|Lock Design||Pin-tumbler, Dimple|
|# of Components||20|
The 917 is a pin-tumbler lock made by the Japanese company WEST. The 917 has a dimple key, and multiple bibles containing 20 pins, arranged in rows of seven on the left and the top of the vertical keyway as well as six on the right. The 917 employs the same pins, fundamental designs, and primary security features as the smaller, 12-pin WEST 916 model.
Principles of operation
The WEST 917 a pin-tumbler lock operated by a dimple key. The lock uses 3 bibles with 21 chambers for pin-tumbler stacks. There are seven pin chambers in the top and left side rows in the plug, as well as six chambers in the row on the right side. Each of those chambers contains a set of key pin, driver, and spring. A seventh chamber in the bible on the right side contains a spring-biased bearing that aligns with an indent to center-bias the plug.
The dimple key of the 917 has four cut depths for side pins and three, different cut depths for pins in the top row. The key is bitted on the sides and edges of the blade and is reversible. To open the lock, all 20 key pins -- across all three rows of pins -- must be aligned at the shear line. (See also Pin-tumbler, Principles of operation)
WEST utilizes a variety of security pins to deter lockpicking and destructive attacks. Pin stacks incorporate stainless steel key pins with two sizes of brass driver pins to match. The 917 uses a mix of mushroom spool drivers and standard ones. Drivers are cupped to allow the spring to nest inside the pins. Key pins are a combination of t-pins and multi-section tapered spools which are torpedo shaped to create overset traps. These pin designs match over- and/or counter-milling of the pin chambers in the core to catch pins as they are lifted to shear.
|West 917 pin sizes (mm)|
|Top row pins||4.0||4.4||4.8|
|Side row pins||4.6||5.0||5.4||5.8|
The WEST 917 is disassembled in the same way as a traditional pin-tumbler cylinder.
- Remove the rear plate
- Insert the key and turn the plug 30-45 degrees.
- Withdraw the plug from the cylinder. (A plug follower and core shims are strongly recommended)
- Note: the three bible covers of the cylinder can be removed easily and non-destructively.
- This makes gutting and re-pinning possible without removing the plug.
West 916 & 917 key comparison
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