Tap holder

Claim 1

A tap holder adapted to be attached to a spindle of a machine, comprising a cylindrical body to be rotated by said spindle, said cylindrical body having first and second means for defining a first space at the inner periphery thereof, said first and second means being axially spaced from each other to define the axial ends of the first space, a tap holding spindle slidably situated in said cylindrical body, said tap holding spindle having means to receive a tap at a forward end thereof, and third and fourth means for defining a second space at the outer periphery thereof, said third and fourth means being axially spaced from each other to define the axial ends of the second space, the axial length of the second space being equal to the axial length of the first space, means for transmitting torque from said cylindrical body to said tap holding spindle, said torque transmitting means being coupled to the tap holding spindle so that the tap holding spindle can be axially moved relative to the cylindrical body, a floating mechanism situated in the first and second spaces of the cylindrical body and the tap holding spindle, said floating mechanism having a first stop ring to abut against the first means of the cylindrical body and the third means of the tap holding spindle, a second stop ring to abut against the second means of the cylindrical body and the fourth means of the tap holding spindle, the diameter of the second stop ring being radially changeable upon exertion of radial force thereon, and a spring situated between the first and second stop rings, and means for imparting restricted movement to the second stop ring, said means for imparting restricted movement being formed on one of the inner surface of the cylindrical body and the outer surface of the tap holding spindle so that when the tap holding spindle is urged in the axial direction relative to the cylindrical body, the second stop ring initially engages with and finally passes through the means for imparting restricted movement by changing the diameter of the second stop ring, said second stop ring being smoothly moved after passing the means for imparting restricted movement, whereby when the tap holder is actuated initially, the tap holding spindle can be relatively strongly pushed against a workpiece to allow the tap to bite the workpiece but the tap holding spindle can thereafter be held almost floatingly relative to the cylindrical body.