Spindle lock-up device

A lock-up device for detachably connecting a rotatable spindle having a tool holder at its free end to the ram of a vertical boring machine to provide a fixed tool holder for said ram, said spindle being rotatably journaled in said ram by sets of bearings, said lock-up device comprising a housing fixedly secured to the distal end of said ram and surrounding the free end of said spindle, a first annular spiroid gear member surrounding said spindle and fixedly secured to said ram, a second annular spiroid gear member surrounded by said first gear member and fixedly secured to said spindle, a third spiroid gear member surrounding said spindle adjacent said first and second gear members, guide means slidably connecting said third gear member for axial movement relative to said first and second gear members, said first and second gear members each having teeth facing said third gear member said third gear member having teeth facing said first and second gear members positioned to simultaneously interlock with the teeth of said first and second gear members when said third gear member is moved axially relative to said spindle from a retracted to an extended position, spring means normally biasing said third gear member to its retracted position, an annular chamber in said housing facing said third gear member, an annular piston in said chamber movable from a retracted position to an extended position in which said piston moves said third gear member to its extended position, and conduit means for introducing fluid under pressure into said chamber to move said piston to its extended position, whereby to displace said third gear member into engagement with said first and second gear members to lock said spindle against rotation relative to said ram, said third gear member and said piston returning to their retracted positions under the influence of said sping means upon the venting of fluid from said chamber, thereby freeing said spindle for rotation relative to said ram.