Tag: clock servicing

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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Prolonging the Life of your antique or vintage clock

New owners of an antique or vintage clock might find it surprising that their recent purchase requires periodic maintenance. This realization often dawns upon them only when the clock stops, and they struggle to get it running again.

This Junghans wall clock, C.1899 is a daily runner

In this discussion, we explore regular clock maintenance, underscoring the importance of continuous inspection to ensure your clock enjoys a long and functional life.

Determining the ideal service interval of a running clock is a frequent topic of discussion among clock repairers, influenced by various factors that impact a clock’s lifespan. Factors include environment, age, frequency of use, manufacturers recommendations, complexity of the movement, user maintenance and cost of repairs.

Regular inspection

I conduct regular inspections of all clocks running continuously in my collection every 3-5 years, enabling me to pinpoint potential issues and remediate them if necessary.

Not all of my clocks are inspected on a regular basis. Among my collection of approximately 85 clocks, only a maximum of 27 clocks remain in continuous operation. Of the remaining ones, certain clocks may need specialized maintenance, are in various states of repair, some have fragile or rare parts, and others are reserved for special occasions.

Elisha Manross steeple clock from the 1830s

As an illustration of a clock that seldom runs, one of my clocks is a 30-hour time-and-strike Elisha Manross steeple clock dating back to the 1830s. This particular clock features brass mainsprings, making them irreplaceable if they were to break today.

Brass mainsprings for Manross clock
Brass mainsprings

Clocks that occasionally stop signal a need for immediate attention. I look for any immediate issues that might have caused the stoppage otherwise I focus on identifying green or black residues around the pivots. Contaminants mixing with clock oil create an abrasive paste, damaging bushing holes and pivots and in time the wear will stop a clock. If a clock stops after running continuously for years it is more often than not a wear issue. Disassembling the movement is imperative, enabling a detailed assessment of wear and determining the extent of intervention.

When dealing with a non-functioning clock no matter what procedures you have taken to get it running, the first step involves a visual inspection to identify evident problems like broken or bent parts, as well as missing components. This leads to the next step which is called servicing. True clock servicing involves comprehensive disassembly, inspection, cleaning, addressing wear and damage issues, reassembly, and thorough testing.

Factors that affect wear

Several factors affect wear, with the local environment playing a pivotal role. Humidity and temperature fluctuations, especially in older homes or those with wood stoves, impact a clock’s performance. Dust and pet hair, infiltrating the movement, also accelerate wear.

Clock cases that are tightly sealed with access doors help alleviate these concerns, and a properly sealed clock will extend the intervals between servicing.

Gustav Becker Vienna Regulator runs continuously

Different types of clocks exhibit unique wear patterns. Spring-driven time and strike clocks often wear on strike side pivots more often than the time side due to the shock of the half-hour strike. Chiming clocks face additional challenges due to the complexity of the chime/strike sides, where dried oils and dirt cause friction, leading to eventual stops. Weight-driven clocks, especially if not correctly in beat or with twisted cables, may suffer premature stops and require thorough investigation.

A mechanical clock as a decoration

Many people appreciate the decorative allure of antique clocks and opt not to operate them, choosing instead to display them as decorative pieces. However, leaving a mechanical clock unused poses risks.

Time and the environment, rather than operation, cause the most damage. Unused clocks primarily suffer from the thickening of the oil over time and the eventual breakdown of that oil. On the other hand, dried-up oil provides no lubrication for the pivots and leads to accelerated wear. Excessive enlarging of the brass pivot holes by the steel pivots will eventually lead to depthing issues (depthing, which is the correct meshing of one gear in relation to the next is a topic beyond the scope of this article).

Parts left motionless often tend to fuse, and rust accumulates, particularly in humid environments. Although the majority of clocks possess brass plates that are resistant to rust, there is a significant portion of steel components in them that are susceptible to corrosion.

In addition, mainsprings frequently become stuck due to thickening oil, causing the spring to fuse in position.

Running the clock even occasionally such as once per month is essential, enhancing longevity.

Clock cases also need attention

While maintaining the clock movement in good condition is crucial, cleaning the antique clock case is also important for several reasons.

Firstly, a clean case enhances the overall appeal of the clock, showcasing its design and craftsmanship.

Secondly, regular cleaning prevents the buildup of dust, dirt, and grime.

Thirdly, cleaning the case helps preserve the wood or other materials, preventing cracking and blistering and ensuring its structural integrity. I apply Minwax furniture paste wax on certain surfaces to protect the finish and maintain its appearance.

Junghans Corner feet finished
A clean clock case showcases its design – Junghans Sydney mantel clock C.1913

Overall, cleaning the antique clock case ensures its longevity, functionality, and visual appeal, making it an essential aspect of proper clock maintenance.

Health check for clocks

In my controlled home environment, with stable temperature, low humidity, and no pets, I prioritize regular health checks for my clocks as a preventive measure. Yet, due to the controlled environment in my home, I can prolong service intervals to around 4-5 years.

Shorter periods are recommended for clocks in less controlled or fluctuating environments, ensuring timely maintenance and preserving the clock’s longevity. Utilizing an Excel spreadsheet, I meticulously record changes, service intervals, and issues for each clock in my collection.

My goal is to ensure every clock’s durability, preserving them for future generations, and potentially passing them (well, at least some) down to my children.

Finding a Reliable Clock Repair Professional


If you’ve acquired a clock as a gift, through inheritance, from antique shopping, online purchases, or any other means, and it’s not functioning correctly, you have several choices in having it repaired.

Seth Thomas Adamantine mantel clock, C.1909

You might decide to try fixing the clock yourself, especially if it’s a simple or inexpensive clock. Basic tools and some luck might help with minor repairs or cleaning, but keep in mind that professional skills and patience are often required for clock restoration.

Repairing clocks is a specialized craft that takes years to master, and specialized equipment is often needed. For high-quality or rare clocks, it’s often best to trust a professional.

Ingraham Grecian
Ingraham Grecian, C.1872

Clock repair is becoming a rare and dwindling profession. Many clock repair businesses are closing as older experts retire, and there aren’t enough newcomers to continue the tradition. Finding a reputable clock repair person can be challenging and may require significant time and research.

Reputable clock repair establishments hire certified professionals who possess the expertise to handle a diverse array of clocks. Meanwhile, the availability of clock repair schools is decreasing, and there are fewer graduates, which leads to very few options in some areas.

Scottish tall case clock
McLachlan tall case clock, C.1848

Suppose you’ve made the decision to search for a clock repair specialist. In that case, here are some suggestions to consider in your quest.

Finding a Reputable Clock Repair Service:

  • Perform a Google search to determine if there is a clock repair shop in your immediate area.
  • Antique stores often have connections with reputable clock repair specialists. Attending antique fairs can also help you network with enthusiasts who can recommend experienced clock repair professionals.
  • Check with the Better Business Bureau to see if a repair shop is in good standing without complaints. If you find a potential clock repair service online, be sure to read reviews and testimonials from previous customers. This can provide valuable insights into their reputation and the quality of their work.
  • Consult the National Association of Watch and Clock Collectors (NAWCC) business directory, which lists reputable repair services in several countries.
  • Join local NAWCC chapters or forums (joining is free) to connect with experienced horologists and seek guidance on finding a repair person in your area.
  • If in the UK, look for individuals with memberships in the Antiquarian Horological Society (AHS) for clock expertise.
  • In Germany, the Deutsche Gesellschaft für Chronometrie is an excellent resource for finding clock specialists.
  • When contacting a clock repair specialist, don’t hesitate to ask for references from past clients. Speaking with satisfied customers can help you gauge their expertise and reliability.
  • Seek recommendations through word of mouth from people who have had their clocks repaired by reliable professionals.
  • Although not all watchmakers work on clocks, some may have the expertise or know of clock repair specialists in your area. Consider reaching out to watchmaking shops for referrals.
  • Contact local museums or historical societies that exhibit clocks. They often collaborate with or have connections to skilled clock restorers who can help maintain their collections.
  • Ensure that the repair person has the necessary qualifications and certifications, especially if you have a valuable or antique clock that requires delicate handling and expertise. You will feel more comfortable knowing it is in trusted hands.
  • If possible, visit the clock repair shop or specialist’s workshop in person. This gives you an opportunity to see their work environment, tools, and the types of clocks they are currently servicing.
  • Once you have found a clock repair individual get an estimate of how long the repair is expected to take. Complex repairs may require more time, so it is essential to have a realistic time frame in mind. Count on a turnaround time of months rather than weeks even for standard servicing.
Kienzle World Time clock
Kienzle World Time clock, C.1951

Whether you’ve come into possession of a clock through various means, finding a skilled clock repair specialist is essential to restore your clock to its former glory. While attempting DIY repairs can be tempting for simpler clocks, the intricacies of clock mechanisms often demand the expertise of a professional.

Complicated repairs are beyond the scope of the do-it-yourselfer

By following these guidelines and conducting thorough research, you can locate a reputable clock repair specialist who will provide the care and attention your clock deserves, preserving its beauty and functionality for years to come.

Should mainsprings be routinely replaced on an antique clock when servicing?

Mainspring barrel

A mainspring’s purpose is to provide motive power for the wheels to move in a clock train. All mechanical clocks require a power source and the power source may be by weight or spring. Mechanical clocks that have mainsprings will have one, two, or three winding points which, once wound provide power for a clock’s designed cycle.

Each winding point or arbour is located on the dial face and requires a key (one key fits all arbours) to wind the clock. The mainspring is rated to provide power for a clock’s designed cycle, whether it be 1-day, 8-days, 15-days, and so on.

Sessions mainsprings cleaned and ready to be re-installed in the movement

Mechanical clocks are machines and over time machines wear out. When a clock will not wind up, it is time for a service. The service can be done if you have the skills and equipment otherwise you must depend on a professional clock repairer.

Should mainsprings be replaced during routine servicing?

Though not in the clock repair business I am aware that some repairers routinely replace mainsprings and, of course, the cost is passed on to the customer. Should they be replaced on a routinely or only when necessary?

As a general rule, I do not replace mainsprings when servicing a mechanical clock unless there is something fundamentally wrong with the spring(s). Obviously, there are situations where a mainspring must be replaced when it has failed in some catastrophic manner.

Broken mainspring for barrel
Broken mainspring which is not saveable

There may be occasions when there is too much surface rust or stress cracks on the mainsprings which will make them susceptible to failure and/or seizing and the prudent course of action is to replace them.

Ansonia time-only movement – Too rusted to save?

However, repairers reason that new mainspring(s) will extend the period between servicing and provide additional insurance for the repairer so that if the clock stops soon after servicing, issues other than the mainsprings are suspect.

Mainspring servicing
Mainspring servicing

New quality mainsprings (American or German) also provide more power than the springs they replace and more power means they will continue to provide sufficient power for the clock through its rated cycle even if very worn.

Installing or punching a bushing
Addressing wear by punching in a new bushing

The original mainsprings are often of better quality than a new spring. They may not have as much power as a new mainspring but many clocks, despite the fact that they are over 100 years old have springs that have more than sufficient power.

Once the movement is thoroughly cleaned, the pivots are polished and pivot wear is addressed there is less friction on the moving parts and therefore less power is required to drive the movement through it rated cycle.

Mainspring that is not salvageable

What if there are minor issues with the mainspring?

There are certain situations where a broken mainspring may be salvaged if the break is at the hook or loop end but not if it is broken in the middle. The mainspring can be shortened by two or three inches and after the repair, the spring will continue to provide sufficient power for the clock to run through its cycle.

What to do if your clock requires servicing by a professional

Should you bring your clock in to be professionally serviced ask plenty of questions. If it is recommended that the mainsprings be replaced, ask why, specifically. Once you receive a satisfactory explanation proceed with the repair.

New mainsprings, when the cost is upwards of $25 for each mainspring, will add substantially to the repair cost, something to be considered if the clock has little value. Of course, if it is to be repaired for sentimental reasons the cost is immaterial.

Mainsprings need not be replaced simply because they are old and “tired” and it does not require a lot of power to run a mechanical clock if serviced correctly.

Your choice!

Servicing a Seth Thomas 8-day movement

A marriage of Waterbury and Seth Thomas

I was attracted to the style of this clock but disappointed when I learned that it was a marriage of a Waterbury case with a Seth Thomas movement. Briefly, a marriage is when parts from two different makers come together.

Buying a clock from a flea market, antique mall, a shop or what have you is always a gamble. On this particular clock there is no trademark or name on the dial or a label in the back of the case that told me who the maker was. I made an assumption and it was an impulse buy.

Glass and bezel are from a later clock

While at the antique store I opened the back of the case to confirm that the clock had a movement and it was complete with pendulum bob and coiled gong and to me everything appeared correct until I brought it home. My first thought was an Ansonia movement when I looked at it under the dim light of the store.

Seth Thomas and other makers made similar cabinet style cases but this is the Wren by the Waterbury Clock Company. Being a marriage, the clock is worth much less to those particular about such matters. No matter, it looks attractive.

I can imagine a past owner’s conversation with the repair guy, I don’t care what you do, just make it work! And the repair guy responds by removing the very worn Waterbury movement and replacing it with a Seth Thomas. Easy peasy!

One of the current seller’s stickers on the case said it was a non-working clock but with minor adjustments, such as moving the pallets closer to the escape wheel and releasing the time-side mainspring, I had it running in no time. There is not much wrong with the movement and a good cleaning plus a bushing or two should put things right.

So, what did I buy?

As I said, I like the case and it has a decent movement but when a clock is a marriage one can expect some questionable repairs and interesting changes as one takes things apart.

I am not absolutely certain the dial pan came with the case or was added later but the glass and bezel are certainly from a mid-century mantel clock. It is so ugly it will be tossed into the spare parts drawer. I will keep the dial pan but a piecrust bezel with flat glass is more appropriate for the period.

Piecrust dial on a 6-column mantel clock
Seth Thomas time and strike 8-day movement

I removed the dial and discovered a number of extra screw holes here and there, varying lengths of screws, some screw holes filled with pieces of wood, even a couple of Robertson screws (not invented until after the First War) and so on. Obviously the replacement movement required new holes and why not drill a few extra holes for good measure!

The hole on the dial just above the 12 is larger than it should be. It was either enlarged to accommodate the regulating arbour or it’s a new hole altogether.

On a positive note both the case and the movement are from a similar period.

Disassembling the movement

But this post is about servicing the movement.

I am impressed with the engineering of this Seth Thomas movement. It is robust and well-designed though it has an interesting, overly complicated, speed regulating feature.

From my research I found that the hip style movement is the type 44 which was used for a 12 year period beginning in 1890. In 1903 it was presumably replaced with the type 89 movement, simpler to manufacture, fewer parts and more reliable, and appeared in many thousands of ST mantel clocks afterwards. It has a sickle shaped brass piece between the plates so that the clock can be turned backwards repeatedly at the hour to sync the strike with the hands. It is technically called a set-back counter weight.

Brass piece indicated by arrow
Regulating arbour with worm gear on one end

There were variations of this movement, front winding movements as opposed to rear winding, with and without the worm gear speed regulator and some with stop works. This movement does not have Geneva stops.

It took me more time than usual to pry open the plates because I was slowed down by the intricacy of regulating mechanism. Part of the mechanism consists of a long arbour that passes from the front plate to the back plate. At one end is a worm gear and on the other is the regulating end. It is secured to the outside of the front plate by means of a spring with a pin through the arbour. To release the arbour, the pin must be pulled and the spring releases.

Well, actually the spring flew across the room. No problem, I’m used to crawling on the floor looking for clock parts.

I have worked on a lot of American time and strike movements but this type of regulating mechanism is a first for me. In fact, the set-back counter weight is also a first for me.

Analysis of the movement

The movement has had 12 bushings installed, 5 on the front plate and 7 on the back. The work is well done but I don’t like the arrows scratched into the plate indicating where each bushing would be installed. I use a Sharpie pen and after I have completed the bushing work I wipe the marks off with alcohol. There is no need to mar the plates.

Arrow indicating scratch mark below bushing

After looking over the movement carefully I can see there is enough wear in some bushings that they must be replaced, both second wheels, front plate, the governor, both front and back and the escape wheel bridge bushing which for some reason has punch marks around it, the only unsightly repair.

Escape wheel and bridge

The mainsprings look to be in good shape and still bears the original ST trademarks. No worn gear teeth and the pivots, plus the lantern pinions are all in great shape.

All in all, not bad for a movement that was last serviced quite a number of years ago.

Strike side of ST movement

The pivots were polished and next is the bushing work. Two were interesting to say the least.

The count count wheel and the strike pin wheel are side by side. A bushing was required for the pin wheel but I could not access it from inside the plate. This is one of those few times when drilling from the outside is the only way however, I was able to push the bushing home from the inside plate. It is one of those situation where you have to stand back, analysis the problem and consider a strategy. It worked.

The second was the escape wheel bridge. To stabilize the bridge a 5-step block jig comes in handy. Otherwise, it is very difficult to keep the bridge steady and drill a straight hole.

Ingraham Grecian
% level job block used for an escape wheel bridge

The drilling went fine until the last 3.47 mm cutter. When I began to drill out the hole the old bushing came out. I knew right away that the new bushing would not have a tight fit. Evidently a past repairer had the same problem.

staking set
staking set

The block from a staking set is a useful tool. With it I was able to lay the plate down on it and punch the bushing from the inside to stabilize it.

Once together everything fell into place or so I thought. Unfortunately, I will have to take it apart again because I forgot the regulating worm gear which can only be installed with the plates separated. The movement will run perfectly fine without it, but it is part of the clock.

In the meantime the movement is running well.

A marriage of two makers, Waterbury and Seth Thomas

This clock is an antique store find not too far from where I live. It was high on a shelf and the price was not visible. I asked the shopkeeper to take it down so that I could check the price ($40) and verify that it had a mechanical movement.

Seth Thomas cabinet clock?

I opened the back panel, quickly glanced at the movement and the trademark stamp appeared to be Ansonia. I had worked on an Ansonia Syria shelf clock in the past year and it looked quite similar but it was an odd looking movement for an Ansonia. Ansonia movements generally have an arched plate, this one had a hump. No matter, I bought it.

Ansonia Syria cabinet clock

While at home I was able to examine the clock more closely.

What did I buy?

I discovered that the movement is made by the Seth Thomas Clock Co. not by Ansonia. The movement was made for about 12 years and was available from 1890 to 1902. The style of the case is also from the same period.

An exhaustive search of Seth Thomas clocks on the internet using keywords such as, shelf, parlour (parlor), cabinet, carved oak and mantel produced nothing. I then navigated to a well-known Seth Thomas database site, poured through hundreds of listings and again, zilch.

I began to realize that the case might not have been made by Seth Thomas, after all.

However, I was determined to find the maker. I searched for clocks made by other companies, starting with E.N Welch, Ansonia (because it is similar in style to the Syria), Gilbert, Sessions and finally Waterbury. When I used the term “Waterbury cabinet clock” I found it on an auction site. So, now I have a case made by a different maker than the movement.

What is a marriage?

Among clock circles it is generally accepted that if a clock has significant parts from another source, particularly the movement and put into a period correct case from a different maker, it is considered a marriage. If it has parts sourced from a number of other clocks it is a Frankenstein or Frankenclock. While this clock is not quite a Frankenclock it is certainly a marriage.

Waterbury Wren case

I am actually disappointed that this clock is a marriage

The case is a Waterbury model called the “Wren”. I found three Wren models, two with paper dials and one with the identical dial pan as my clock. It may well be that this dial pan is original to the case.

The concave brass bezel and glass are certainly more recent. When I first looked at the clock I knew that the brass bezel and glass were incorrect but that did not stop me from buying the clock. The original bezel would have been a piecrust design with flat glass. This glass bezel is from a 1930s vintage clock.

The back access door is made of plywood, a recent addition and, of course, there is no label. The original panel would have been made of solid wood and screwed to the sides of the case with a circular tin access port. The label would have been located on the outside under the port door or underneath the base,

Does the movement run?

The movement is complete with pendulum bob and ST key. It was sold as a non-running clock, but will the clock run?

While the movement was still in its case I applied mainspring oil to the tight mainspring, allowing a few minutes for penetration. I then removed the verge so that the time train would run freely, using my finger as a brake on the escape wheel. It was sluggish at first but eventually the sticky time side mainspring made several soft clunking sounds as it ran down.

You can see the very tight time-side mainspring in the next photo. Grime and built-up dirty oil over the years will seize a mainspring.

Once the mainspring was partially let down I reattached the verge and the clock would stop after a minute or so. There was definitely power going to the escape wheel but something else was amiss. It would skip a tooth or two with every rotation which told me that the pallets were too far from the escape wheel. There is an adjustment screw on an arm which allows the pallets to be moved closer (or further) to the escape wheel. I eventually found the correct distance and the clock began to run normally. At the same time I opened the crutch loop wider to allow more impulse.

This is certainly no substitute for an overhaul but a good diagnostic tool.

Meanwhile, the strike side ran perfectly.

The movement is running and keeping good time but it needs a cleaning and several wear issues addressed.

Seth Thomas 8-day time and strike movement

Next steps?

I am actually disappointed it is a marriage. Buying a clock is always a risk and if I had paid many times more for this clock I would have asked for my money back.

I am not sure what I am going to do with it but I am inclined to service it and perhaps put it on the market. If I sold it I would certainly disclose the fact that it has a period correct replacement movement from another maker.

Nevertheless, it would make an attractive clock once the case is cleaned, the movement is properly serviced and has the correct glass and bezel.

And, if I like it enough I might keep it.

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