terrible grinding sound

[BrianG]

Hard to tell the shape of the tooth from the pic, but see the pic below. The one on the right is meant for plastic spurs only and roll very rough on steel spurs. The one on the left is meant for any spur, metal included. It's about the shape of the tooth. Not sure if this what you're talking about, but something to look at. Maybe a pic or a movie so we can hear how is sounds would help.