Bit jogging ever so slightly

[morbious1]

I am machining a pocket using 4 passes to a depth of .6 inches. As the bit travels around there are 4 places where the bit jogs in enough to create 4 divots. A set of 2 divots shows in the photo and there are 2 more just like these on the opposite side of the circle. Due to the divots, the circles are out of round just enough to give me assembly issues. Any ideas?

[Jimcad]

Bear in mind that I'm new and know almost nothing.
But . . . . my first thought is backlash????????
Are you on Leadscrews or Ballscrews ??

Jim

[Jimcad]

Just looked online.
Ballscrews.
Wait for someone who knows what they're talking about.

[Rcnewcomb]

Do the divots appear in the preview?
Do the divots line up with the nodes in the circle?
Does the spindle or machine change speed at those points?
Are the divots always in the exact same spots?

[morbious1]

No, divots do not appear in the preview.

Nodes are at 12, 3, 6 and 9

Each set of 2 divots are about 1.5 inches apart and are not aligned with the nodes.

No speed change.

Divots are in the same 4 locations. I am cutting at .125 depth for each pass and each of the 4 divots line up at each pass to give the appearance of it being the full depth of the cut. The first 2 divots are on the north end of the piece being machined and the 2nd set of divots are on the south end of the piece but they appear to line up left to right.

[Rcnewcomb]

Sounds like a mechanical issue. A call to Shop Sabre tech support should get you sorted out.

[morbious1]

Thanks R, waiting in queue as we speak.