Parlec B40-77TT4 Tapping Heads; Shank Type: Taper Shank; Shank Diameter (Inch): 1; Taper Size: BT40; Minimum Tap Capacity (mm): M3; Minimum Tap Capacity (Inch): #6; Maximum Aluminum Tap Capacity (mm): M39; Maximum Aluminum Tap Capacity (Inch): 1-5/8;