Lock case or cylinder? Two different jobs
"Changing the lock" on a steel door means two things with very different cost. Replacing the cylinder — the part the key enters — is one screw and ten minutes. Replacing the lock case means pulling the mechanism out of the leaf and fitting another of exactly the same dimensions; if the dimensions differ, the leaf itself has to be machined.
A lost key, a change of tenant, a suspicion that a key was copied: all of those are cylinder jobs. The case is only touched when the mechanism itself fails or when you are upgrading the system.
Three dimensions that constrain your choice
- Backset: the distance from the leaf edge to the cylinder and handle axis, fixed by the holes already cut in the leaf.
- Centre distance between handle and cylinder: the escutcheon is pressed to match it, so a case with a different spacing leaves your plates unusable.
- Leaf thickness: sets cylinder length and spindle length.
Measure all three before buying. Products sold as "steel door locks" are not one size, and a case with the wrong backset will not fit without cutting a finished leaf.
Keeps: the invisible half of the lock
A strong case paired with a thin keep plate performs like an average lock. Bolts throw into the frame, and under force the load lands on the keeps. They must be reinforced into the frame profile, with fixings reaching the backing rather than just the front sheet. In production, keep pockets are machined before the frame is welded; pockets cut afterwards reduce frame stiffness.
If you are upgrading, ask whether the keeps change too. Moving to a multi-point system needs new pockets at the head and threshold for the vertical bolts — possible with the door in place, but precise work.
Reading the fault before calling anyone
- Key turns hard, worse when the door is shut: the leaf has dropped and the bolts are forcing into their keeps. Adjust the hinges, not the lock.
- Key turns freely with the door open: mechanism is sound; the problem is alignment.
- Key snags halfway even with the door open: dirt, dryness or pin damage inside the cylinder. Replace the cylinder.
- Bolts throw but the door pushes open: insufficient engagement. Reposition the keep plate.
- Handle droops and does not spring back: tired spring cassette. Repair or replace the case.
Upgrade in the right order
Spend from the weakest link outward. The usual sequence: cylinder first, with anti-snap and anti-pull protection and a reinforced escutcheon; then keep plates; then hinge-side security pins; and only then a multi-point case. Doing it in reverse puts money where it shows and leaves the vulnerable part untouched.
Buying a new door settles the question at source, because lock configuration, leaf thickness and keep pockets are designed together. On wide leaves, three-edge locking is what stops the centre of the leaf flexing, which is why it is standard across our building entrance doors. On apartment doors, gasket continuity and a square leaf matter as much as the lock itself; within luxury steel doors the same pattern can be built with different lock configurations, so choosing a model is not yet choosing a lock.
Key management and habits
In multi-unit buildings, plan the entrance and apartment key system together. A single key for both is convenient but widens the consequences of a loss. Whichever you choose, keeping cylinders within one family makes spares easier to source years later — a real consideration on export projects where the nearest stockist is in another country.
Two habits extend lock life noticeably: use the handle to close the door rather than slamming the latch home, and never put liquid oil in a cylinder — it collects dust and seizes the mechanism. Use a dry or graphite-based lubricant instead.
Lock configuration is priced per door. Send the measurements of your existing opening, or the model you are considering, and we will quote the specification with shipping from Istanbul calculated separately.
