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The D-Series lock was manufactured by Schlage Lock Company, beginning in 1940. The first major change to the D-Series lock occurred in 1989, when Schlage introduced the lever handle D-Series locks. In 2003, Schlage re-engineered the D-Series lock to improve life expectancy, operation and ease of installation. Re-engineering the D-Series locks has resulted in a 12 percent increase in the average lock weight due to the increased use of steel components.
The steel spring cages of the new D-Series locks are now integrated into the spindles. The spindles are attached directly to the spring cages, which in turn are permanently mounted to a 0.060" thick zinc-plated steel plate that has been deep drawn to create the shape. This eliminates the old style driver and the plastic insert. Rotating the new D-Series lever approximately 60 degrees retracts the retractor, permitting the door to be opened. The new latch bolt is powdered metal and the length has been increased to provide additional resistance to attacks.
The old mechanism, a steel hub with roller retractor secured together using two cotter pins, has been replaced. The new die-cast powdered metal and steel mechanism is screwed together with inside hub secured to the outside housing. The spring-loaded, powdered metal retractor slides against zinc plated steel insert. This new configuration is able to achieve tighter tolerances of + 0.005", reducing lever wobble and droop.
Another result of the re-engineering is improved operation and an average of 36 percent fewer parts. As an example, the old style Schlage D53PD has 17 parts when counting an assembled chassis as one. The new style Schlage D53PD has 12 parts. The D-Series locks are easier to install as a result in the decrease in parts.
Additional changes to the new D-Series locks for tamper resistance include:
- The new locking lug is twice as thick as the old locking lug.
- The spindle sleeve portion of the new levers is approximately .020" thicker, and the plastic insert cavity is closed and extended to accommodate the bible of the lock.
- The new D-Series locks are using heavier gauge thru-bolt screws with fine threads.
- Adjustment plate markings are on the chassis at 1-3/4" and 2". The D-Series lock chassis adjusts for 1-5/8" – 2-1/8" thick doors without additional parts.
- The steel spring cage housings eliminate the need for an add-on metal plate for fire resistance.
- For locks equipped with pushbutton interior locking, the chassis spindle has a plastic sleeve for smooth operation. The outside chassis spindle is made of powdered metal to provided increase operational life and to resist attacks.
The new D-Series locks are visually very similar to the old style. The outer diameter of the roses is the same size. To compensate for the elimination of the drivers, the new style rose has been extended and is conical shaped along the spindle. The return on the new levers is approximately one-half inch longer.
For a new installation of the new D-Series lock, the three cross bore openings and one edge bore opening are the same as required by the old style lock. To install the new D-Series lock:
Teachers can lock or unlock their classroom doors from the inside for added safety in an emergency.