Bolt circles not round

I’m having an issue cutting small bolt circles. If I try and cut 1/2 inch holes or less they come out somewhat oval. I cut out some 3 inch circles the other day and they came out perfect so I’m assuming my calibration is good. Everything else cuts nice as well. I’ve tried slowing my cut speed down and get the same result. Any help is appreciated!

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Plasma is famous for not cutting small holes properly round. It has to do with the fact that you are basically cutting a small electromagnet and this deflects the plasma arc inward as it cuts.

If you search the internet you’ll find a Crap ton of reference to this. Mostly the advices is “Cut em undersize and drill em out” (don’t forget to grind off the slag first or you’ll nuke your drill bit)

Really good consumables, really dry air and never cutting a hole smaller than the thickness of you material are all factors as well.

Hope this helps



I am having the same issue, other cuts are pretty good, I guess my mag drill will be getting some more use.

make sure your torch is perpendicular to the work piece. I have mine at a slight angle and it produced ovals

I too squared up my torch as close to perfect as I could get and that seemed to help. I also changed my machine settings to slow down the acceleration, that cleaned up all my cuts a lot. Bolt holes are still not perfect but much better. I watched a great video on YouTube about machine settings that I believe @Amp_Mechanic_JB posted. I followed his settings and that helped a ton.

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Steel Step Drill Set - 3 Piece, Titanium Nitride Step Drill Bits ( These are my go too I’ll be using them tomorrow on some bumper mounts.