Tag: clock oil

Top Reasons Your Mechanical Antique Clock Runs Slow: Tips & Fixes (2025 Ed.)

We are quite accustomed to the accuracy of quartz clocks which lose or gain mere milli-seconds per week. Contrast that with an era when folks were content to accept that their mechanical clock would be a minute fast or slow through the week, and it was a common practice to make small adjustments over the run cycle of a clock.

Clocks generally fall into four categories: quartz, electro-mechanical, electric, and mechanical. In this discussion, we’ll focus on mechanical clocks—whether antique or vintage—as we explore the common reasons why a clock may run slow.

Our discussion on why a clock runs slow should be grounded in a few practical realities. A typical American spring-driven clock, even when properly serviced, may gain or lose a couple of minutes per week—this is considered normal. In contrast, weight-driven mechanical clocks that vary by only a few seconds per week are regarded as highly accurate, with astronomical regulator clocks being among the most precise of all.

That said, how many mechanical devices do you know run perfectly (relatively speaking) after 120 years?

A clock runs slowly for a variety of reasons.

Let’s consider several factors and examine each in detail.

  • Environmental factors
  • The pendulum is too low or too high
  • The pendulum is the incorrect weight
  • Incorrect suspension spring length
  • The suspension spring is not attached correctly
  • Lack of lubrication
  • Gummed-up lubrication (over-oiled)
  • Balance Wheel Requires an Adjustment
  • A weak mainspring
  • Changes or Alterations During Servicing
  • Clock cycle time variance
  • Slipping, Binding and Rubbing
one-weight Vienna wall clock
One-weight wall clock with a large pendulum bob and rate adjustment on the bottom

Environmental Factors

Mechanical clocks are subject to a number of environmental factors that may cause them to gain or lose speed over the course of a year. These factors include heat, cold, and humidity. Increasing the ambient temperature of a clock will slow it down from the expansion and lengthening of the pendulum unless the pendulum is a compensating type using Mercury or dissimilar metal rods. Denser air also causes the pendulum to move more slowly.

Ogee clock showing replacement pendulum bob
Ogee clock showing replacement 1 oz rate adjusting pendulum bob

Moving a clock from sea level to a higher elevation will affect the speed of the clock.

It is common to make seasonal speed adjustments on a clock that does not have a compensating pendulum.

Numbers on bob correspond with the movement
Pendulum bob with inset rate adjustment

Pendulum Too Low or Too High

The lower the pendulum bob, the slower the clock will run. Many pendulum clocks can be adjusted either by a set screw at the bottom of the pendulum or by an inset screw on the pendulum.

In the absence of an adjustment on the pendulum, there is a regulator on the clock face. Use the small end of a double-sided key and insert it into the dial face of the clock to speed up or slow down the clock.

Shortening the pendulum will speed up the clock. Anything that increases the length of the pendulum will reduce the rate of the pendulum and result in a clock that will run slower.

Parts of the clock related to the pendulum
Parts of the clock related to the pendulum

Pendulum is the Incorrect Weight

If the pendulum is too heavy, it causes the centre of gravity to be too low, consequently, the clock will run slower. Having the correct weight pendulum for your clock ensures smooth running.

Incorrect Suspension Spring Length

Often, when a clock is repaired by a person who has limited knowledge of the effect a replacement spring will have on the running of a clock they will occasionally install an incorrect length or thickness of suspension spring. Choose the suspension spring that is correct for your clock.

Rate adjustment under the 12. Use the small end of the double-sided key to make the adjustment

Suspension Spring Not Attached Correctly, or Bent or Twisted Spring

The suspension spring is located at the top of the pendulum rod and serves as the flexible part that allows the pendulum to swing. It connects the top post to the pendulum leader. If it is not installed securely, the pendulum may not swing at all or could wobble, which robs the movement of its energy.

If the spring is bent or twisted, the imperfection will also drain its energy. This imperfection reduces the efficiency of energy transfer to the pendulum, causing it to lose amplitude and making the clock run slow or stop altogether.

Lack of Lubrication

Pivot holes that have dried up mean that there is no lubricating barrier between the pivots and their bearing holes, although the movement may otherwise be very clean.

Small drops of clock oil applied to the dry pivot holes will ensure the clock runs well and will have a long life. Without oil, the steel pivots will wear the brass pivot holes, resulting in wheels that will not mesh properly, eventually stopping the clock.

An approved clock oil must be used, although I have heard that synthetic oil works well too.

Note: a small drop of oil in each bushing hole is all that is required. As they say, Less Is More!

Gummed-up Lubrication

Clock oil loses its viscosity over time. Aging oils also lose their adhesive properties. Oil becomes oxidized, and oxidized oil forms varnish-like residues or gums that can clog pivots and bushings, increasing friction.

When a clock runs slowly, the first instinct is to apply more oil. Old blackened or greenish oil in the pivot holes is a sure sign the clock has been over-oiled or the oil has degraded. The addition of fresh oil produces an almost immediate improvement in the running of the clock, but it will not be long-lasting. In a short time, the clock will begin to run slowly again as the new oil mixes with the dirt and grime in the old oil. When this occurs, the oil becomes an abrasive paste, resulting in exacerbated wear.

The only solution is servicing, which includes disassembly, cleaning of the movement, addressing wear issues, reassembly, and testing.

Balance Wheel Requires an Adjustment

Balance wheels can be adjusted to speed up or slow down a clock.

Regulation of the escapement is done by sliding the two small weights attached to the center of the balance wheel inward to make the clock run faster, and outward to slow it down.

To adjust, simply hold the wheel and push the small adjustment “finger.” Moving the finger to the right will speed up the clock, and moving it to the left will slow it down. Each movement of one dot typically changes the rate by about 10 seconds per day.

The movement usually has a directional indicator guide near the balance wheel, with an “S” for slow and an “F” for fast.

Balance wheel escapement

A Weak Mainspring

Often, the mainspring you will find in your antique clock is the original one(s). The steel used at the time the clock was made was generally of higher quality than the steel used today, with some exceptions. By their very nature, mainsprings become weak over time.

Weak mainsprings are called “set” mainsprings. If “set”, your clock will not run a full cycle, 8 days for eight-day clocks, a full 30 hours for one-day clocks, or whatever the designed cycle. When a spring-driven clock is brought in for a professional repair, the mainsprings are often replaced.

Most properly serviced clocks with their original mainsprings will complete their full cycle, even if the springs are not as powerful as they once were, because cleaning reduces resistance throughout the gear train.

If your clock requires a mainspring replacement, a correctly sized, quality American- or German-made mainspring should provide years of reliable service.

Changes or Alterations During Servicing

Changing or altering the mechanism, such as replacing a gear with an incorrect tooth count, may speed up or slow down a clock. Although movement parts may appear to be similar, manufacturers often made small changes, resulting in parts that may not be interchangeable with the exact movement over the years.

Clock Cycle Time Variance

American spring-driven eight-day clocks typically run slightly faster at the beginning of their cycle because they provide most of their power early on, then run more slowly throughout the week as the mainspring unwinds. A spring-driven clock that is one or two minutes fast at the start of the week may often be a minute or two slow by the end of its cycle. This is considered normal, and no adjustment is necessary.

Occasionally, you will see Geneva Works or stop works on a clock movement. These mechanical additions are designed to compensate for the variance of spring power by utilizing the mechanism to limit the mainspring’s unwinding, ensuring a consistent amount of power is delivered throughout the clock’s running cycle. I have also seen enough of these clocks with the Geneva stops removed. Why? Often, the repairer did not understand how to set them!

The power on a weight-driven clock, on the other hand, is constant, and the loss or gain in time at the beginning of the cycle will be the same at the end, assuming no wear issues are slowing it down.

Slipping, Binding, and Rubbing

If your clock is losing many minutes per day, something in the mechanism is slipping or binding. If your clock is losing minutes per day after all adjustments are made, it is likely that bushing wear or some other worn component, including a weak mainspring, is causing the problem.

Clock repairers often use a term called end shake. End shake allows freedom of lateral movement for each of the wheels between the movement plates. If the plates are tight and there is no end shake, too much resistance will slow a clock. It is why clock repairers always check for sufficient end-shake when servicing the wheels/gears on a movement.

If a wall clock is not mounted correctly, the pendulum might rub against the case. Make sure the clock is not only level and in beat but also properly aligned vertically against the wall. If a clock is not aligned vertically, the pendulum may not swing evenly, causing it to rub against not only the clock case but other parts as well. This uneven motion puts extra stress on a distorted suspension spring.

Final Thoughts

Your situation may be unique, and if it is not covered by this article, I recommend consulting a clock repair expert. If you have little experience and choose to work on an antique or vintage clock yourself, the mistakes you make could be irreversible. For beginners, there are many reputable books and online forums dedicated to clock repair that can provide guidance before attempting any work.

There is also a certain element of risk working with mechanical clocks, as the power contained in the mainsprings may cause serious injury if not handled properly. Always take proper precautions when handling mainsprings or winding mechanisms. If you are unsure or unfamiliar with safe procedures, it’s best to seek assistance from a professional clockmaker to avoid injury and damage to the clock. That said, the safest clocks to work on for beginners are weight-driven ogee clocks or time-only, spring-driven clocks.

Knowing why your clock runs slowly is the first step in diagnosing the problem. Addressing the issue is the next step. Beyond that, periodic maintenance and servicing with quality parts is the key to a long life for your clock.

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How to Prolong the Life of Your Mechanical Clock

It is uncommon for a mechanical clock to run 25, 30 years or more with nothing more done to it other than the occasional oiling. I recently received a letter from someone who had taken his clock to a repair shop, where he was quoted a high price (in my view) for the repair and told that the clock would be guaranteed for 30 years. I wonder if the repair shop would be prepared to honour that guarantee after all those years, assuming they were still in business. In any event, most reputable repair shops would not offer more than a year’s warranty.

The movement was serviced and the case refreshed for this Mauthe box clock

In this post, I will discuss what it means to service a mechanical clock and explore some of the factors that influence how long a clock’s movement will last and how to prolong its life. Those factors will help you decide the best service interval for your antique or vintage clock.

Key Things I Look For

Normally, the clocks in my collection are inspected on a 3-4 year cycle. I remove the movement from its case, check its condition, and if dry, re-oil it. If I notice a particular clock stops occasionally and I find the need to investigate, I will service it simply as a prudent measure. Clocks that stop occasionally are sending a clear message that they require your attention.

This movement had just come out of a clock case and to be serviced

While the movement is out of the case, I inspect it closely, paying particular attention to the condition of the oil around the pivot holes. If there is no oil in a pivot hole, I may simply re-oil the movement. However, if I observe green or black residue around the pivots, it indicates a more serious problem. At that point, dirt and other contaminants have mixed with the clock oil to form an abrasive paste. This paste acts like a fine grinding compound, gradually wearing away the brass in the pivot holes and scoring the steel pivots themselves. In the early stages of residue buildup, there may be little wear, and the movement, once disassembled, may not require re-bushing.

Left unchecked, friction can lead to oval-shaped holes and eventually, a clock that stops running altogether.

A Clock’s Environment

I have addressed this subject in a previous article, which you can find here.

Common Reasons Why Clocks Stop—and How to Diagnose Them

Spring-driven time and strike clocks typically exhibit more wear on the strike side pivots due to the stop-and-start action of the hourly striking action.

Occasionally, I come across a movement where one side is much more worn than the other. I recently worked on a movement that required six bushings on the time side but none on the strike side. A previous owner was evidently bothered by the striking sound, leaving the strike side unwound. The sound of a striking clock is bothersome to some, especially in the early hours of the morning during a restless night. Getting used to a clock chiming or striking through the night can take time.

Inspecting a mainspring

Here, we’ll distinguish between striking and chiming clocks. A striking clock simply strikes—always on the hour to indicate the time, and often once on the half hour. A chiming clock, on the other hand, plays a musical sequence on each quarter hour and strikes the time on the hour. Quite often, people describe a clock as chiming when, in fact, it only strikes.

With chiming clocks, the chime train is first to respond to additional friction caused by dried oils and dirt. The additional complexity of the chime side means that more parts are subject to wear. The chime will eventually slow down and then stop altogether.

If I notice that I am not getting full power during the clock’s designed running cycle, I will investigate. For example, if a clock consistently stops at day 4 or 5 of its eight-day cycle, this tells me that the movement is either very dirty or there are very worn parts causing the clock to stop prematurely. Beyond that, another culprit is a weak mainspring. I do not routinely replace mainsprings, but it is a common practice among professional clock repair persons.

If your weight-driven clock stops before its designed cycle, check for twisted cables around the winding drum. Another issue is sympathetic vibration when the clock stops as the weights descend. As the weights descended to the level of the pendulum, a harmonic phenomenon occurred that is defined as “a formerly passive string or vibratory body responding to external vibrations to which it has a harmonic likeness”. Simply put; the power that drives the pendulum is now also being used to swing the weights; the pendulum doesn’t receive its full share of energy and eventually stops.

Scottish tall case clock
Sympathetic vibration has been an issue with this Scottish tall case clock

Otherwise, a weight-driven clock does not tolerate pivot wear well and will need to be taken apart to investigate for that and other possible issues.

Is the clock in beat? An out-of-beat clock will struggle to run or not run at all. Check that you can hear a steady tick-tock when winding your clock, and level the case as necessary.

I have found that different clocks have different levels of wear tolerance. It doesn’t take much wear to stop a German movement, whereas American time-and-strike clocks will tolerate pivot wear and still run reasonably well, even when very worn.

A kinked suspension spring, or one that is too stiff or the wrong size, can affect the oscillation of the pendulum.

A clock that will not run when the mainsprings are fully wound is often thought to be ‘overwound.’ The term ‘overwound’ is a myth, although it’s true that a tightly coiled spring, fused by old oil and dirt, might give the appearance of being overwound. Again, the clock must be taken apart, and while the mainsprings are being thoroughly cleaned, the entire movement must be seen to as well.

Quite often, I encounter clocks whose movements have been removed so many times that the mounting screws have become loose. This can be addressed by using slightly larger screws or by filling the screw holes before reusing the original screws. If left unaddressed, however, the movement can become unstable. A movement that is not properly secured in the case may shift, become misaligned, and put the movement out of beat.

Sometimes, an unusual problem may occur when the clock stops at the exact time every 12 hours. Check that the minute and hour hands are not interfering with each other.

Servicing a Movement – What Does It Mean?

How often should a mechanical clock be serviced? It is not as simple an answer as it seems.

If your clock does not work, cleaning it is the first step in determining the problem. Cleaning is just another word for servicing, and the term “servicing” in the realm of professional clock repair implies a complete tear-down of the movement.

Though it was a common practice in the past, dunking a movement in solvent and hoping for the best is not a substitute for proper servicing, nor is spraying the clock all over with lubricant. WD-40 is a favorite among novices, but it is not a true lubricant—it’s a water-dispersing agent.

Servicing a clock involves the following 13 steps:

  1. Removing the movement from its case,
  2. Let down the mainsprings (if present),
  3. Assessing the movement,
  4. Disassembling the movement, taking photos, or making notes,
  5. inspecting the parts carefully,
  6. Cleaning the movement either with an ultrasonic cleaner or by hand,
  7. Addressing any wear issues and repairing damage caused by abuse or failed parts.
  8. Reassembling,
  9. Oiling selected components,
  10. Running the movement on a test stand,
  11. Readjusting if necessary,
  12. Reinstalling into the case and,
  13. Re-adjust if necessary

There is no substitute for a complete tear-down of the movement.

Caring for a mechanical clock means more than just winding it and hoping it keeps time. Regular inspection, proper servicing, and attention to signs of wear can go a long way in keeping your clock running well for years to come. Understanding what your clock needs—and when—will help you preserve both its function and its value.

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New to clock repair? Here are some errors to avoid

Clock repair and restoration can be a rewarding yet delicate process, requiring both skill and patience. Whether you’re working on an antique clock or a vintage movement, there are several common pitfalls that can easily derail your progress if you’re not careful. From handling mainsprings to ensuring proper oiling, small mistakes can lead to bigger issues down the road.

In this article, we’ll explore some of the most frequent mistakes made during clock repair and share tips on how to avoid them, ensuring your repairs are both successful and long-lasting.

Mainsprings

When working with mainsprings, always be cautious about how they are stored and handled. If two mainsprings are placed on top of each other, they may mate together in a way that makes it nearly impossible to separate them without damaging the springs. To avoid this, always position them so that they wind in opposite directions. This ensures they cannot interlock and will be easy to handle separately when the time comes.

Orientation of the Count Wheel

The count wheel plays a critical role in regulating the striking sequence of a clock. Different movements may have count wheels that rotate in opposite directions, so it’s essential to remember or note the orientation of the count wheel when removing it. If you fail to mark or track which way it goes, you may end up installing it incorrectly, which can result in malfunctioning strikes. Always take care to note the direction of rotation when removing any component like this.

Broken pressure washer on the count wheel

Helper Springs

Helper Springs may look like an add-on but are part of the original manufacturing process. Novices are tempted to leave them out when servicing a clock reasoning that they were added later during a repair.

Helper springs are vital for the correct functioning of certain levers and gears in a clock’s movement. If these springs are not properly attached, the levers may fail to operate as they should, and the springs can even interfere with other components, preventing them from working as intended. Make note of the orientation of the helper springs during disassembly and always check that all helper springs are in place and attached securely before reassembling the movement.

Removing lever with helper spring

Take Special Care with Pivots

Patience is key when working on clock movements. If pivots are difficult to fit or the plates don’t seem to align correctly, it’s tempting to apply more force. However, applying too much pressure can bend or damage the pivots, which may be difficult to fix without professional tools or techniques. Instead of forcing components, carefully assess the situation, ensure everything is aligned, and use minimal force to avoid damaging the pivots.

An especially designed pivot locator can be your best friend.

Pivot locator

Think twice before concluding a part is defective

It’s easy to jump to conclusions when diagnosing problems with a clock movement. You might assume that a part is defective or not functioning properly, but this is often not the case. Before replacing any parts, make sure you have thoroughly inspected the movement and confirmed that the part is indeed damaged or worn. Assumptions can lead to unnecessary replacements, costing both time and money. Always verify before proceeding.

Taking photos is a best practice

Taking pictures during disassembly is a common practice, but there’s a risk in doing this too early. If you take pictures before thoroughly understanding how the clock is put together, the images can become a source of confusion later on. You may forget specific orientations, parts, or connections, leading to problems when reassembling the movement. Instead, take the time to carefully observe and document each part’s position as you disassemble the clock. This will help ensure a smoother reassembly process.

Stop and Think Before Cleaning a Dial

Many a dial has been ruined by a repairer’s eagerness to clean it. If the dial needs cleaning, consider using a gentle hand-cleaning method (soap, water and a soft cloth will do) to avoid any damage like the damage to a UM Muller clock dial below.

Dials, especially antique ones, are delicate and can easily be damaged by the high-frequency vibrations in an ultrasonic cleaner. The cleaner may strip paint, damage decals, or even warp the dial if it’s not carefully handled. Always remove the dial before placing any components in the ultrasonic cleaner.

Proceed in a Safe Manner

When disassembling a clock movement, always ensure the mainsprings are securely restrained before you separate the plates.

Clamps for mainsprings ensure safety when working on movements

If the plates are removed without securing the mainsprings, they could unwind suddenly, potentially causing damage or injury. Use a mainspring winder, clamps, or similar tools to restrain the springs before beginning the disassembly process to avoid any accidents.

When using a spring winder, it’s important to wear thick leather gloves and eye protection to safeguard yourself from potential surprises if a spring fails. These precautions help minimize the risk of injury from sudden, high-pressure releases.

Resist the urge to bend things

During repairs, it’s easy to inadvertently bend parts while trying to make them fit or forcing them into place. Parts of the striking mechanism, especially on the striking levers, are particularly prone to bending. Once bent, they can be difficult to straighten and may not work correctly afterward. Always handle parts with care, and if something does not fit easily, take the time to inspect the alignment or find the correct adjustment method rather than forcing it into place.

Over-oiling is Never a Good Idea

As a person I knew once said; “if a little is good, a lot is better”. It’s tempting to apply generous amounts of oil when servicing a clock, but over-oiling can lead to a number of issues.

Excess oil can attract dust and dirt, which will gunk up the movement and cause it to run less smoothly. It can also seep into areas where it shouldn’t be, like on the dial or outside of the movement, leaving unsightly stains. Always use an approved clock oil sparingly, and only in the areas where it’s needed. A little goes a long way, and it’s better to apply no more oil than necessary rather than risk over-oiling the movement.

To Summarize

Clock repair requires not only skill but also a cautious approach to avoid common mistakes that can lead to damage or injury. By taking the necessary precautions—such as properly handling mainsprings, ensuring parts are correctly installed, and using minimal force—you can prevent costly errors and ensure a successful repair. Patience and attention to detail, will make all the difference in restoring a clock to its full functionality, allowing it to run smoothly for years to come.

Suggestions and tips for novices? Join the conversation.

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