On My Workbench | Type 89 Movement by Seth Thomas and a Strike Side Issue

The Seth Thomas Type 89 movement is a robust and well-regarded mechanical clock movement widely used in many of Seth Thomas’ mantel and shelf clocks from the early 20th century to 1938.

The movement was introduced in 1900 and became one of Seth Thomas’ most popular and enduring movements.

There are several variants (89A, 89C, 89D, etc.), each tailored to specific clock models. The differences often involve small design adjustments like the escapement, strike train, or gearing. For example, some had solid back plates, some cut out, and some had a passing bell on the half-hour.

All Type 89 movements are time and strike and eight-day running and most use a strip pallet deadbeat escapement or according to Seth Thomas’s literature a “half deadbeat” escapement which is reliable and relatively easy to service. The most striking difference between the half-deadbeat and a recoil escapement is that the escape wheel teeth slant forward into the direction of rotation. Advantages: it was cheap to produce and still has fairly decent time-keeping ability. This video (no sound) shows the action of the escapement.

I consulted a chart (below) describing all the variations of the 89 and from what I can deduce this one is a type 89C movement.

Two Important strike-side Issues

The movement was in good condition overall. It was cleaned up and three new bushings were installed. The escape wheel bushings front and back were the most worn. The next was the fourth wheel front plate, adjacent to the escape wheel.

One minor hiccup when reassembling was dealing with a broken helper spring on the lifting lever. Shortening the spring by taking one coil off the arbour did not pose any running issues.

_{Taken directly from the case on the day of purchase}

However, once the cleaning and wear issues were addressed two other problems remained. The strike would not go into warning and the hammer did not move when the strike side was pushed to run.

It seems that whoever previously worked on it did not properly set up the strike side, likely neglecting to position the stop wheel correctly to ensure the strike mechanism would go into warning. Warning refers to a brief preparatory phase in the strike mechanism. This occurs just before the clock strikes. When the time approaches a strike point (such as the hour or half-hour), the movement enters the warning phase to prepare for the strike sequence. The warning phase is essential for ensuring the clock strikes consistently and on time. Improper setup of the warning phase can lead to the strike train failing to run.

While reassembling the movement, position the paddle lever in one of the indents on the cam while ensuring the paddle itself rests in a deep slot of the count wheel. The paddle should be straight into the deep slot without touching either side and pointed directly at the main wheel arbour.

The warning wheel can be adjusted after reassembly. Once all the wheels and levers are in their respective locations, carefully separate the plates slightly at the flywheel corner, ensuring no other components shift out of place. Then, when the pivot is out of its hole and the lantern pinion is disengaged from the adjacent gear, rotate the stop wheel until its pin meets the stop lever. If the levers are correctly positioned, the movement will enter the warning phase.

_{The stop wheel is at the upper right,} _{with the pin}

The second issue involved the hammer strike. A previous repairer had over-bent the strike rod, creating alignment problems. On the opposite side of the strike cam wheel are two striking pins, which the strike rod must reach to activate the hammer and sound the coiled gong. In this case, the rod had been positioned too close to the center, preventing it from contacting the strike pins. After some trial and error and careful bending of the strike rod, the movement is now properly aligned and able to sound the strike.

The final step is thorough testing. Placed on the test stand, the movement will be carefully monitored over the next several days to ensure everything functions smoothly and reliably.

A Special Note

I would also like to recognize Saint Valentine’s Day (February 14th) and I hope that everyone takes the time to cherish those around them, whether through a kind word, thoughtful gesture, or simply appreciating the moments that make life special. Happy Valentine’s Day!

February 14, 2025 2

Wrapping up the servicing of a Seth Thomas type 89 movement

Seth Thomas is a well-known American clock manufacturer with a long history, and they produced a variety of clock movements over the years. The Type 89 movement is one of the many clock movements produced by Seth Thomas between 1900 and 1938.

Seth Thomas mantel clock from the 1930s — _{Seth Thomas mantel or shelf clock}

The mantel clock in question features the Type 89 movement. Acquired in the summer of 2023, this clock boasts a simple and straightforward design.

In the first part of this two-part series, I discussed the disappointments I encountered with the clock’s case.

Seth Thomas type 89 movement showing dirt and rust — _{Seth Thomas type 89 movement, dirty and rusty}

The focus then shifted to the disassembly process and my examination of the widely-used Seth Thomas Type 89 clock movement.

My observations highlighted a replaced mainspring on the strike side, the necessity for bushing work, and indications of rust, all of which posed challenges that I committed to addressing in subsequent stages such as cleaning, bushing, oiling, and reassembly.

The focus of this blog post is the completion of servicing of this type 89 clock movement.

The front plate of a type 89 Seth Thomas movement — _{Front of the type 89 movement} _{before disassembly}

Cleaning of the mainsprings

There is always the temptation to do nothing with the mainsprings if they look acceptable. However, cleaning the mainsprings is an essential part of clock servicing. Uncoiling and wiping the dirt and grime from the mainsprings with a cloth is the preferred method, but cleaning them with an ultrasonic cleaner is also an option.

In Part I, I cleaned the mainsprings in my ultrasonic cleaner and provided a rationale for this decision. Before I go any further, I’d like to emphasize a crucial point regarding the cleaning of mainsprings in an ultrasonic cleaner. This practice is not recommended and should only be considered as a last resort.

While cleaning mainsprings in an ultrasonic cleaner has little impact on the surfaces or mechanism of the cleaner itself the oil removed from the mainsprings generates a black liquid that contaminates the cleaning solution, rendering it ineffective for future use.

_{Seth Thomas type 89 mainsprings, note the replacement spring on the right}

Clamps have been applied to secure the mainsprings after oiling, and they’ve been set aside. Now, we move on to the next step: the bushing phase.

The back plate is removed on a type 89 Seth Thomas movement — _{Backplate removed}

Bushing the movement

As the movement is fully disassembled this is the stage where bushing work can be done.
I commend individuals who choose to bush by hand, but personally, It is not for me.

Various systems exist for bushing, with KWM and Bergeon being the two most widely adopted. It’s worth noting that neither system is inherently superior to the other, as preferences tend to vary among enthusiasts. When referring to a “system,” it’s important to understand that the bushings from one system are not interchangeable with those from the other.

That said I use the Bergeon system.

Bergeon 6200 Bushing Machine — _{Bergeon Bushing Machine}

Before bushing, I identify all the locations requiring attention and mark them with a Sharpie. There is no permanent mark as rubbing alcohol will easily remove all traces of ink.

I have an excellent assortment of bushings and have all the required ones for this project.

An assortment of Bergeon bushings, assortment #5488 — _{An assortment of Bergeon bushings, #5488}

Using cutters each hole is drilled out and chamfered, that is, removing the sharp edges to allow the pushings to be pressed in smoothly. As I insert each new bushing I test the fit by assembling the wheels to check how freely they move. This allows me to make small adjustments in the event the pivot is too tight in the bushing hole.

Cutting into the bushing hole with Bergeon bushing machine — _{Cutting into a brass plate}

Based on my initial assessment, the bushings for both the front and back plates of the escape wheel were the most worn. The next new bushing is the fourth wheel front plate, the one adjacent to the escape wheel. After three bushings everything looks good and the wear further down the train does not look too bad. A fourth bushing for the fourth wheel should be enough.

A cutting broach is used to enlarge any holes that are a tight fit for a pivot followed by a smoothing broach. To prepare for the wheels to go back in place all bushing holes are cleaned with pegs/toothpicks.

Test fitting the time-side wheels during the bushing process, type 89 Seth Thomas movement — _{Test fitting the time-side wheels during the bushing process}

In the photo above, the plates and gears look shinier after a session with the ultrasonic cleaner. However, it’s important to note that the main goal in clock repair isn’t to make everything as shiny as possible. The focus is on reducing wear and tear. Some dirt and grime on the plates might not come off completely during the cleaning process in every case and it is not something the clock repairer should be overly concerned with.

Back to bushing. There is a little bit of play on the second and third wheels but it is tolerable so, I think I will stop at this point.

Punching a 3.5 mm Bergeon bushing into a clock plate — _{Punching a bushing into the plate}

Were I in the clock repair business I would bush everything on the time train, or the entire movement for that matter, but since I usually inspect movements in my collection every 2-3 years I can address any additional wear at that time.

On to the strike train. In the first article, I mentioned that there was not much wear on the strike side which might be attributable to that side not being wound as often. The only hole that must be addressed is the cam wheel bushing on the front plate. Why this bushing hole is worn much worse than the others is a bit of a mystery.

Okay, all the work is done for a total of five new Bergeon bushings. The holes have been pegged, and the movement is now ready to be reassembled.

The one hiccup encountered during the bushing process was the malfunction of my caliper tool. Fortunately, this isn’t a major problem, as all the Bergeon bushings are uniform at 3.5mm outside diameter, with inside diameters of either 1.4mm or 1.5mm so I knew what size to grab first.

Reassembly

When dealing with American 8-day time and strike movements, there are challenges in configuring the strike mechanism accurately. Occasionally, luck is on my side, and I manage to place the paddle in the deep slot, position the lever in the lowest part of the cam wheel, and align the warning wheel just right on the first attempt.

A useful tip. If the lever is in the lower part of the cam wheel and the paddle is not in the deep slot, simply move the toothed count wheel sideways so that it does not engage the pinon and reposition the wheel till the paddle finds the deep slot.

No luck setting up the strike this time! If the strike train does not lock correctly it will simply keep on running and you will know that soon enough.

The plates can be partially pried open without the risk of all the wheels and levers springing out. Repositioning the warning wheel involves moving the fly aside, carefully extracting the 4th wheel from its pivot hole, and rotating it a quarter turn or so to ensure the warning pin aligns with the stop lever.

_{Seth Thomas movement on the test stand}

A minor issue with the hammer lever surfaced as it was not aligning correctly with the strike pins on the cam wheel. No disassembly of the movement is required for this adjustment. Simply loosen the bottom two nuts by the mainsprings, and the strike hammer can be removed to straighten it. After having been bent multiple times over the years, straightening it out resolved the issue.

Next, the movement is oiled with Keystone clock pivot oil and mounted on a test stand. After a week it is running and striking as it should.

And lastly, my new caliper arrived just as I was concluding the servicing on this clock.

Addendum

To properly configure the strike side, pay attention to the positioning of the levers as pointed out by the arrows.

In the above photo, the lower arrow shows the paddle in the deep slot, and the upper arrow shows the drop lever in the indent of the cam.

The upper arrow shows the position of the stop pin on the stop wheel. The lower arrow shows the locking lever.

February 2, 2024

Seth Thomas type 89 movement servicing

I acquired this mantel clock during the summer of 2023. From a distance, it looked very good but upon closer inspection what I thought was a rosewood veneer finish was in fact, a thin wrapper, so a bit of a disappointment.

Seth Thomas mantel clock — _{The simple lines of this clock was the main attraction}

However, the focus of this blog post is not the clock’s case but the ubiquitous type 89 clock movement found within that made its way into thousands of Seth Thomas clocks.

Disassembly

The first step is to remove the hour and minute hands. Working from the back, four case screws release the movement from its case. Things will go along more smoothly if the coiled gong is removed as well.

Looking at the back plate, the suspension spring and rod must be removed first. Then comes the regulating adjustments screw and rod which consists of releasing 3 machine screws and then pulling out the spline gear which is operated through the clock face by the small end of a double-ended winding key. Once that hardware is removed it is on to the removal of the back plate.

A view from the back, Seth Thomas type 89 movement — _A _{view of the movement}

There are 4 nuts (plus the pendulum rod retainer screw) to be removed, however, it is advisable to unhook the helper spring at the top and the hammer spring at the bottom before lifting up the plate. This will prevent the wheels from being dislodged as the back plate is removed.

If the wheels spring out, reassembling the wheels becomes a challenging task of guesswork to determine their correct locations, especially for beginners.

Brass helper spring hooked around a post of a type 89 movement — _{Brass helper spring hooked around a post}

As each part is removed place them in a hobby tray or receptacle so that nothing will be lost or misplaced. No matter what the skill level, separating the time side gears from the strike side is always a good practice.

Findings

Upon lifting the back plate, my initial observation was the replacement of the mainspring on the strike side at some point in the clock’s life.

Whenever I encounter a replaced mainspring, my immediate focus shifts to inspecting potential damage to the main wheel teeth and the lantern pinions in the second and third wheels. This is because the force of a break occasionally causes secondary damage along the gear train. This is often referred to as collateral damage. Fortunately, the components up the train in this movement are undamaged.

Backplate removed on the type 89 movement — _{Backplate removed}

An initial inspection of wear indicates a need for five new bushings on the time side, while only one is necessary on the strike side. Further examination may reveal more once a more detailed assessment is conducted.

Interestingly, the strike side shows less wear, indicating that it was seldom wound. My assumption is that after the repair of the mainspring, the owner decided it wasn’t worth the risk of another mainspring break and chose not to wind it frequently or at all.

More concerning is evidence of rust on the movement posts, some pivots, and the lantern pinions. The clock was obviously stored in a humid location for a period.

Two mainsprings for the type 89 movement — _Mainsprings

All parts were cleaned in the ultrasonic cleaner and thoroughly dried.

Despite my best efforts, I could not separate the main wheels from the mainsprings. I opted to place both the wheel and mainspring in the ultrasonic cleaner. This is not a typical practice for me as it dirties the cleaning solution and limits resue, but I intend to dispose of the cleaning solution after this servicing.

From control for the L&R ultrasonic cleaner — _{Ultrasonic cleaner}

That’s all for now

Despite encountering disappointment in the clock’s case, the disassembly and findings of the ubiquitous Seth Thomas Type 89 clock movement revealed a replaced mainspring on the strike side, a need for bushing work, and evidence of rust, presenting challenges that will be addressed in the upcoming stages of cleaning, bushing work, oiling, and reassembly.

I will conclude here and save the remaining details of the servicing for a subsequent post.

January 30, 2024

A Vintage Seth Thomas Clock with a peculiar veneered case

The Seth Thomas Clock Company, renowned for its long history dating back to the early 19th century, produced a variety of clock movements over the years, and among them is the Type 89 movement found in this clock.

Despite the absence of a specific year stamp, the clock’s design and construction suggest a manufacturing date in the mid to late 1930s. Upon initial inspection, it was evident that the clock was not functioning, a common issue with old clocks that have not run in years.

_{From afar the wood finish is striking}

Typically, clock movements face challenges related to low power output caused by wear and tear over time. The gradual deterioration of clocks during years of operation is often attributed to factors such as dirt accumulation, inadequate lubrication, and the lack of proper adjustments.

Although dirt accumulation can persist in a movement, causing friction and wear, I decided to see if I could get the clock to run. The process involved removing the hour and minute hands, releasing four screws securing the movement to the front of the case, removing the strike block, and taking the movement out of its case.

An initial inspection revealed no visible issues with either the time or the strike side. Both mainsprings were found to be wound tight and seemingly ceased, likely due to the accumulation of glue-like dirt between the coils that will prevent the clock from running.

_{Seth Thomas time and strike 8-day movement}

To reduce tension on the mainsprings and provide the necessary energy for the clock to start running, an unwinding of the mainspring was performed using a let-down set. Oil was also applied to the pivots, as a temporary solution. Mixing new and old oil is never a good idea as a harmful abrasive paste is produced that could accelerate wear on the pivots and bushing holes. The plan, therefore, was not to run the clock for an extended period but merely to see if it could run.

While relaxing the mainsprings enabled the movement to run strongly, an issue persisted on the strike side, necessitating further investigation. Despite this, no major issues were anticipated, and the next steps will involve disassembly, thorough cleaning, any remediation, reassembly, and testing.

But first, let’s look at the case.

The case

This clock caught my eye at a thrift shop in Renfrew, Ontario, Canada, primarily due to its attractive appearance with what seemed to be rosewood veneer. Intrigued and encouraged by the reputable Seth Thomas trademark, I decided to make the purchase, especially given the appealing price.

However, upon closer inspection at home, I discovered that what I initially believed to be genuine rosewood was actually a thin layer of faux wood wrapping, and to my disappointment, some of it was peeling off in a couple of very visible areas, the worst by the bezel catch.

_{The worn and peeling section is adjacent to the bezel catch}

There might be speculation about whether the movement was reinstalled in a newer case, but my inclination is that this is how it originally left the factory. What the Seth Thomas company might have considered new and improved and would likely fool most consumers was but a cheap imitation.

It is clearly a cost-cutting measure rather than a later modification. Many clock companies faced financial difficulties during the Depression Years of the 1930s, leading them to seek cost-saving measures but honestly, this discovery is rather disheartening.

Nevertheless, the clock holds value because of the movement, which still has many years left. Join me later as we dismantle the clock movement and address any required repairs.

December 15, 2023

The ubiquitous type 89 movement by Seth Thomas

The Seth Thomas Clock Company is a well-known American clock manufacturer with a long history dating back to the early 19th century. The Type 89 movement is one of the many clock movements produced by Seth Thomas over the years. This type was made between 1900 and 1938.

This is a first look at the movement of a Seth Thomas time and strike mantel clock with a type 89 movement. Since there is no year stamp on the clock movement I am surmising that this clock was manufactured in the mid to late 1930s judging from its design and construction.

Discovered at a thrift shop in Renfrew, Ontario, the clock was not functioning initially.

Generally speaking, a clock movement faces issues with low power output caused by friction resulting from wear over time. The primary issue with aging clocks is their gradual deterioration due to extended periods of operation. Common culprits are dirt accumulation, insufficient lubrication, and lack of proper adjustments, although these are unlikely to be the reasons for the malfunction.

Interestingly, a dirty movement often continues to function even without lubrication if it’s in decent condition. There is no doubt that this movement requires bushing work to address accelerated wear, yet regrettably, I do not currently have access to the necessary bushing tools for the task as I am on holiday.

Despite the accumulation of grime, and potential wear-related concerns, I opted to put the movement into action, primarily with the goal of uncovering underlying issues. Doing this required removing the hour and minute hands, releasing 4 screws holding the movement to the front of the case, removing the strike block, and taking the movement out of its case.

Once on the work bench an initial inspection of the movement did not reveal any obvious issues with either the time or the strike side, so, it was safe to proceed further. When found both mainsprings on this time and strike movement were wound tight and appeared ceased likely as a result of the build-up of glue-like dirt between the coils of the mainsprings.

I have found that in some cases gently unwinding the coils of mainsprings with a let-down set can often relieve enough tension to provide a clock with the necessary energy to start running but there was one more step in the process.

_{A letdown set is required in order to release the mainsprings}

Although there was a noticeable amount of dirt around the pivots, I applied oil to each one. However, it’s important to be cautious about mixing new and old oil, as their interaction can result in the formation of a harmful abrasive paste, which can speed up wear on both the pivots and the bushing holes.

Thus, while oiling a dirty movement is a temporary solution, it’s not a replacement for proper disassembly, thorough cleaning, and addressing wear issues.

As a result of releasing the mainspring, oiling the pivots, and putting the movement in beat, it now runs strongly. However, there is something amiss with the strike side and further investigation is required. Despite this, I am not anticipating major issues with this movement.

The next step is disassembly, cleaning, reassembly, and testing. Should it require bushing work, that step will have to wait a while longer.

I have every confidence that this movement will run very well once serviced.

August 25, 2023

Two Important strike-side Issues

A Special Note

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