Counterbores H with a diameter of 50mm and larger are all made with a driving lip. These sizes should be used in the appropriate type M toolholder. Dimensions (mm) H & HA Counterbores H and HA with Ø of 50 mm and larger are all made with a driving lip. These sizes should be used in the appropriate type M toolholder. d: 14.0; d1: 6.0; d2: 8.0; L: 48.0; L1: 28.0.