How does the balance wheel affect accuracy? What were stopworks used for? Where are the meantime screws?
Learn the basics of jeweling, configuration styles, railroad standards, watch mechanics, movement sizes, winding and setting, dial construction, types of adjustments, and more.
Watch this short video to see how the mainspring torque pushes through the gear train and the lever escapement to impel the balance wheel to oscillate. The design of the watch in this video is typical of nearly all American models during the railroad era, containing a mainspring, three-wheel gear train, anchor or lever escapement, and balance wheel assembly.
These are the primary components in most pocket watches, though the visual layout may change between models:
All watches from the railroad era used a balance wheel as a means of achieving accuracy, and when paired with the escapement, let down the mainspring at a controlled rate. The earliest balance wheels were solid metal, while later models had expansion cuts to adapt for temperature changes and carried many pairs of weights around the rim of the wheel that added mass. Its steady beat was controlled by an oscillating hairspring, and most brands had some kind of regulator for fine adjustments that slightly increased or reduced the working length of the hairspring to adjust the rate.
These paired screws were used to make bulk timing changes by turning them in or out slightly. They were usually found near the balance wheel arms and were made with a special interference thread to prevent them from turning without force. Any company that failed to install them on their watches invited a century of hacks to molest the other weights to make timing changes.
When a watch inevitably slowed from thickening oils and had no mean-time screws to make adjustments, the lazy choice was to simply grind off the balance weights to gain time. At some later point the watch was cleaned properly, which then ran too fast because of the missing weight, so washers had to be added to increase mass - all of which ruined the positional accuracy.
The hairspring is the balance wheel's rebound mechanism, oscillating in and out five times every second. The coils of a flat spring all lay on the same plane, anchored at either end. At the center is the collet, a brass split-ring that grips the balance staff, and at the tail is the stud, produced in many different styles.
Prussian watchmaker Abraham Breguet is credited for inventing the overcoil hairspring, which put the final turn of the hairspring above all the other coils. While a flat hairspring applies lateral friction to the balance staff when it oscillates, the overcoil minimizes this effect by moving a much smaller distance.
Any anchor or lever escapement requires a roller jewel, which is mounted in the roller table. On every cycle of the balance wheel this jewel gives an impulse to the pallet fork via the cup at the end of the pallet arm. A guide pin behind the cup prevented the pallet fork from drifting too early by meshing with a crescent-shaped cutout milled in the edge of the roller table.
Overbanking occurs when the roller jewel becomes misaligned with the pallet, which was possible with the single roller design. The double roller was developed to address this, using a smaller lower table with an indent to mesh with a horizontal guard pin. This allowed the pallet arm to swing only when the roller jewel was in the cup, virtually eliminating overbanking.
By far the most common.
Used in barrels with internal hooks.
Used inside slotted barrels.
A watch barrel contains the mainspring, and a going barrel has a cover that snaps on tightly, leaving a very confined space for the mainspring to uncoil. Newer alloy springs have sharp edges that will snag on any ridges or serial numbers stamped inside this type of barrel, making for an occasionally erratic letdown. This is by far the most common design, using a slotted or T-end spring.
A hanging barrel consists of a barrel and cover that never touch each other, rotating on a common arbor and giving the spring more room. Waltham used this design on several of their models. The mainspring is allowed to unspool at a much smoother rate, producing more consistent torque.
Hanging barrels have an internal hook to anchor the mainspring.
A motor barrel has a pair of internal jewels between the winding arbor and the barrel and its cover. This increases accuracy by letting the mainspring unspool without friction, and when used with a hanging barrel makes for the smoothest letdown.
External jewels on the plate are entirely for show and to inflate the count, and do not reduce friction or improve accuracy.
The stopworks, or Maltese Cross, originated in Switzerland in the 1700s as a means of limiting mainspring travel in watches. A single-tooth drive cam was mounted on the barrel arbor, which mated with a driven wheel that had several open spokes and a single closed one. After a given number of rotations the closed spoke would lock the drive cam and prevent the mainspring from turning.
The intent of stopworks was isochronism, the ability of a watch to run at the same rate despite any changes in its power source. The red line in this graph represents the drive torque of any mainspring, and the stopworks allowed the movement to run only in the middle two-thirds of its linear force, where its power was most consistent.
Most stopworks have been tossed by lazy hacks as unnecessary.
A fully-jeweled railroad pocket watch contains seventeen jewels - a total of seven for the balance assembly and a pair for each piece of the gear train for ten more. In 1891 the Hampden Watch Co introduced the first 23-jewel watch in America, and the jewel race was on. Factories added jewels anywhere they could put them, like the mainspring arbor and unnecessary caps on the pivots.
Learn what jewels were made from, what they were for, where they were used, how they were mounted, and how to determine jewel count just by looking at the watch.
Open face was by far the most common, with the winding stem at the 12:00 position, and was available in every size that American watch companies had to offer. This configuration eventually became one of the primary railroad criteria.
There are four styles for open-face cases: threaded covers, snap-on covers, internal swing-ring, and hinged clamshell.
Hunter (hunting) placed the stem at the 3:00 position, and was not railroad approved. The cases have a front lid to protect the dial and glass crystal, which opens by depressing the crown.
There is no such thing as a double hunter or a half hunter.
A case is either hunter or it's not, though demi-hunters have numerals on the front lid and a small crystal to view the hands.
Sidewinders are hunter movements in open-face cases. Seldom purchased this way historically, this arrangement means the original gold-filled hunting case has likely been melted down.
Most collectors believe this configuration to be incorrect.
Conversion dials allowed hunter movements to be used in an open-face case by moving the seconds bit to the 3:00 position, returning the winding stem to 12:00. These began showing up after WWI, were usually made of metal or enamel, and could be railroad acceptable.
Reversible cases had a center ring that rotated within the frame, displaying the movement in either hunting or open-face style. This does not convert the movement, since its winding pinion doesn't change positions. For example, an open-face movement used as a hunter profile will simply be aligned as a sidewinder.
These were also called a Muckle case, after inventor E A Muckle.
No single part on an American pocket watch was as visible as the dial, and they came in a fantastic array of colors, designs and fonts. See all the familiar variants in one place, learn what dials were made from, how they were mounted, discover who applied for patents, and don't forget the section on hand styles and colors at the bottom.
All American companies offered full plate designs, with the balance wheel being the only visual component of the gear train. The balance wheel was recessed on some models, but was always located above the upper plate.
A 3/4-plate design protected the balance wheel between the plates. Some models split the upper plate between the barrel (mainspring) bridge and the gear train bridge, while others had a single plate to cover both areas.
A bridge movement also stacked the balance wheel inside the gear train, with as many as four separate upper plate bridges. A "false" bridge model was actually a single piece with shallow milling cuts to mimic the real thing.
Pendant, or stem-set, was the most common, though the design required twice as many parts as a lever-set variant. The hands are set by popping up the crown, which did not meet railroad standards because the hands could accidentally be reset. The watch is wound by twisting the crown in a ratcheting motion.
Lever-set watches did meet railroad standards, as long as it was an open-face model. Setting the time meant removing the bezel and pulling out a lever, which could be in several different spots around the dial. The watch is still wound by twisting the crown.
Key-wind and key-set watches also didn't meet railroad requirements. The watch was wound with a small square key through the back and the hands were set by removing the bezel, although a few were able to also set the hands from the back.
Pin, or nail-set, was largely a Swiss innovation and was seldom used on American brands. It was a clumsy design, requiring the pin to be held in while turning the crown to set the hands.
Gilded plates were the most common prior to 1880, chemically transferring a thin layer of gold onto bronze plates.
Nickel-plated bronze was an ideal choice into which dazzling patterns could be milled or turned, called damaskeening.
Two-toning required the initial step of masking of areas of the plates with wax and then gilding to achieve this look.
This effect was similar to two-toning, except the patterns were milled before the plates were gilded.
American Waltham pioneered this look, with the patterns milled after sand or bead-blasting the plates.
US Watch of Waltham was the first factory to etch a pattern with acid on mirror-smooth plates.
American watches used the Lancashire gauge, which is based on the dial plate of a O-size watch measuring precisely a standard inch in diameter as a starting point, with each ascending size adding exactly 1/30th of an inch. The additional 5/30 inches was for the mounting shoulder up to a 16-size watch, when the diameter was increased to 6/30 inches. Different countries had their own system, adding to the confusion.
The verge dates to the 1200s and used a pair of steel paddles mounted 90 degrees apart on the balance staff to alternately lock and release the crown wheel. It was bulky and the mating surfaces wore quickly, although they could be made very small. Combining the verge with a fusee made small watches possible.
Verge fusees inevitably speed up over time because of the wear of the mating surfaces. The soft brass teeth of the crown wheel become worn out against the steel paddles on the balance staff, reducing the travel of the balance wheel. This decreases the amount of time between impulses, causing the watch to gain.
The fusee was a very simple yet effective method of equalizing drive torque as the mainspring unspooled and lost power. The design dates back to the 1400s, with the earliest versions using gut or wire. When the watch is fully wound, the chain is coiled entirely around the fusee cone, and the mainspring is applying the largest force with the smallest amount of leverage. As the mainspring unwinds, the chain begins to wrap around the mainspring barrel, and its weakening pull is applied to the expanding spiral radius toward the bottom of the fusee cone.
Accuracy was the most important aspect of any watch, so high-grade movements were adjusted to keep better time. These adjustments offset the effects of friction, gravity, temperature, and the fading torque in a spent mainspring by fine-tuning the balance, and getting a watch to run accurately took hours of work by a skilled watchmaker.
The word is Greek for same time and is the accuracy of a watch whether the mainspring is fully wound or almost spent. Barrel stopworks, counter-balanced pallet forks, and hairsprings with overcoils all helped to equalize mainspring torque in pocket watches.
Changes in temperature affected the hairspring and the oils in a watch, altering its accuracy. Factory adjustments took days, with the watches kept running in cold boxes near freezing and hot boxes at 90°F. Bi-metallic balance wheels with expansion cuts and the invention of alloys like Elinvar in hairsprings in the 1920s helped to offset this.
A watch can be oriented pendant up or down, pendant left or right, or dial up or down. There are nine total adjustments - the six positional ones, isochronism, plus one each for heat and cold. When a movement was marked with a given number of positions it meant certain orientations, although this was not universal, and it was assumed that isochronism and temperature adjustments were included. Some factories milled the word "Adjusted" on the plates with no explanation of what that meant, while other firms inscribed the total number of adjustments to which the watch was timed against.
The growing country moved nearly everything by rail in the 1880s, so an accurate timetable between freights became increasingly important. For decades the railroad companies had generally accepted any 18-size 15-jewel watch for service, but in 1891 the Kipton, Ohio crash killed several people because an engineer's watch had stopped, and the rules changed.
Webster C Ball, a successful jeweler and store owner, was given authority as Chief Time Inspector, overseeing thousands of miles of track. New standards were adopted, and by the turn of the century a Railroad Grade watch was American-made, open-face, lever-set, either 16 or 18-size, had a minimum of 17 jewels and was adjusted for temperature and positions. It had to be equipped with a steel escape wheel, a micro-regulator, and a bold Arabic dial. Railroad workers were required to submit their watches for regular inspection, and the most important criteria was that any watch had to be accurate to within 30 seconds a week.
The earliest American watches ran on a "coarse" gear train, designed for precisely 4.5 beats-per-second (BPS). Multiplying 4.5 BPS by 3,600 seconds in an hour returns 16,200 beats-per-hour, or BPH.
In later years the balance rate would rise to 18,000 BPH to increase accuracy. That figure translates to 432,000 beats per day, 3,024,000 per week, 12,960,000 per month, and 157,680,000 per year.
With the advent of the lever escapement in the 1700s, English watchmakers chose 14,400 BPH (4 BPS) as their train speed, which would be mimicked by the earliest of their American counterparts.