A Sessions clock is on the bench 5 years later – what needs to be done?

A mechanical clock is a machine and all machines require periodic maintenance. Five years might be considered a long time since the movement on a Sessions time and strike mantel clock was first worked on when 2-3 years is the norm between service intervals but let’s agree that it has not been an easy time these past two years and priorities have shifted.

I have not opened this clock up since 2016 and I wonder if any surprises await me. I worked on this clock in 2016, so, it is a judgment on my own workmanship.

Sessions Beveled #2

It was purchased locally from a person who knew absolutely nothing about clocks, making a few bucks on whatever he could get his hands on. He could not tell me one darn thing about it only that it was not working. The case was in rough shape and it was less than $40, so, I bought it.

Although I had worked on several clocks prior to this one, it was an important part of my journey in clock repair because I was now able to put my newly acquired Bergeon bushing machine to the test.

Bergeon Bushing Machine
Bergeon Bushing Machine purchased in 2016

Back then I installed 10 bushings, replaced the pendulum bob and suspension spring, oiled the movement, reinstalled it, and refreshed the case. Not the best timekeeper in the world but that is the nature of spring-driven American clocks of that era (the 1920s).

Disassembly and Inspection

I always approach the inspection and servicing of a clock that I have serviced in the past in much the same way I would service a clock that has just come into my collection. The steps are identical; inspect, restrain mainsprings, clean all parts, peg out bushing holes, polish pivots, address wear issues, assemble, oil and test. This clock is no different.

Backplate off and showing the helper springs

First, remove the hour and minute hands. Next, put the clock on its face and remove the 4 screws that hold the movement in place. Pull the movement out of the case, place the case aside, and let the mainsprings down into the mainspring retention clamps.

Mainsprings are removed

Never attempt to take apart a spring-driven movement without first restraining the mainsprings. This is a very important first step in clock repair and it is obvious for safety reasons.

Mainspring contained in a clamp
Mainspring contained in a retention clamp

During the servicing, as I usually do, I will check all pivots and bushings but most particularly the mainspring clicks which is a well-documented weakness in Sessions movements.

As I began taking the movement apart I noticed a badly kinked suspension spring which will have to be replaced. This usually occurs when a clock is moved without removing the pendulum bob. We have had some home renovations this past two years and the clock has been moved about the house. My fault, actually.

I generally take many photos during servicing but there is no requirement this time since I have kept the photos I took from 2016. However, if anything is noteworthy at this juncture, I will record it.

One item I did not own five years ago was a high-quality ultrasonic cleaning machine. The movement is dirtier than I expected and there is blackish oil around some (not all) of the pivots. I was probably a little overzealous with oiling and perhaps not as careful as I should have been polishing the pivots. It definitely requires a good cleaning and my American-made L&R Quantrex 140 with internal heater will be put to good use.

Ultrasonic cleaner by L&R
Ultrasonic cleaner by L&R

I have been working with so many German movements lately I can’t remember the last time I worked on an American one, let alone a Sessions clock. It has been months, so, here we go!

I pulled the plates apart and inspected the movement for wear. There is more blackened oil up the train (mentioned above) than I was expecting which tells me that if not addressed now it will lead to accelerated wear of the pivots and bushing holes and eventual stoppage of the clock. There is the tiniest bit of wear on the 4th wheel back-plate but not enough to justify replacing at this time.

The second wheels, front, and back, which were not attended to then, may now need attention. The good news is that all the replacement bushings from 2016 remain in very good condition.

It looks like at least one new bushing on the strike side wheel, not surprising since it bears the brunt of mainspring power. While there is some wear on the other three I can live with it but the fourth on the strike side back-plate is somewhat oval-shaped as you can see in this photo.

Worn pivot hole on the strike side

Though not as bad as others I’ve seen in American clocks that are well worn, there is enough play in this wheel to justify a new bushing.

The New bushing

The click and rivet design are a special problem on Sessions clocks, and I am happy to see that both clicks are in good condition after 5 years. It might be unfair to criticize parts that are nearly 100 years old. The photo shows what a worn click would look like.

Worn click on another Sessions movement

After the parts are cleaned in the ultrasonic and thoroughly dried, the bushing holes are pegged and the pivots polished. Now for the new bushing.

The pivot measured 1.62mm and I chose one with an inside diameter of 1.60mm. After broaching (cutting followed by a smoothing broach) it was a perfect fit.

Now for reassembly. The strike side levers with helper springs under tension can often be a challenge to stay in place during reassembly but the key is patience. Oiling and testing are next.

What did the movement look like after 5 1/2 years? The blackish oil was a little concerning but overall the movement is in great shape. It is certainly cleaner and shinier than before.

And it runs like a charm.


2 thoughts on “A Sessions clock is on the bench 5 years later – what needs to be done?

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