Circle carve outs are more like ovals?

Has anyone run into an issue with circles carve outs being more like ovals? It seems to cut a nice circle when you set it to cut along/inside/outside the path, but the carve out is not looking like a perfect circle. Any suggestions on what could be the issue. The circle carve out size I’m trying to produce is about 0.4" in diameter. Not sure if the size is an issue. Here is link to my project…hopefully this link works.

Have you calibrated your machine, or are your X and Y steps/mm ($100 and $101 GRBL settings) at their default values?

Provided the X and Y axis is correctly calibrated, $100 and $101 values are good:

Oval circles is due to different rigidity/backlash component from X to Y axis. As the cutter move through the material its being pushed sideways from the cutter forces => it will deviate slightly off path.
If the X/Y rigidity is different the deviation will be different between the two and in effect cause an oval.

Since the deviation is a “fixed” amount it will appear much stronger on smaller circles vs big ones.

Solution: Tighten up your machine to the best of your capacity, ask specific questions here in that regard. Also, the harder you carve (wider bit/faster feed rate or deeper per pass) the greater the offset will become. So you may also try to carve more gently.


No, I don’t believe I’ve calibrated the machine but don’t remember a step for that in the instructions?? Must of missed it. Let me try that first and also make sure the X,Y axis are tight.

THere really isn’t anything in the build instructions that will help with the calibration of the X-Carve.
There are however several good discussions on this Forum about calibrating the machine.
There are also some good external links to Step/mm calibration sheets.
do a general search for “calibration” take an hour or three to read through some of the threads.
You will be glad that you did…