Cutting Holes in 3/8"- 1/2" mild steel with no bevel

[MillersSteel]

Hello I am looking for any help as how to cut holes out of 3/8" - 1/2" mild steel without having to go back with a reamer bit and drilling the holes to size. Looking for any help or ideas as what to try ?

[BTA Plasma]

There are no absolute rules for good quality holes but a ratio of 1.5 time material thickness is your best hole at 60% of cut speed. You can drop dramatically to 10% at the expense of dross on the bottom. A good small hole is cut with a static torch height meaning it doesnt raise or lower in the cut. A perpendicular lead in with a small overcut and if under 100amps of power...a small arc lead out generally lead to very good holes

[weldguy]

Is your biggest issue a tapered cut, out of round, and/or just the incorrect size?

[MillersSteel]

My main issue is just a tapered hole. I have done the hole size a 1/16" bigger than the hole size I need but it depends on what is being cutting I cant always do that.

[weldguy]

Ok, so to combat the taper you want to take BTA's advice above and slow down your cut speed. The slower you go the more dross you will have but you can dramatically reduce the taper. Also be sure your traveling in the CCW direction and that your cut height is correct.

[SegoMan DeSigns]

Here is some more tips: