.010" egg-shaped while circle milling.

[RussMachine]

Yikes!!

I was circle-milling some bores yesterday, and they were coming out .010" egg-shaped.
Y axis seems ok, as the bore was on size, but in X, I was getting +.010"

Would this be a backlash issue? Or is it loose Gibs?

Looks like it's time to tear the mill apart and tighten everything up.

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[jwatte]

It could be loose gibs on Y, or backlash on X, or even perhaps some slop in the head/spindle. Sure hope it isn't the last one!

[machinehop5]

...is frontlash possible? Newton's Law of motice
https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion

[Tbkahuna]

What material and size and how were you holding it? I've seen egging like that in plastic parts held in a vise. The vise was compounding a little bit of out-of-round. If there is any flex in the piece that could be contributing to seeing something egged more than expected, even in metals.

Do you see the same amount on different size holes?