While I still consider myself a CNC noob, because I know I still have much to learn, meaning I don’t know how much I have yet to learn , I figured this little design is a very good test for concentric circles.
You may recognized the design from a recent TV show trinket/prop. Its designed to be milled with a 1/4 bit, but you could do it with a smaller bit, it would just take longer.
As seen, it was carved in pine and its roughly 8 inch in diameter.
I used very conservative feed and speed: 13,500 rpm, DOC 4mm, Feed 200 mm/min, 2 flutes 1/4 carbide bit.
See attached stl, and find the original exported Fusion 360 source. I placed a 6mm bearing ball in it, and my 5 year old loves to play with it.
Friends of the TV show surely will enjoy and yourself curse at it if your machine is not completely fined tuned.