Getting a chatter diagnosis: General Industry Coverage

Dear Doc: I’m getting a bizarre type of chatter marks on a workpiece, sort of spiral-shaped but sort of choppy. There’s a pattern that creates an angle. But if I slightly change the wheel rpm, that angle will change. Any idea what this is?

The Doc Replies: Chatter is the most maddening subject of not only grinding but machining in general. That is because there are hundreds of potential causes. Even Frederick Winslow Taylor (1856-1915), the father of production engineering, said, “Chatter is the most obscure and delicate of all problems facing the machinist.”

It sounds to me like you’re experiencing “fish-scale chatter,” which can occur in stationary dressing (single point, cluster, blade) or traverse diamond disc dressing. (It doesn’t typically occur in plunge-roll dressing.)

Theoretical fish-scale chatter pattern (top) and actual fish-scale chatter
on a round workpiece (bottom). Image courtesy of J. Badger