A bar material supplying device includes a feed rod having a leading end provided with a finger chuck, a feed rod servomotor and an air cylinder device that move the feed rod in a longitudinal direction to insert and pull the bar material into and from the finger chuck, and an NC device that controls driving of the feed rod servomotor and driving of the air cylinder device. The NC device controls the driving of the feed rod servomotor and the driving of the air cylinder device to move the feed rod in an operation of inserting and pulling the bar material into and from the finger chuck, and operates as an error allowable device that allows an error of an operation amount of the feed rod servomotor motor in the operation of inserting and pulling the bar material into and from the finger chuck.

A machine tool improving measurement accuracy of a machined workpiece diameter. A machine tool comprises a displacement sensor mounted on at least one of a guide bush and a spindle supporting unit. The machine tool further comprises a calculating unit which calculates a diameter of the machined workpiece based on a measurement value of the machined workpiece by the displacement sensor. The spindle is movable back and forth in an axial direction. The spindle is retracted after machining to bring a machined portion of the workpiece to a predetermined measurement position in the axial direction to allow the displacement sensor to measure the machined portion.

A machine tool improving measurement accuracy of a machined workpiece diameter. A machine tool comprises a displacement sensor mounted on at least one of a guide bush and a spindle supporting unit. The machine tool further comprises a calculating unit which calculates a diameter of the machined workpiece based on a measurement value of the machined workpiece by the displacement sensor. The spindle is movable back and forth in an axial direction. The spindle is retracted after machining to bring a machined portion of the workpiece to a predetermined measurement position in the axial direction to allow the displacement sensor to measure the machined portion.

An apparatus includes a self-centring device for centring and guiding a bar, tube or the like to be advanced to a spindle of a machine tool, includes a hollow containing body with through opening having a longitudinal axis, for receiving a bar to be fed along an advancement direction to the spindle; in the body an inner sliding surface is defined that is tilted with respect to the longitudinal axis; centring and guiding elements are provided housed in the hollow body and shaped for coming into contact with the bar and exert thereupon a distributed centring and guiding action; the centring and guiding elements that are slidable along the inner surface for the distance thereof from the longitudinal axis to adapt to different bar diameters; in the body an elastic member is housed to urge the centring and guiding elements to the position of minimal reciprocal distance so as to induce and maintain, during operation, the centring and guiding elements in contact with the surface of the bar. An advancement device is further disclosed for the bar, having a supporting and guiding member configured for restingly receiving, from a first side, a bar and configured for guiding said bar along an advancement direction, a movable grasping member mobile from a disengaged position, further from the member to be separated from the bar, to a locking position, nearer said supporting member to press longitudinally the bar from a second opposite side against the supporting member; advancement motor device is configured for rotating the supporting and guiding member and/or the movable grasping member in the locking position to draggingly advance the bar along the advancement direction.

An improved spindle assembly for a Davenport multi-axis screw machine is adapted to adequately hold one-inch round bar-stock in a collet against movement relative thereto attributable to machining operations performed on a cantilevered length of bar-stock held in and extending beyond the collet. The spindle assembly may permit the use of the screw machine on materials thought heretofore to be too difficult to machine on a screw machine. Cam surfaces on the inner spindle and collet may be coated with a low-friction material. A stress-relieving connection between the inner spindle and collet is provided.

An apparatus for feeding bars to a machine tool including an end adjacent a working zone in which a spindle is provided; a drum element, rotatable around an axis; a movable support provided on the drum element for supporting and guiding a bar parallel to the axis. The movable support slidably drivable on the drum element parallel to the axis between a disengagement retracted configuration and an engagement extended configuration. The movable support having telescopic tube configured for being received inside tubular housing and guide for coupling with the spindle. The telescopic tube defines, a cylindrical containing structure configured for enclosing and supporting in a distributed manner a respective bar along the entire supporting zone, so as to prevent the bar from flexing because of the centrifugal actions generated by rotation.

A lathe capable of facilitating maintenance of a chucking mechanism. A chuck operating apparatus includes a claw and a shifter to open and close a chuck provided on a spindle. The tilt claw provided outside the spindle has a first posture to bring the chuck into the opened state and a second posture to bring the chuck into the closed state. The shifter provided outside the spindle and movable in a spindle axis direction is brought in a first position to bring the claw into the first posture and in a second position to bring the claw into the second posture. A roller is mounted on the shifter in a contact position with the claw to roll in the spindle axis direction.