door.)

Might try a Dremel using the thicker cut-off wheel.

step drill

Yep! Those do a good job, use plenty of lube too. Some step bits are in metric others fraction. They can grab the work so use clamps.

+1 on the Greenlee chassis punches and the old time pipe reamer. I have an old vintage pipe reamer that will ream a hole from 1/4" up to 4 inches.

Allow for extra room to add a grommet to protect the wires.

And work gloves! Ask me how I know to do this...