Abstract: A speed-up spindle unit including a non-rotative housing having a fixed ring, a sun roller secured to a high speed spindle rotatably carried in the housing and a plurality of planetary rollers rotatably carried in such a manner as to be in contact with the fixed ring at one peripheral end and the sun roller at the opposite peripheral end so that the planetary rollers individually rotate about their own axes while they revolve about the sun roller, thereby transmitting a torque from the planetary rollers to the high speed spindle through the sun roller.

Abstract: A chuck assembly for use in a machine tool for holding a tool element comprises a chuck body having a sleeve integrally formed therewith so as to extend in the direction, which sleeve has a support bore defined therein for the receipt and support of the tool element and also has its outer peripheral surface tapered in a direction away from the chuck body, a fastening nut having its inner peripheral surface tapered in complemental relation to the outer peripheral surface of the sleeve and helically rotatably mounted on the sleeve through a plurality of roll bearings, and a reinforcing nut threadingly mounted on the fastening nut and adapted to be engaged under pressure with the chuck body when the fastening nut has been fastened and the reinforcing nut is then fastened.

Abstract: A keyboard having multiple key-switches each comprising a key having a finger-pressed top face, a movable electrode and at least two stationary electrodes. The keyboard comprises a key holder plate of generally planar flat shape supporting the multiple keys in plural rows movably in a direction perpendicular to a plane of the key holder plate, and retaining device for holding the key holder plate downwardly convexed in cross section across the plural rows of keys, with elastic deformation of the key holder plate. The key holder plate has a deformation-facilitating portion located between each pair of rows of keys, and having a longitudinal recess array formed in parallel to the rows of keys, having a plural number of recesses in the upper and lower surfaces of the key holder plate, as viewed in a direction perpendicular to the rows of keys.

Abstract: A tap holder adapted for attachment to the main spindle of machine tool to cut internal threads in a workpiece, the tap holder including a floating mechanism by which the tap holding spindle is smoothly moved in the axial direction, the floating mechanism being featured by a single coil spring compressible in association with the axial movement of the tap holding spindle, and by its feasibility that a possible error occurring between the lead of the tap and the feed of the main spindle of the machine tool is automatically corrected.