Pocket Watches Advanced

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How does the balance wheel affect accuracy? Where are stopworks used? What is a meantime screw? What does railroad-grade mean?

Learn the basics of jeweling, configuration styles, movement sizes, winding and setting, dial construction, types of adjustments, watch mechanics, railroad standards, and more. There isn't nearly enough room on this page to cover everything, but it'll get you started.

All watches from the railroad era used a balance wheel as a means of achieving accuracy.  The earliest wheels were solid metal, while later models were bi-metallic with expansion cuts to adapt for changes in temperature and carried weights that added mass.

Its steady rate was controlled by an oscillating hairspring, and nearly all models had some kind of regulator for fine adjustments.

Most models used at least one pair of these special screws to easily make bulk timing changes.  They are usually found near the ends of the balance wheels 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 (Elgin) 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 way too fast because of the missing weight, so washers had to be installed to add mass - all of which thoroughly ruined the positional accuracy. 

Any watch using an 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 located at the end of the pallet arm. A vertical 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 cup, 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, eliminating overbanking.

The stopworks, or Maltese Cross, originated in Geneva, Switzerland in the 1700s as a means of limiting mainspring travel in watches.

The device was located on the mainspring barrel, and consisted of a single-tooth drive wheel mounted on the arbor that mated with a driven wheel with a single closed spoke and several open ones. After a specific number of rotations the closed spoke would lock out the drive wheel and prevent further turning of the mainspring. 

The intent of stopworks was isochronism, the ability of a timepiece to run at the same rate regardless of changes in its power source. The red line in the graph represents drive torque in a mainspring, and the paired stopworks allowed the watch to run only in the middle two-thirds of its linear force, shown in green.

Most stopworks have been tossed by lazy hacks as unnecessary.

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 a requirement as one of the primary railroad criteria.

There are four primary 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 had a front lid to protect the dial and crystal, which opened by depressing the crown, along with several hinges, a dust cover, and springs for the front cover and the latch.

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.

Simply put, 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, and could be railroad acceptable.

Reversible cases had a center ring that rotated within the frame, allowing the movement to be displayed as either a hunter or an open-face style. However, this does not convert the movement, since the winding pinion doesn't change positions. For example, an open-face movement with the winding stem at 12:00 used as a hunter profile will simply be aligned as a sidewinder.

These were also called a "Muckle" case, after inventor E A Muckle. 

Pendant (or stem-set) was the most common, even 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 the 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 locations around the rim. The watch still gets 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) setting was largely a Swiss innovation and was seldom used on American brands. It was a clumsy arrangement, requiring the pin to be held in while turning the crown to set the hands.

 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 the first pocket watches possible.

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.

Verge fusees inevitably speed up over time because of the design and the wear of the mating surfaces. The 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 run faster.