Watchmaking Technical FAQ: Gear Ratios, Magnetism, Tolerances & Heat Treatment Explained

Frequently Asked Questions About the Technical Principles Behind Watchmaking

Behind every mechanical watch lies a world of precision engineering — gear ratios calculated to fractions of a tooth, tolerances measured in thousandths of a millimetre, and heat treatment processes that transform raw steel into components that last decades. Here are the most commonly asked technical questions, answered with authority.

What is a gear transmission ratio in a watch?

In watchmaking, the transmission ratio is defined as the ratio of the driven shaft speed to the driving shaft speed. The formula is: Transmission Ratio = Driver Gear Teeth ÷ Driven Gear Teeth. In structural design, the watch’s fixed transmission ratios must always be maintained: 1 hour = 60 minutes, 1 minute = 60 seconds, and the hour hand completes one revolution every 12 or 24 hours.

What are the three types of gear transmission in a watch?

Watch gear trains use three types of transmission: speed-increasing transmission (ratio greater than 1), speed-reducing transmission (ratio less than 1), and constant-speed transmission (ratio equal to 1). Most watch gear trains use speed-reducing transmission to step down from the fast-spinning escape wheel to the slow-moving hour hand.

What is the difference between unidirectional and bidirectional transmission?

Unidirectional transmission means the driving and driven relationship between gears remains constant throughout operation. Bidirectional transmission means the driving and driven relationship reverses in different stages — for example, during timekeeping the seconds wheel drives the minute wheel, but during hand-setting the setting wheel drives the minute wheel which in turn drives the seconds wheel.

What electrical units are used in quartz watches?

Quartz watches use four key electrical units: voltage in Volts (V), resistance in Ohms (Ω), current in Amperes (A) — with watches typically operating in microamperes (μA) — and capacitance in Farads (F), with practical units being microfarads (μF) and picofarads (pF). The relationship is: 1F = 10⁶ μF; 1μF = 10⁶ pF.

How does magnetism affect a watch?

In a watch, the balance spring and other steel components can become magnetized if exposed to strong magnetic fields — causing the watch to run fast, slow, or stop entirely. Modern quartz watch rotors use artificial magnets made from samarium-cobalt alloy or neodymium-iron-boron, engineered for precise, stable magnetic properties.

What voltage should a watch battery have?

A quartz electronic watch operates normally at a battery load voltage of 1.55V. As voltage drops, frequency decreases and the watch runs slow. The open-circuit voltage shown by a standard multimeter is not the working voltage — always measure load voltage, which must not fall below 1.55V.

What is the basic principle of timekeeping?

Every timekeeping instrument requires an oscillation system with a constant, uninterrupted period. Time is calculated using: Time = Oscillation Period × Number of Oscillations. In a mechanical watch, the balance wheel and hairspring provide this oscillation; in a quartz watch, a quartz crystal resonator provides it.

What are the two main parts of any watch?

Every watch is composed of two major parts: the movement and the exterior components. Exterior components serve three functions: reading instantaneous time, aesthetics, and protecting the movement. The brand and exterior components account for a very large proportion of the total watch price.

What is the difference between clearance fit, interference fit, and transition fit?

Clearance fit (running fit): hole is larger than shaft, allowing free movement — used for rotating components. Interference fit (press fit): shaft is larger than hole, components locked together — used for fixed assemblies. Transition fit: tolerances overlap; any given pair may have either clearance or interference depending on actual dimensions.

What is quenching, annealing, and tempering in watchmaking?

Quenching: heat above critical temperature (~800°C), rapidly cool in water or oil — increases hardness. Annealing: heat above critical temperature, slowly cool — reduces hardness for machining and relieves internal stresses. Tempering: reheat quenched component below critical temperature, cool in air or oil — eliminates brittleness and brings component to specified hardness and toughness.

What watch best demonstrates these engineering principles in action?

A skeleton watch lets you observe the gear train, escapement, and balance wheel in real time. Our Men’s 42mm Skeleton Automatic Watch is the ultimate expression of this philosophy. Explore our full collection:

• Men’s 42mm Skeleton Automatic Watch — see the gear train in motion on your wrist.
• Men’s Full Diamond Octagonal Luxury Watch — precision engineering meets uncompromising luxury.
• Vintage Leather Apple Watch Band — handcrafted quality for the modern wrist.