Glass edge chipping: six causes and how to tell them apart

Chipping has six common causes and they look nearly identical on the finished edge. Work through them in order, because the cheapest fix is last on most people's list. One: the wheel is glazed rather than worn — the bond has smeared over the diamond and stopped cutting, so it rubs and chips instead. Dress it and the problem may disappear. Two: grit sequence has a gap of more than two steps. Three: feed rate is too high for the glass thickness.

Four: coolant is weak, dirty or aimed at the wrong spot. This is the most commonly missed cause — insufficient coolant means the wheel heats, the bond softens and the diamond pulls out. Five: the wheel is out of true or the spindle has play. Six: the wheel really is worn out.

The fast diagnostic: look at the wheel's cutting face. Glazed looks shiny and loaded with grey paste. Worn out looks smooth with the diamond layer visibly thin at the edge. Out-of-true shows as one bright band on an otherwise even face. Each of those points at a different fix.