Allied Machine and Engineering HYD-BT30I0750 Hydraulic Tool Holders & Chucks; Shank Type: Taper ; Taper Size: BT30 ; Hole Diameter (Inch): 3/4 ; Hole Diameter (Decimal Inch): 0.7500 ; Shank Diameter (Decimal Inch): 1.2500 ; Shank Diameter (mm): 31.75