Changing a standard 3 wheel combination

This guide is applicable to a Sargent and Greanleaf 6700 series lock or similar LaGard lock

This is a procedure you may be asked to do in your general day to day running of a locksmith business. It is a relatively simple operation, that requires only a few specialised tools, and means you can add another skill to your repertoire, that the 2 day locksmith course hopefuls will not be able to do.

S&G Change Key LaGard Change Key
A summary sheet is provided at the end of the article for onsite use as a reminder. You will need the correct change key for the lock in question, and be aware that most locks come in 3 and 4 wheel versions, and require the correct change key for each. Keys are available from the likes of 1010 security (, or if you are replacing one of these locks, a change key comes in the packaging.

Notice on the front of the dial, there is the opening index at the 12 o’clock position, used for dialing in the combination during normal opening of the lock. The change index, is at the 11 o’clock position, and is used for this procedure only.

Opening Index at 12 o’clock position Change Index at 11 o’clock position

In brief the sequence is as follows: 

  • Open safe
  • Throw bolts to lock the safe, but with the door open
  • Dial in the combination to the change index, the first three numbers only, and stop
  • Insert the key into the back of the lock, and turn 90 degrees
  • Dial in the new combination to the change index, first three numbers only
  • Remove the change key
  • Check the new combination fully at least 3 times with the door open

In more detail…

Open the safe, make sure the customer is with you at all times, you don’t want to be accused of anything, or have them remove the contents.

Throw the bolts and lock the safe up again. You may also need into the back of the safe door to access the lock, although some manufacturers cut a hole to allow the change key hole to be accessed.

It may still be worth opening the backpan, this allows you to view the rest of the mechanism, and takes notes, as hopefully you will be called if the safe needs attention in the future.

Dial in the first three numbers of the combination to the change index at the 11 o’clock position, do not turn the dial the last time to open the lock.

Dialling sequence for a 3 wheel lock is as follows; Anticlockwise (left) 4 times to the first number (remember to use the change index), Clockwise (right) 3 times to the second number, Anticlockwise (left) twice to the third number. STOP. This is sometimes written as: 4 x Left to First number, 3 x Right to Second number 2 x Left to Third number. STOP.

The holes in the combination wheels should be lined up with the hole in the case, allowing the change key to be inserted all the way. Notice the cut out in the key that allows it to be turned. Some jiggling and moving of the wheels may be required if the combination hasn’t been dialled exactly. Turn the key 90 degrees, this may be a little stiff, but do not force the key.

Note – Do not try to change the combination with the back of the lock removed, you will damage the mechanism, and not get an accurate combination set. 

Choosing the new combination, some rules:

  1. The last number of the three must not be in the forbidden zone. While this is different for each make and model of lock, generally if you do not se the last number between 00 and 20 this is fine.
  2. This number should not be the birthday of you customer (although it often is), or their son/daughter/other family member.
  3. Numbers in sequence should be avoided, especially rounded numbers, e.g. 10-20-30, 40-50-60, 90-80-70 etc
  4. Dial the new combination to the change index, the first three numbers of the combination only.
  5. A common error is to use the opening index for one or more of the numbers of the new combination, causing the correct combination not to work when testing at the end.
  6. One solution is to cover the opening index while doing this part of the process (a post it note or you thumb will do).
  7. Turn and remove the change key.
  8. Finally, with the door open get the customer to fully test the combination three times. This is to ensure that the combination is the one required, and that the actual sequence of numbers has been inserted correctly, i.e. the change and opening indexes haven’t been mixed up

The sequence for a 4 wheel lock is a little longer, but otherwise identical. It is worth getting hold of a spare lock, as you may find the one you are working on has never had any maintenance, and it might be worth replacing the lock while it still works. A spare lock will also let to practice the procedure before going to site, so it looks a little more professional when you are there. There should be instructions in the box of the new lock, along with a change key. The locks are generally interchangeable, so if you have a LaGard, it will replace an Ilco etc

Other brands of mechanical combination locks have similar change procedures, but they do vary, and of course, the change key will be different, but the Sargent and Greenleaf and LaGard versions are by far the most common.

If you haven’t already, take details of the safe, including lock type, sizes, relocked positions and glass (if any). As you are about to add your business details sticker to the front of the safe, it is you they will call if there is a problem at a later date, and you will want all the information.

Now just time to get your paperwork signed, and time to get paid.

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