Cutting tool lock nut having grooved collet-locking surface and cutting tool incorporating same

A cutting tool (101), comprising:

• a cylindrical chuck (112) having a conical bore (110) and an external chuck threaded portion (114) extending along the periphery of the chuck (112);
• a compressible collet (102) having a conical collet body (104), a collet head (105) and a cylindrical collet bore (106) with a bore diameter (D) for receiving a tool shank (108), the collet bore (106) opening out to the collet head (105) and defining a longitudinal collet central axis (A);
• and
• a lock nut (100) defining a lock nut central axis (B) and comprising:
• a nut portion (116) having a lock nut front end (118) provided with a lock nut front opening (119), and an cylindrical inner surface (120) extending about the lock nut central axis (B) and provided with a lock nut threaded portion (122);
• and
• an inner locking portion (125) located within the nut portion (116) adjacent the lock nut front end (118), the inner locking portion (125) having a collet-locking surface (128),
• wherein:
• the collet (102) is fitted into the conical bore (110) of the chuck (112),
• the nut portion (116) is located over the collet head (105), and the lock nut threaded portion (122) engages the chuck threaded portion (114), until the locking portion (125) presses on the collet head peripheral surface (109), thereby compressing the collet (102) towards the collet central axis (A), to grip the tool shank (108) in the collet bore (106), and the lock nut (100) being suitable for locking collets (102) with different bore diameters (D), and
• the locking portion (125) has at least one angled coolant groove (130) recessed in collet-locking surface (128) and opening out to both the collet-locking surface (128) and the lock nut front opening (119), and when the chuck (112) is provided with a coolant fluid (C), the coolant fluid (C) flows through the chuck (112) and through the collet (102) towards the locking portion (125), passing through the at least one coolant groove (130) between the locking portion (125) and the collet head (105).

A cutting tool lock nut (100) having a lock nut central axis (B) and comprising:

• a nut portion (116) having a lock nut front end (118) provided with a lock nut front opening (119), and a cylindrical inner surface (120) provided with a lock nut threaded portion (122), the lock nut front opening (119) having a lock nut front opening diameter (D1);
• and
• a locking portion (125) located in the nut portion (116) adjacent the lock nut front end (118), the locking portion (125) having a collet-locking surface (128) tapered at a first non-zero taper angle (α) relative to lock nut central axis (B);
• wherein:
• the locking portion (125) has at least one recessed coolant groove (130) recessed in the tapered collet-locking surface (128) and opening out to both the collet-locking surface (128) and the lock nut front opening (119);
• and
• the at least one coolant groove (13) is configured to convey a cooling fluid (C) in a direction of the lock nut axis (B).