An apparatus for releasably holding a tubular toolholder shank by axially reciprocating a lock rod between a locked and unlocked position. Compression balls following a helical path on a torque nut are used to retract a compression sleeve, which in turn compresses springs against the lock rod to move the lock rod into the locked position. As a result, a repeatable lock rod force is possible with a pre-determined and self limiting rotation of the torque nut. The same helical groove may be used to advance the compression sleeve against the lock rod to urge the toolholder from the base member.