Is this a bug or operator error?

Following @WillAdams advice to avoid slotting cuts to improve accuracy and finish, I set up a 12mm pocket to be cut with a 6.3mm bit using a 3mm stepover. I expected a slot down the center with a ~3mm step to each side to finish the pocket; however, what I got was a slot down one edge of the pocket with a ~6mm step (nearly full cutter width) to finish the other edge of the pocket. Other pockets in the same job that were wider than 12mm started with a slot, a ~6mm step, followed by enough 3mm steps to finish the pocket. Why is the first step at or near the bit width? Is this a bug or do I not understand what a pocket toolpath should do? I’m using build 431 of Carbide Create running on a 6 year old Macbook.

The pockets are being cut to the correct size just not the way I expected.

Attached is the .c2d file; see toolpath ‘top A’ for a 12mm pocket, or ‘bottom A’ for a wider (151.7 KB)

Thanks in advance for your help!

yup this is a long standing know bug that is apparently hard to fix…

Off the top of my head, and without firm basis for the following statements (I don’t use CC), you might try:

Lying to CC about the size of the bit, (maybe 0.5mm larger than actual) for a rough pass, then tell it the truth and run a second pass. The first/rough will be narrow, second will have uniform small radial engagement for accurate finish)

Use a smaller tool (less than 1/2 slot width) to see of that gives the correct behaviour.