How a Watch Is Made: The Complete Manufacturing Process

Everyone knows that a watch is an extraordinarily precise instrument, demanding the highest levels of technical skill. Yet the full process by which a watch is produced and assembled is something few people truly understand. For those in sales, marketing, and watchmaking, a thorough knowledge of the manufacturing process is invaluable. This is the complete story of how a mechanical watch is made.

A standard mechanical watch is composed of more than 100 components of varying shapes and sizes. An automatic calendar watch contains approximately 200 parts. Watches with complications such as a tourbillon, perpetual calendar, minute repeater, or other complex mechanisms may contain far more. The world’s most complex mechanical watches can have over 1,000 individual components.

With the exception of the mainspring, hairspring, jewel bearings, and shock absorbers — which are supplied by specialist component manufacturers — all remaining parts are manufactured in-house by the watch factory. This is what defines a true manufacture.

The production of a standard hand-wound mechanical watch involves more than 1,000 individual manufacturing steps, requiring close to 1,000 different tools and fixtures, carried out on nearly 1,000 high-precision machines and instruments. Watch components are extremely small, with exceptionally tight tolerances for machining precision and surface finish.

I. Raw Materials

The principal materials include leaded silver-bright steel bar stock (for gear shafts and screws), leaded brass bar stock (for barrel wheels, barrel covers, hour wheels), nickel-silver bar stock (for ratchet wheels), free-cutting steel strip (for lever plates), high-quality carbon tool steel strip (for steel wheels), leaded brass plate and strip (for bridges and plates), brass strip (for dials and hands), stainless steel (for cases and casebacks), and organic glass and acrylic rubber (for crystals and gaskets). All raw materials must pass incoming inspection before entering production.

II. Automatic Lathe Machining (Screw Machine Shop)

Approximately 40 types of watch components require machining on automatic lathes. Simple components are completed directly on the automatic lathe, followed by heat treatment or electroplating. Most components — including gear shafts, fork shafts, pallet levers, and balance staffs — are rough-turned and then undergo many additional machining operations. The process simultaneously performs turning, facing, parting, chamfering, drilling, reaming, tapping, thread cutting, and milling of slots — all in a single fully automated cycle. Dimensional accuracy is within 0.01 mm; surface roughness reaches Ra 0.4–0.8 μm.

III. Gear Cutting (Machine Shop)

Gear teeth are hobbed on a gear-cutting machine, followed by quenching, tempering, and lapping to achieve a tooth surface roughness of Ra 0.05–0.1 μm. Tooth form is verified on a 100× projector. Carbide grinding wheels grind shaft journals and end faces to Ra 0.05–0.1 μm. The copper wheel plate process involves die blanking, gear hobbing, gold plating, and press-fitting with the gear shaft. Steel gear wheels must be quenched and tempered.

IV. Setting Lever System Components (Lever Shop)

The lever plate is milled with 15 special tooth forms, quenched, tempered, and lapped. Every component is inspected on a 50× projector; tooth form error must not exceed 0.01 mm. The lever fork is milled, nickel-cobalt alloy plated, and fitted with entry and exit pallet stones locked with molten shellac. The balance staff is ground to a diameter of φ0.085 mm (tolerance −0.005 mm) and surface roughness of Ra 0.025–0.05 μm, inspected under a 40× microscope, then fitted to the balance wheel. The lever plate, lever fork, and balance staff are the heart of the watch — their quality directly determines timekeeping accuracy.

V. Plate and Bridge Machining (Plate Shop)

Plates and bridges involve more than 200 machining operations. The main plate has 34 through-holes and 3 cross-holes; the smallest hole is only 0.5 mm in diameter. Diameter tolerance of transmission holes is ±0.005 mm; positional tolerance of hole centers is ±0.008 mm; concentricity tolerance is ±(0.007–0.008) mm. After machining, locating pins, pin sleeves, and synthetic ruby jewel bearings are press-fitted. The surface is electroplated with nickel-cobalt alloy. Plates undergo multiple time-effect treatments to eliminate internal stresses and prevent deformation in service.

VI. Case and Dial Components (Dial and Case Shop)

The watch case is hot-pressed from stainless steel, then turned, sandblasted, and polished. The caseback is cold-pressed, turned, sandblasted, polished, and stamped with markings. Today, most watch crystals are made from synthetic sapphire crystal. The dial is brass strip, stamped on a 300-tonne press, then silver plated, brushed, diamond-tool engraved, gold plated, printed, and coated with a thin anti-glare film to protect against discolouration.

VII. Thermal and Chemical Processing (Heat Treatment Shop)

Steel components must be quenched and tempered to improve mechanical properties and hardness. The balance staff — as fine as a human hair — oscillates more than 20,000 times per hour and must function reliably for one to two decades. Watch component heat treatment uses protective atmosphere bright quenching and tempering; surfaces must not decarburize or oxidize. Most watch components are electroplated: movement components receive nickel-cobalt alloy plating; dials receive silver and gold plating; some components receive rhodium or rose gold plating.

VIII. Watch Assembly (Assembly Shop)

Watch assembly is performed in clean, air-conditioned rooms at 18–25°C with relative humidity not exceeding 70%. All components must be thoroughly cleaned before assembly. Dust and corrosion are the “hidden enemy” of watches — invisible contamination frequently causes watches to stop or run erratically. Many components must not be touched by bare hands.

The balance wheel is statically balanced with an imbalance moment of less than 7 micrograms·cm. The balance wheel and hairspring are graded and matched by grade number. The mainspring is loaded into the barrel wheel with dedicated grease; the barrel arbor must have 0.01–0.04 mm of axial clearance. After fitting the crown-setting mechanism, the movement enters the assembly line.

Setting lever mechanism assembly is critical: entry and exit pallet stone lock values must be 0.09–0.11 mm; the safety clearance between the fork pin and safety disc must be 0.05–0.06 mm; the lever fork shaft axial clearance must be 0.01–0.04 mm. After fitting the balance wheel and hairspring, the balance staff axial clearance must be 0.02–0.04 mm. The clearance between the fast-slow regulator clamps must be 0.045–0.065 mm. If the hairspring rubs against the clamp, the watch’s isochronism is compromised — this is not acceptable.

IX. Quality Inspection (Inspection Department and Finished Product Inspection Station)

A watch is a precision timekeeping instrument; inspection is critically important throughout production. A system of self-inspection, mutual inspection, and specialist inspection is strictly observed at every stage. All precision gauges are calibrated by the metrology laboratory.

The finished product inspection station conducts a comprehensive 13-day inspection of every watch: 12-day timekeeping rate inspection in 6 positions, continuous running inspection, amplitude inspection, and appearance inspection. Only watches that pass all inspections are released for shipment.

Note: Excerpted from Horology Reference Compilation, with editorial revisions.

Precision Born from Process

Every watch carries within it thousands of hours of human skill and a quality standard measured in microns. At Aorawa Time, we honour this tradition in every piece we offer:

• Men’s 42mm Skeleton Automatic Watch — witness the movement of time through an open dial.
• Men’s Full Diamond Octagonal Luxury Watch — precision engineering meets uncompromising luxury.
• Vintage Leather Apple Watch Band — handcrafted quality for the modern wrist.