Smallest "clean" hole size?

[Scratch]

I'm trying to use my plasma table to cut some nice clean holes. I can't seem to get the settings right.
I'm cutting 1/4" mild steel.
speed is 25 IPM,
using a TD 151
amperage set to 100 and using a 100A tip (per TD)

I can't seem to get a real nice 3/8" hole on front and back.

What's been your results?

[StealthDumpKits]

...I'm no expert, but that amperage and speed seems pretty high to me. Are you piercing at the center of the hole or on edge?

[Scratch]

I thought the amperage was pretty high, but I tried different tips, amperages and speeds and this combo pruduces the best hole that small.
It's nearly a perfect circle on the front, but on the back, I get someenough gouging that it looks bad.

The pierce starts 1/8" away from the edge, and arcs into the cut, and also arcs out of the cut 1/8".

I've heard Hypertherm has the fine cutting tips, but the only person I know with one, says he can't cut good clean holes with them either. But he doesn't really try either. He has no need for them.

[StealthDumpKits]

Try adjusting the air pressure. If that doesn't work, drill 'em.