Regulating your clock is the act of making repeated adjustments to your clock with the intent of achieving a desired affect, that is, making your clock a more reliable timekeeper.

Three things will affect the running of your mechanical clock, environment, friction and neglect. In this blog I will focus on friction & environment. Neglect is simple. If you don’t take care of it, it won’t take care of you.

Preparing to wind a clcok using a winding crank
Preparing to wind a clock using a winding crank


Let’s begin with friction. Every moving part of a clock must be in good condition. The gear train must be free to move but any excess friction will have an adverse effect on the running of your clock. Therefore, lubrication on a regular basis is essential. Friction leads to wear and wear leads to expensive and time-consuming repairs. Over time bushing wear will accelerate and your clock will stop.

Lubricating your clock once a year is a good practice

Six bushings on back plate
Six bushings installed on the back plate of a Sessions Westminster A mantel clock movement
Close-up of bushing wear
Close-up of bushing wear; the pivot hole is oval when it should be circular

Lubricating your clock(s) once a year is a good practice. Once the oil is used up or dries out the clock continues to run but the wheels are running without lubrication in their pivots holes. Once the pivot holes are enlarged (see above) the gears begin to run too deep into each other and the clock eventually stops. Once wear enters the equation, winding the springs do nothing as there is not enough power in the springs to overcome friction in the gear train. This leads some owners to believe that the clock is stopping because it is “over-wound” when in fact it is simply worn out. It bears repeating that preventive maintains mitigates costly repairs.

It bears mentioning that black or green oil around or in the pivot holes is a indication that re-oiling will be ineffective

Servicing a clock is a separate topic altogether but black or green oil around or in the pivot holes is a indication that re-oiling will be ineffective and dis-assembly and cleaning of the movement becomes absolutely necessary.


Changes in the ambient temperature of your environment will affect it’s timekeeping rate. It is quite common to make seasonal adjustments to your clock. If you are in a temperate climate like my part of the world, humidity and temperature changes have a noticeable effect on the rate-keeping of any clock. Increasing the ambient temperature will slow it down, from the expansion and lengthening of the pendulum rod (unless it has a compensating type pendulum).

pendulum bob with adjuster
Pendulum bob with regulating adjustment

Turning the rating screw clockwise shortens the pendulum (faster) and counterclockwise to lengthen (slower)

Regulating a clock often means making incremental changes to the length of the pendulum by means of a rate adjustment screw located at the end of the pendulum, or as in the case of a French clock pendulum (above) a rating screw inside the bob. Turning the rating screw clockwise shortens the pendulum (faster) and counterclockwise to lengthen (slower). Usually one full turn of the screw means adding or subtracting a minute per week. Some clocks have a rate adjustment arbor on the dial, typically at the 12 o’clock position.

Rate adjustment arbor
Rate adjustment arbor

If you have a double-ended key the smaller end is used for the rate adjustment arbor. “S” (slow) and “F” (fast) correspond to the direction to slow or speed up the clock. Clocks will often have one or the other but sometimes both as in this French shelf clock.

French mantel clock
French mantel clock

Rate adjustment is a trial and error process and typically takes a week or two. However, you will gradually learn the kind of adjustments required to regulate your particular clock.

A note on mainspring power and regulation.

When winding a clock you are winding a sturdy coiled metal spring. The mainspring is an energy storage system or a power source. When you turn the key the winding gets tighter until you cannot turn the key any further. This stored energy is now ready to be released but because a clock has reduction gears and an escapement (method for energy to escape) the energy is released at a steady and controlled rate. The purpose of the gear train is to convert the slow rotation of the main wheel into the faster rotation needed to tell the time. Each wheel in the train turns faster than the previous one.

A spring driven clock tends to release most of its energy at the beginning of a cycle and releases less energy towards the end of it’s winding cycle which is typically an 8-day period. Most clocks will run longer than eight days but will lose more time as the spring supplies less power.

Sessions Beveled No 2 tambour style clock and French carriage clock
Sessions Beveled No 2 tambour style clock and French carriage clock

For example, my Sessions time and strike tambour style clock typically runs 2 minutes fast at the beginning of the week and runs about a minute or two slower at the end of the week.

one-weight Vienna wall clock
This one-weight Vienna wall clock is accurate to within 30 seconds a week

Some spring driven clocks can be difficult to regulate because of how they release their power and this may vary from one clock-maker to another. If your vintage or antique spring driven mantel or wall clock is accurate to within 1-2 minutes per week you are doing very well.

On the other hand, weight driven clocks are more accurate since they release power at a constant rate through the winding cycle.

Junghans Crispi wall clcok with compensating pendulum
Junghans Crispi wall clock with compensating pendulum

Clocks will preform better in the relatively controlled environment of a home but damp basements, window sills, bathrooms, above heating elements/vents,  garages and other humid areas are unhealthy locations for your clock. Not only are harsh environments hard on the movement but the case/cabinet will suffer the ill effects of cracks, fading, detached veneer and so on.

Prolonging the life of your clock is a combination of good maintenance and common sense. Environment and friction are but two elements every clock owner should consider. Neglect or doing nothing will only accelerate clock issues.