Everything drifts out of adjustment, and almost nobody checks

These are listed in the order worth acting on, which with adjustment drift in owned products is not the order they are usually presented in.

Why settings move on their own

New assemblies settle as surfaces bed in against each other, which removes a small amount of material and relaxes the clamping force holding them together. Thermal cycling expands and contracts parts at different rates, and each cycle can leave a joint fractionally different from where it started.

Vibration causes threaded fasteners to rotate slowly under repeated micro-movements, a well-documented mechanism that has nothing to do with anyone being careless. Elastic components such as belts, springs, foams and gaskets take a permanent set over time and stop applying the force they were chosen to apply. None of this announces itself, which is why the first symptom is usually accelerated wear somewhere that was never the original problem.

Fasteners and clamping force

A bolt works by stretching slightly and pulling two parts together, so the useful quantity is tension rather than how tight it happens to feel. That tension decays through settling and relaxation, and a joint at reduced tension allows micro-movement that abrades the mating faces. Once the faces are damaged, retightening no longer restores the original condition, which is why checking early beats checking eventually.

Compared like for like, thread-locking compounds, locking washers and prevailing-torque nuts exist because plain threads in vibrating assemblies do not stay where they were put. Where a manufacturer specifies a re-torque after a running-in period, that instruction is describing exactly this process.

Alignment in things that move

Rotating and sliding assemblies are designed with parts on a common axis, and small angular errors produce loads the bearings were never sized for. A belt running slightly off line wears its edge, heats up and fails early, and the belt gets replaced while the misalignment quietly stays. Doors, drawers and lids drift on their hinges as the structure settles, and a misaligned closure loads its catch instead of its frame.

In the small print, wheels, castors and rollers that are no longer square drag rather than roll, which produces flat spots and increases the effort required. The general rule is that misalignment converts into wear somewhere, and the wear appears at the weakest point rather than at the misaligned one.

Instruments and anything that measures

Devices measuring weight, temperature, pressure or level drift because their sensing elements age and their reference points move. Many consumer instruments include a calibration or zeroing procedure in the manual that most owners never perform even once. Drift is often gradual and consistent, which makes it invisible, since each reading looks entirely plausible relative to the last one.

Where a reading matters for safety, cooking, medication or a legal purpose, a known reference check is the only way to detect drift. Formal calibration regimes exist for trade and professional instruments, and the requirements differ by country and by application.

Installation that moves after installation

Appliances levelled on a floor that later settles are no longer level, and machines with rotating drums are particularly intolerant of this. Plumbed and vented connections shift with building movement and with the machine's own vibration, so a joint that was sound can weep later.

After the warranty ends, anything mounted to a wall relies on fixings whose grip depends on the wall material, and that grip can degrade with damp or repeated loading. Furniture assembled with cam fittings and dowels relaxes in the first months, and retightening once is far easier than repairing a racked frame. Because installation faults produce symptoms that look like product faults, checking the installation first saves a large number of unnecessary service visits.

Where a claim here has not been tested directly it is inference, and it should be read as inference.

Building a check into ownership

Choose a small number of checks per item, write them down, and attach them to something you already do seasonally. Feel and listen rather than dismantling, since changes in noise, vibration, effort and free play detect drift without creating new problems. Use the manual's own maintenance section as the list, because the manufacturer already knows which adjustments tend to move.

Photograph the original state of anything adjustable before you touch it, so a check that goes wrong can be reversed. Where a check requires a torque figure or a special tool, treat that as a signal to involve a repairer rather than to improvise.

Everything above, in order of what to do first

1. Why settings move on their own. New assemblies settle as surfaces bed in against each other, which removes a small amount of material and relaxes the clamping force holding them together.
2. Fasteners and clamping force. A bolt works by stretching slightly and pulling two parts together, so the useful quantity is tension rather than how tight it happens to feel.
3. Alignment in things that move. Rotating and sliding assemblies are designed with parts on a common axis, and small angular errors produce loads the bearings were never sized for.
4. Instruments and anything that measures. Devices measuring weight, temperature, pressure or level drift because their sensing elements age and their reference points move.
5. Installation that moves after installation. Appliances levelled on a floor that later settles are no longer level, and machines with rotating drums are particularly intolerant of this.
6. Building a check into ownership. Choose a small number of checks per item, write them down, and attach them to something you already do seasonally.

The takeaway

Assume every setting has moved since the day it was made, and check the few that matter.

Buy for the failure you can live with, not the feature you will use twice.