Further to my previous reply, I forgot a very important parameter to set in SU.
Model scale.
For the size most printers can make, you need curves with very short segments, but SU doesn't work well with very short lines, especially at the high resolution most printers are capable of.
So you need to use a large scale for the drawing. Then in your slicer scale it down to life size.
The simplest way is to go metric for the drawing, and draw in centimetres, where 1 cm is 1 mm printed. A 10:1 scale that is easy to visualize and compute. It is just a simple mental moving of the decimal point in your measurements.
I know it is tough for North Americans to work in metric. Even for me, in Canada, which is supposedly metric, but not us old folks. I only use metric for 3D print designs. F.P.S everything else.
Then all you need to do is set the slicer at a 10:1 ratio and print. No complex ratio conversion math.
One other thing. For curves in your model, such as bearing mounts, gear teeth, use a high number of segments. That will allow a smoother fit. Same with bolt holes that are not threaded by the bolt. For screws and bolt holes that are force threaded by the screw/bolt, go with larger segments, I use 12 for a full circle. That will give a bit more thread bite in the final part, so fewer segments in the hole are not critical.
Where curve surface smoothness is not important, use large segments. That will also speed up the printing a fair bit.
Finally, you really need to experiment with practice parts at various segment sizes, nozzle sizes and slicer parameters before printing for real.