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Many 30 hour spring driven American antique shelf clock are operating with mainsprings that are WAY too strong! The original springs are often stronger than necessary, but clock repairers have replaced then with springs that are even stronger!

A nice little (17-3/8 inches tall) Seth Thomas I have now (in for adjustment and to have the minute hand properly fitted) has a replacement time mainspring that is feels very strong when it is being wound, at least twice the force that is needed! The clock ticks very loudly! I am going to recommend to the customer that the movement be overhauled and the spring replaced. Or, if he doesn’t want to have that done, I will explain and write on the bill that the mainspring is way too strong, is causing excessive wear, and the clock should not be operated very often.

Job no. 4525

Thanks to Bryan Smith on the Clocksmiths group for sharing the following links to classic out of print clock and watch books that Google has digitized. They may be viewed for free!

On the Construction and Theory of Dead Escapement Clocks, B. L. Vuliamy,

New and Complete Clock and Watchmakers’ Manaul, Mary L. Booth, 1863

Treatise on Clock and Watch Making, Thomas Reid, 1826

Treatise on Clock and Watch Making, Thomas Reid, 1832

Lessons in Horology, Jules and Hermann Grossman, translation, 1905

Horlogical Journal, 1860

A Portion of the Papers Relating to the Great Clock for the New Palace at Westminster, 1848

The Tower Clock Designed and Made for the University of Chicago, 1903

The Clock Jobbers Handybook, A Practical Manual on Cleaning, Repairing and Adjusting, Paul Hasluck, 1889

A Treatise on the Teeth of Wheels, M. Camus, Trans by Hawkins, 1868

A Rudimentary Treatise on Clock and Watch Making with a Chapter on Church Clocks and an Account of the Proceedings Respecting the Great Westminster Clock, Edmund Beckett Dennison, 1850

Watch and Clock Making, David Glascow, 1885

Former Clock and Watchmakers and Their Work, F. J. Britten, 1894

The Watch & Clockmakers Handbook, Dictionary and Guide, F. J. Britten, 1896

Clock and Watch Work (by E. Beckett), from the 8th Edition of the Encyclopedia Britannica,

Time Telling Through the Ages, Brearly, 1919

A Treatise on Watch-Work, Past and Present, Rev. H. L. Nelthropp, 1873

Five Hundred and Seven Mechanical Movements, Henry T. Brown, 1881

This is a good looking Seth Thomas oak kitchen clock.

Date stamp on the back reads 7981 which translates to the year 1897.

Movement Before Repair

Front of movement showing two crudely soldered on “Rathbun” bushings (on pivots T3F and T5F). This type of work is done by someone who does not like to take the movement apart.

The “Rathbun” bushing on the back of the movement (on pivot T4B).

Movement After Repair

The movement after repair. The previous repairer had gouged the brass very deeply. I didn’t want to remove too much material, so the gouges are still visible.

Movement Assembly

Showing the relationship of the lift/warning lever to the j shaped turnback lever. The turnback lever is riveted to the back plate. Its function is to hold the warning lever in the correct resting position so that the minute hand may be turned back past the numeral “12″ without damaging the movement.

Partially assembled movement showing the gears and levers.

This great looking clock has the original time and strike mainsprings, and only a small amount of mainwheel tooth wear (about 5%).

T: 3/4 wide x .0172 inch thick

S: 3/4 wide x .0172 inch thick

Label on back of case

The 8 day time and strike movement

Back of movement

My job no. 4501

American antique one day spring driven clocks often have mainsprings much stronger than necessary. This can cause severe wear to the mainwheel teeth. Shown here is a Waterbury walnut case kitchen or shelf clock, ca. 1880. The movement has a patent date of September 22, 1874.

The movement has the original strike mainspring of 1/4 inch wide by 0.019 inches thick. Yes, this spring is very thick, but it is not very “springy” and does not provide much force, so there is NO wear on the mainwheel teeth.

The time spring was a replacement of 1/4 inch wide by 0.0157 inch thick. There is about 30% wear to the time mainwheel teeth. I replaced it with a mainspring 5/16 inch wide by .0125 inch thick by 45 inches long (actual specifications: 8 mm x 0.33 mm x 1150 mm). This spring provides plenty of power, enough for the movement to run about 48 hours on a winding. This spring is part no. PM-CS510 from The PM Company. They have a great online and printed catalog, including hard to find parts for Swiss travel clocks.

My job 4365

The movement is designed to accommodate 5/16 inch wide mainsprings.

As received: the time mainspring was 3/4 inch wide by 0.0175 inch thick, and the strike mainspring was 0.0165 inch thick. There was very bad T4F pivot hole wear. The strike train had virtually no wear.

Showing front time pivot holes 3, 4, and 5 before bushing. Note excessive wear on #4

After the overhaul, (I did no bushings on the strike side), the pendulum motion was excessive, and the striking sounded sluggish. I swapped the time and strike mainsprings, and then the pendulum motion was excellent (could still have been less) and the strike sounded fine. Here are the final values of the mainspring sizes (remember that these are ORIGINAL OLD mainsprings, if they were being replaced, thinner spring should be used):

Time Spring: Original old 3/4 x 0.0165 inch

Strike Spring: Original old 3/4 x 0.0175 inch

The bottom of the clock showing date code “6091L” which means December 1906.

My job no. 4487

I just repaired an Ingraham oak shelf clock, with a date of 6 14 (June 1914) on the movement.

A previous repairer had installed a time mainspring that was way too strong (.018 inch thick), which had caused about 50% tooth wear on the time mainwheel. After the overhaul, I installed a Merritt’s P1496 mainspring 3/4 inch wide, 0.0155 inch thick, and 96 inches long. This gives a moderate amount of overswing to the pendulum, only time will tell if the power is sufficient to reliably run the clock for a long period. If not, I will install a spring about 0.0165 inch thick.

The strike train has its original mainspring of 3/4 x 0.0172 inches.

My job 4469.

Follow up: On 2/28/08, the clock came back because it would sometimes stop at three minutes before the hour. I did two things to correct this:

1. Smoothed the tip of the strike locking lever.
2. Replaced the time mainspring with one of the new Merritt’s 3/4 x 0.0165 x 96 inch spring.

I just overhauled a Schatz 8 day cuckoo clock. The movement is model 50 (has a 50 in the circle on the back plate). The customer has the top piece, so I could not include in in the photo. The nicely made movement has some surprises!

• The movement plates are very classy with the design of a bird worked into them,
• Separate controls for door and bird - bird goes in and out with each cuckoo while the door stays open,
• The cuckoo and time train are on the opposite sides of the movement, compared to the majority of cuckoo movements,
• Very large teeth on the time first and second wheels.

The weights are 2 lb, 12 oz. and 2 lb, 14 oz.

My job no. 4492. This clock had probably seen years of use, as many of the pivots needed to have wear removed and be polished. I installed 14 bushings.

The circle on the back plate says:

JAHRESUHRENFABRIK
50
GERMANY

The rectangle says:

NO (0) JEWELS
UNADJUSTED

Jahresunherfabrik means “Year Clock Company”. This was the company’s name for many years, as they started out as a manufacturer of 400 day or “Anniversary” clocks. In the early 1950’s they became known as Aug. Schatz and Sohne.

The photo above was made before the movement cleaning, as the dirt in the engraving makes the lettering show up better!