I am on my soapbox again - The steps per inch checkout pretty close. What does this mean
Either they are correct - to the number you have calculated , or they are wrong. Please yourself. Your steps per inch will be a simple round number e.g. mine is 60,000 - not 60023 or 59395. Claculate your steps per unit and put them in.
Motor - probably 200 steps, microsteps - depending on drive - 4,8,10 or 16. gearing down motor to leadscrew 1 (straight drive), 2,3, etc and finally leadscrew pitch - mine is 10 to 1 inch - multiply together and get a round number. Do not measure, jog up and down or anything else. The calculated number is your steps per unit and cannot be altered.
If you are to do "perfect" circles then you will need backlash compensation engaged. You may have none - lucky you - but there is some there, otherwise your machine would seize up. In describing a circle, all axis change direction once and probably twice - depending where on the circle you start, and if you have not compensated for backlash, however small, you will not get a "perfect" circle.
Check your machine over by making sure there is no obvious slop and then simply zero the DRO and type in the MDI line GOX1 to get rid of backlash.Make sure backlash compensation is not on Set up a DTI or a pair of digital calipers - I use digital calipers - take a reading and zero them. In the MDI line type G0X2 then G0X1. The axis should move an inch and move back. Measure with the digital caliper again - this should be zero, but it will not be - and the figure shown is the backlash - that amount of the inch the axis did not move, whilst the gears and everything were swapping round to push the other way.
You can repeat it if you wish and take an average, but I normally put the backlash in the computer and turn it on and repeat what I have done, and see if I get to zero.
Now the backlash figure is one you can mess about with until you get it right. My lathe is cheap, and the backlash is quite large (I shall fit ball screws when the pocket and inclination decide) but Mach 3 deals with it very well and I get acceptable results. I must admit I have not done what Rich says and tried to machine a hole into which I press a bearing - I might try that with the milling head.
Perfection - Ah Well !!!