Safe Deposit Lock Servicing

Most safe deposit lock servicing boils down to opening and repairing a box when a key is not available.

I’m going to limit my discussion to these four manufacturers who control most of the U.S. market. Mosler has been out of business since 2001, but so many of their locks are in use today that I had to include them in this article. After Mosler declared bankruptcy in 2001, Diebold bought much of the company and still supports many of the former Mosler products. In addition, replacement locks for Mosler safe deposit boxes are now available from third-party suppliers.


Fixed Lever Or Resettable?

Safe deposit locks generally fall into two broad categories: fixed-lever locks and resettable locks. Fixed lever locks have to be disassembled in order to change the combination. This type of lock rarely fails, unless someone damages them, either by trying to force the wrong key to work the lock, or by inserting something other than a key into the lock.

As the name implies, the resettable locks can be reset to accept different keys. Some resettable locks only allow you to reset the renter’s side of the lock and some allow you to reset both sides of the lock. The older a resettable lock is, the more trouble it’s going to give you. Some of the early Diebold and S&G resettable locks used delicate mechanisms that will often slip, causing the lock to fail. The older these locks get, the more easily they can lose their settings.

Modern resettable locks are for the most part ruggedly built and are easy to service. They tend use heavier components that are less likely to slip.


Fixed-Lever Locks

Almost all safe deposit locks use lever tumblers for both the guard and the renter’s keys. Most modern locks use seven levers on the renter’s side, but some older locks may have as few as five. In a new installation, there will generally be the same number of levers on the guard side as well. But in many cases, you will see only a few working levers on the guard side, with spacers between the working levers. This is what is known among safe deposit technicians as “Match Work.” Match Work is done when you have to match a new lock to an existing guard key, which may have originally been made for a completely different kind of lock. You will see this in older banks where additional “nests” of safe deposit locks have been added after the original construction.

A good example of a simple fixed-lever lock is the Sargent & Greenleaf 4400 series of locks. These simple locks may be the most common safe deposit locks out there. Like most safe deposit locks, they are available in both a right-hand and a left-hand version. Most of the safe deposit locks that you will work on will be right-hand locks. Generally, the left-hand locks are only used on the last row of boxes in a nest so that the door will swing away from the wall if the nest is mounted in the corner of the vault. The lock shown in these photos is a right-hand lock.

Note: Review the terminology in the sidebar on page 37 to help understand the operation of the lock.

When the guard key is inserted and turned, it aligns all of the gates in the guard lever stack with the fence on the guard side of the lock bolt. Then, when the renter’s key is inserted, it aligns all of the gates in the lever stack on the renter’s side of the lock with the fence on the renter’s side of the lock bolt. As the key is turned further, the foot on the renter’s post contacts the lock bolt and pulls it back to unlock the box. If any gate on either side of the lock is not properly aligned, the bolt cannot be withdrawn because one or both of the fences will be stopped by the lever that is not properly aligned.


Opening Boxes Equipped with Fixed-Lever Locks

In almost every case, you will have a working guard key for any safe deposit lock you will need to open. Invariably it is the renter’s key that either gets lost or is unavailable.

You could drill a hole in the safe deposit box door above the gates and then manually pick each lever, but that is something that you want to avoid if at all possible. In fact, most banks won’t let you drill a door under any circumstances. The only time I have ever used that procedure was on a bank with antique locks that simply could not be replaced. Even then, I had to be extremely careful to drill the smallest hole possible and to make my repairs to the door as invisible as possible.

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