I was trying out some bits that I had just ground & fooling around with the independent feed on my lathe when I got this strange ripple pattern. The ripple peaks are about .030 apart, but the feed was only .002. And the ripples are rings, not a helix. It's mystery metal.
I'm speculating that there is a rub-then-cut kind of oscillation going on. That is, the .002 feed is not enough to get a bite on the steel, so it rubs a while, without cutting until enough advance occurs then it bites/cuts until the pressure is relieved and goes back to rubbing again. Does that sound right (it's not real clear how that would give a ripple pattern)?
If so, is there a way to avoid it? I thought that I had the bit pretty sharp (it was just a plain RH roughing bit). Could it be lack of rigidity in the lathe?