Abstract: A cylindrical lock on a door panel has an outside actuating lever and an outside nut. Torque from both the nut and the outside lever is transferred to a substantially planar torque plate engaging the door panel and having a central opening bounded by arcuate edge surfaces spaced away from external threads on the lock hub. The central opening is also bounded by chordal edge surfaces disposed next to chordal surfaces on the lock hub. The nut has chordal surfaces next to the chordal surfaces of the torque plate and has arcuate surfaces close to the arcuate surfaces of the torque plate, all of such surfaces being in the plane of the torque plate.

Abstract: A mortise lock having reversible features to permit accommodating both left and right hand door applications. The lock includes the novel features of a resilient fire stop, simultaneous retraction of both the dead bolt and latch bolt mechanism by operation of the interior handle, and a three-position thumb turn function which variously unlocks the lock, locks against operation of the latch bolt by the exterior handle and finally, locks the latch bolt against operation by the outside handle and deploys a secure dead bolt. Other features of the lock include clockwise and counter clockwise rotation of either handle, separate rotation of the inside and outside handle and an auxiliary latch which prevents externally induced retraction of the latch bolt when the door is closed. Features also include an auxiliary lever handle assist spring. A new slide plate and cam operated lock works are provided to accomplish the locking function of the present invention.