This application came across my desk last week and for the life of me I couldn’t think of where someone would use it.  I don’t remember ever being asked for a rim cylinder with a thumbturn, and people ask me for all kinds of random things.

For anyone who has wondered about the difference between a rim cylinder and a mortise cylinder and which one to use where, it basically depends on what kind of locking hardware the cylinder will be used with.  Mortise cylinders are threaded, and have a cam on the back.  Rim cylinders attach with screws and have a tailpiece on the back.  The lock/panic hardware manufacturer’s catalog will show which type of cylinder is needed.

Last week one of the Ingersoll Rand specwriters was looking for a rim cylinder with a thumbturn.  Thumbturn cylinders are typically mortise cylinders and are used with mortise deadbolts, narrow stile locks, etc.  Schlage offers a thumbturn rim cylinder as a special product (product #XB11-979).  It was designed for use on a Von Duprin 98/99 exit device with the -2 option (ex. 99L-2).

The -2 option is a cylinder on the active head of the panic device, which can be used to lock or unlock the outside lever handle (or other trim).  The Von Duprin rim device uses a rim cylinder for this function, and the mortise device uses a mortise cylinder.  The thumbturn rim cylinder allows the locking/unlocking to be accomplished without a key, for areas where the convenience of a thumbturn is preferred over the security of a key cylinder.  The thumbturn position also gives visual confirmation that the lever handle is locked.

Any other ideas about where a thumbturn rim cylinder would come in handy?

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