On the RotoZip tool... I successfully burned out not 1 but 2 of the battery operated models, and over 10 bits cutting in about 10 boxes for cable/tele on wall(s) made with cementboard and sheetrock (about 1"). When I bought the electric model...10 hihats, 2 switch locations, 1 bit! (same job location) I haven't seen the battery model for sale in some time now - maybe it had a manufac. defect?
