How come a 68mm dia circle is 67.5 when done

Circle - 68 dia fill, DOC = full material height. Bit size is correcly set.

When done, I check with my digital caliper and inside the circle is ~67.5mm across, not the 68mm I expected.

Any tips?

Could be a calibration issue. Also have you physically confirmed the size of the bit you are using, that could be a part of it. Other than that, maybe do the usual checks of belt tension, v-wheels and make sure your stepper pots are adjusted properly.

Could be cut path. Make sure you’re carving either Inside or Outside the circle to get exact circle size you’re looking for.
If you’re making pocket inside to circle, you have to cut inside, vise versa. Wish to see the picture you can post, then we can come up with better idea.

I would definitely measure your bit…I’ve had a few that were smaller then advertised by a little.


I’ve added a composite picture of the various settings in the Easel project.
I will measure my 2 flute straight bit that I used for this. It might be smaller than stated.

Also I will remeasure the circle cutout when I get home from work. Perhaps I do have a calibration issue with the machine.
I did swap the standard 300w spindle for a Makita the other day, but test shapes after the upgrade looked good enough so I haven’t recalibrated and squared the thing.

Anyway, I’ll post more info later. We shall find a fix for this :smile:

Thanks for all input so far. Appreciate it

best thing to do first is cut a 2x5 box and measure horizontal, vertical and diagonal. this will tell a lot of things, post the results and we’ll see if we can help. Very hard to judge with a circle

3x4 inches?

Doh… Didn’t think that far/have long since forgotten what I learned in school.
Thanks. :smile:

Regarding cutting out a square…
Before failing on the circle I cut out a test for a friend and colleague of mine. The intended dimensions were 90x60mm and the results are dead on. We have measured it using two different rulers and agree - the cut is dead on. Never mind the failed circle top right, the piece came loose. :smile:

Also the two circular indentations are 20x20mm, exactly as intended.

I will run another test with a square in the evening to check if the diagonal is as expected. But so far it appears my machine is calibrated correctly. What do you think?

Ok… Results. Bit is ~6mm on the widest.

Cut out a x40mm x y30mm square, outside cut. 3 measurements pr side(top, middle bottom):

A—40mm —B
| |
30mm |
| |

Side AC -> BD

Side AB -> CD

A -> D

B -> C