How to Rekey a Mortise Lock

A mortise lock is the heavy, full-bodied lock case set into a pocket cut in the edge of the door: Schlage L9000, Sargent 8200, Yale 8800, Corbin Russwin ML2000 and their cousins. You find them on commercial doors and on pre-1970s Vancouver houses and apartment blocks.

Mechanically the cylinder is an ordinary pin tumbler and it rekeys the same way. The difference is access. On a modern bored lock the cylinder comes out with the lockset; on a mortise lock the cylinder is threaded into the case and held by a set-screw in the door edge, so it has to be unscrewed out before you can touch the pins, and screwed back with the cam in the right orientation or the lock will not operate at all.

The cylinder thread is the other thing to know: 1 inch or 1 1/8 inch diameter, typically 32 threads per inch. Get that wrong when buying a replacement and nothing will seat.

None of this is exotic, but doing it without the follower is the classic way to end up on the floor picking up top pins.

• A flat screwdriver that fits the set-screw in the door edge without chewing it.
• A plug follower matched to the cylinder diameter. A wooden dowel cut square to length will do at a push.
• A pinning kit for the manufacturer, or the bottom pins you need out of it, plus spare springs.
• Tweezers and a pinning tray or a folded sheet of paper, so the stack you removed stays in order.
• The new key, cut before you start, and the bitting chart for that manufacturer.
• A cam screwdriver or the correct cam if you are changing cylinder type as well.

Work over a tray or a towel, not over a hardwood floor with a floor vent in it.

The old key still turns. Almost always a top pin from the previous combination that got reused, or a bottom pin one increment too shallow, so the original key can still lift that stack to the shear line. There is no partial fix: strip the cylinder and re-stack it.

The cam is on wrong. The lock will feel fine in the hand and do nothing in the door, because the cam is not reaching the case mechanism. Take it back out and reorient the cam rather than forcing the key.

A third, less common one: over-tightening the set-screw and binding the cylinder threads. It only needs to stop the cylinder unscrewing, not clamp it.

Do it yourself on a spare door, a storeroom, or anything where being locked out for an afternoon is an inconvenience rather than an incident. Call somebody when it is not.

• A commercial or shared entrance. A rekey that goes wrong on a building entry door locks everyone out, and that costs far more than the rekey.
• A restricted or high-security cylinder. Schlage Primus, Mul-T-Lock and Medeco use sidebar, finger or telescoping pins and proprietary tooling, and the pin sets are not sold without authorization. That is dealer work by design.
• Several doors at once. Keying a set of cylinders alike is where a bench and a pinning kit stop being optional.
• You do not have the bitting chart. Guessing depths is how the old key survives.

A locksmith rekeys a standard cylinder for $25-$45 and a high-security one for $60-$120, keys included, and it is a bench job of a few minutes rather than an afternoon. Prices and booking are on lock rekey in Vancouver. If the case itself is worn out rather than the keying, see lock change in Vancouver, and if the cylinder is restricted see high-security locks.

You can also bring the cylinder to the shop at 4105 Macdonald St, Vancouver, BC V6L 2P1 and skip the service call entirely. Directions and hours at contact.

Can I rekey a mortise lock without taking the cylinder out?

No. There is no top-loaded service access on a mortise case the way there is on some modern bored locks. The set-screw releases the cylinder, the cylinder unscrews, and the work happens on a bench.

How long does a mortise rekey take?

A locksmith with the pins and a bench does it in well under half an hour. A first attempt at home is realistically an hour or two, most of it spent finding pins on the floor and re-stacking.

Can I rekey a Schlage Primus or Mul-T-Lock mortise cylinder?

Not at home. Those platforms use sidebar, finger or telescoping pins with proprietary tooling, and the pin sets are only supplied to authorized dealers against the key card. That is the point of a restricted system.

Why does the old key still work after I rekeyed it?

Either a top pin from the old combination was reused, or a bottom pin is one increment too shallow, so the original key still lifts that stack to the shear line. Strip the cylinder and re-stack it.

What does a locksmith charge to rekey a mortise cylinder?

$25-$45 per standard cylinder with keys included, or $60-$120 for a high-security cylinder. Bringing the cylinder to the shop avoids the $75 service call.

Do I need a new cylinder, or just a rekey?

A rekey if the cylinder turns smoothly and only the key list is wrong. A new cylinder if the plug is worn, cracked or drilled, or if you are moving up to a restricted keyway.