Just Rekeyed and Now Key Binds: Post-Service Decision Tree

Why this matters

A binding key on a freshly rekeyed cylinder is the single most common locksmith callback. The customer interprets it as "you broke my lock," even when the bind is caused by an unrelated condition that was masked by the old key. Walking a structured tree keeps you from chasing the wrong fault, protects your warranty exposure, and gets the cylinder turning smoothly without a full teardown on the doorstep. The goal is to isolate whether the bind originated inside the cylinder (pin stack, plug, cap), at the key (cut depth, burrs, wrong blank), or outside the cylinder (cam, tailpiece, strike, door sag) before you start pulling pins.

Step 1: Reproduce and localize the bind

Insert the key fully and turn slowly in both directions. Note exactly where the resistance starts: at insertion, at the first few degrees of rotation, at the cam throw, or at withdrawal. Each location points at a different root cause. Bind on insertion almost always means a pin or key problem. Bind only at full cam throw points at the tailpiece or cam. Bind on withdrawal often means a top pin is hanging up on a worn chamber edge.

Test with the bitting key, the control key (if IC core), and a known-good cut from your code machine. If only one key binds, the key is the issue. If all keys bind, the cylinder or its mounting is the issue.

Step 2: Pull the key and inspect it under magnification

Burrs from a worn cutter wheel are the number-one cause of post-rekey binding. Look at each cut shoulder for a raised lip or feathered edge. Run the key edge across a fingernail; a burr will catch. Deburr with a fine file or a stone, then retest. If you cut the key on a code machine, verify the depths with a depth-and-spacing gauge against the published chart for that keyway. A single cut one increment deep or shallow will bind a pin against the shear line.

Confirm you used the correct blank. A blank with the wrong warding profile, the wrong shoulder reference, or a near-miss aftermarket equivalent will sit in the keyway at the wrong height and force pins past their seating tolerance.

Step 3: If the key checks out, isolate the cylinder from the door

Remove the cylinder from the door (loosen the set screw on a mortise cylinder, remove the rose and retainer on a key-in-knob, pull the cap on an IC core). Operate the cylinder on the bench with the same key. If the bind disappears off the door, the cylinder is fine and the issue is mounting alignment, cam-to-hub engagement, or door sag pulling the cylinder out of square. If the bind persists on the bench, the cylinder itself owns the fault.

Step 4: Bench diagnosis of the cylinder

With the cylinder off the door, work through these checks in order:

• Plug rotation without the key: spin the plug with a follower. It should rotate freely with no high spots. A tight spot means a chamber burr or a swollen plug from over-tightening the cap.
• Pin chamber inspection: pull the cap, dump the springs and top pins into a tray in order, look down each chamber for swarf, plating flakes, or a galled top edge from prior picking attempts.
• Bottom pin heights: re-measure each bottom pin against the cut depth. A pin one increment too tall holds the shear line open and binds.
• Spring condition: a collapsed or kinked spring lets a top pin sit crooked and bind on rotation. Replace springs as a set, not individually.
• Master pin stacks: in a masterkeyed system, a thin master wafer can tip and jam. Reassemble with the wafer flat and confirm with the change key and the master.

Step 5: If bench is clean, look at the cam and tailpiece

A rekey often involves swapping cams or tailpieces to match the new lockset. A tailpiece that is one notch off, a cam clocked 180 degrees from its correct orientation, or a tailpiece bent during reinstall will bind only at full throw because the cam is fighting the hub or the latch retractor. Compare against the manufacturer cam chart for the lockset family. Reinstall with the cam in the documented orientation and the set screw torqued to spec.

Step 6: Door and strike contribution

If the cylinder turns smoothly on the bench but binds in the door, the door has shifted, the strike has moved, or the latch bolt is dragging on the strike lip. Open the door and operate the key with the door open: if it turns smoothly, the deadlatch or latchbolt is preloaded against the strike and that load is transferring up through the latch into the cam. Adjust the strike, shim the hinges, or plane the door edge. None of that is a cylinder problem and rewriting it as one wastes a return visit.

References

• ANSI/BHMA A156.5, Cylinders and Input Devices for Locks, current edition
• ANSI/BHMA A156.2, Bored and Preassembled Locks and Latches
• ANSI/BHMA A156.13, Mortise Locks and Latches
• ALOA Institutional Pin Tumbler Service Guidelines