I broke one just like that the other day, first time ever! My set screw had never been loose so there was no wear on the pin or weight, so even with the pressure of the set screw on that spot there was really no clearance for a pressure bend on the pin. I wrote it off as fatigue at the pressure point and put another bolt in. I felt real lucky than my clutch did not come apart too. Sure made a bang when the first half flew out and another bang when I let up and hit it again and the other half flew.