Well cold cutting wouldn't go over too well since 5160 will air harden somewhat. I'd suggest getting a metabo or a smaller hand grinder with a slicer wheel. I'll give you the airgas p/n's for the wheels. If you've never used them they are wonderful and every smith needs them in their toolbox.
the 4 1/2 X .040 64000806
the 6" 64000810
You can get these wheels at Lowes also.
I have a Milwaukee angle grinder that takes a 4 1/2" disk. I'm using a Diablo disk on it right now, and it's getting the job done, although I think I need to put a new disk on.
Have you used the Diablo disks before? If so, would you recommend the Metabo disks over the Diablo disks?