External turning Introduction  Great for high pressure coolant JCT series D Excellent chip control and long tool life with high pressure coolant Large holder lineup for turning, external grooving, cut-off and threading Unique coolant system for various machining applications : Coolant hole Advantages of internal coolant Discharges coolant towards the cutting edge Internal coolant provides longer tool life and excellent chip control Extended tool life Improved chip control Wear resistance comparison (Internal evaluation) Chip control comparison (Internal evaluation) Internal coolant (7 MPa) External coolant (0.4 MPa) Internal coolant (7 MPa) External Coolant (0.4 MPa) Cutting conditions: Vc = 200 m/min, f = 0.05 mm/rev, ap = 0.5 mm, wet, DNMG150408 type, workpiece: 15CrMo4, external turning Cutting conditions: Vc = 250 m/min, f = 0.3 mm/rev, ap = 2 mm, wet, CNMG120408 type, workpiece: 34CrMo4, external turning after machining 42.2 min D4