CCH Exclusive Signature Series, Bit Key Mortise Lock


Case: 4" High x 3 ⅜" Deep x 11/16"
Face: 5 ½" x 1"
Backset: 2 ½"
Faceplate/Armored Front Thickness: 3/16"
Knob to Thumb-Turn/Bit Key Spacing: 2 ¼"
Knob Hub: 7.3 mm broached on diamond. 7 mm broached on square.
Thumb-Turn Hub: 3/16" (5 mm) on the diamond.

1 each: Lock
1 each: Faceplate
1 each: Traditional Lip Strike
1 each: Solid Brass or Stainless Steel Dust Box
1 each: Solid Brass Bit Key

Sold Each

Bit Key locks are keyed alike. Limited custom key-work available upon request.

Made exclusively for Crown City Hardware in the USA.
Item Number: 31C

Crown City Hardware is proud to offer our exclusive, Signature Series, interior bit key mortise lock. Crafted to our specifications, this lock is designed and engineered to be the finest interior mortise lock you can buy, and at a remarkable price.

Our 31A and 31B mortise locks have for years been the industry standard for traditional interior mortise locks. Nonetheless, we knew we could improve upon them. Relying on nearly 100 years of experience, we set out to create the best interior mortise lock on the market. Our new 31C bit key mortise lock & 31D privacy lock are simply that, the best interior mortise locks you can buy. They are the only locks we've ever been willing to designate with our coveted "Signature Series" rating and allow to carry our Crown City Hardware logo.

In order to create this lock we worked with the finest lock manufacturer in the U.S.A. Building on what was already a superb foundation, our new lock was custom crafted to our specs and designed to function flawlessly in the restoration market. The result is a lock that feels so precise, so finely crafted, that simply turning the door knob reminds you of the feel of a luxury automobile. No slop or play in the latch, and a satisfying snap when the bolt is thrown or retracted.

  • The case is forged from heavy gauge steel and designed to last for decades. It is sized to fit most original mortise cutouts with minimal to no carpentry required.
  • Rare for interior mortise locks, usually reserved for high end entry grade mortise locks like our 950A, it features a heavy duty armored front that's adjustable to your door bevel. 
  • A wrought brass face plate, available in several finishes, attaches to the armored front using solid brass, period appropriate slotted head screws. You can change the finish of your lock by simply replacing/refinishing the face plate without the need to remove the entire lock from your door!
  • A solid brass or stainless steel latch with a full 7/16" throw. For durability and precise function, the latch mechanism features not one or two, but three springs.
  • A solid brass or stainless steel privacy bolt with a full 1/2" throw. 
  • Interior mortise locks rarely include a dust box. Even the high end entry locks or latches that do include them use plastic boxes. Our lock includes a solid brass or stainless steel dust box that’s been finished to match your lock & strike!
  • A custom designed hub that universally accommodates both diamond & square broached hardware. It works with all of the door knobs we sell without adaptors!
  • A solid brass strike plate designed to match originals with the lip only extending for the latch, rather than the more common full lip strikes found on today's locks.
  • The bit key version features a solid brass bit key that looks fantastic. You'll want to leave it in your lock to accent your door!
$109.99 to $114.99 $99.99 to $109.99
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