A mechanical watch contains over 100 tiny parts, some no larger than a grain of sand. They mesh together with clearances measured in microns, transmitting power from the mainspring to the hands with almost no friction. For decades, Swiss and Japanese manufacturers dominated this micro-precision world. But today, China has emerged as a capable source for high-quality watch movement parts, watch case machining, and other horology components. From entry-level fashion watches to mid-range automatics, many brands now rely on precision CNC machined parts OEM suppliers in China. This guide explores the specialized world of watch component machining, covering movement gears, pinions, bridges, cases, crowns, and buckles—including materials, micro-tolerances, surface finishing, and practical advice for sourcing from Chinese manufacturers.
Machining parts for a watch is different from any other industry. The scale is tiny, the tolerances are extreme, and the aesthetic requirements are unforgiving.
Micro dimensions. A typical watch gear (wheel) might be 2-10mm in diameter with teeth only 0.1mm wide. A pivot for a gear train can be 0.2mm diameter. Standard CNC lathes and mills aren't designed for this; you need Swiss-type lathes with micro-tooling, often with spindle speeds of 15,000-30,000 RPM.
Sub-micron tolerances. The clearance between a gear pivot and its jewel bearing is about 0.005-0.010mm (5-10 microns). For high-end movements, tolerances of ±0.002mm are common. That's one-fifth the thickness of a human hair.
Surface finish is critical. Any roughness on a gear tooth or a pivot increases friction and reduces power efficiency. Pivots are often polished to Ra 0.05μm or better. Gear teeth need smooth flanks to avoid chatter.
Aesthetic perfection. Watch cases, crowns, and buckles are visible and touched daily. They must have mirror-polished or brushed finishes with no tool marks, scratches, or edge burrs.
Material variety. Watch parts use stainless steel (316L), brass, titanium, bronze, and even gold or platinum. Each machines differently.
Chinese CNC shops that excel in watch parts typically have specialized Swiss-type CNC lathes (Citizen, Star, Tsugami), micro-milling machines, CNC sliding head lathes, and skilled operators who understand watchmaking. Many are located in Guangdong province (Shenzhen, Dongguan, Guangzhou) and Zhejiang (Wenzhou, Yiwu), where the watch and jewelry industries are clustered.
The heart of a mechanical watch is the movement—a complex assembly of gears (wheels), pinions, bridges, and the escapement. Movement components are the most demanding to machine.
In horology, gears are called "wheels" (e.g., center wheel, third wheel, fourth wheel) and the small gears that drive them are "pinions." They are typically made from brass (C36000 free-cutting) or nickel-silver (a copper-nickel-zinc alloy). The teeth are very fine—often module 0.1 to 0.5 (metric gear module).
Machining a watch gear:
The blank is turned on a Swiss-type lathe, including the pivot (the small diameter shaft that runs in a jewel bearing). Pivot diameter tolerance: ±0.002mm. Surface finish: Ra 0.05μm (polished).
The teeth are cut using a gear hobbing machine with a very fine hob. Alternatively, for small batches, wire EDM can cut teeth, but it's slower.
After cutting, the gear may be deburred by tumbling with fine abrasive media, then chemically polished or electro-polished.
A pinion is similar but has a smaller diameter and longer shaft. It may be machined from hardened steel (e.g., 20MnCr5) for wear resistance, with teeth cut after heat treatment using hard hobbing or grinding.
Tolerances for watch gears:
Tooth profile: ±0.003mm
Runout of pitch circle to pivot: 0.005mm TIR
Pivot diameter: h5 or h6 (e.g., 0.8mm -0.004/-0.006)
Pivot roundness: 0.001mm
Chinese shops that specialize in watch movement parts will have CNC hobbing machines and possibly gear rolling or stamping for high-volume quartz watch gears. For mechanical watch gears, hobbing or wire EDM is typical.
A bridge (or mainplate) is the structural framework that holds the gears in place. It is typically a flat plate with precision-drilled holes for jewel bearings and screw threads. Bridges are often made from brass (nickel-plated) or German silver (a nickel-copper alloy).
Machining a bridge requires a high-precision CNC milling machine with a small end mill (0.5-1.0mm). The critical features are:
Hole positions for jewel bearings: true position ±0.005mm
Hole diameters for press-fit jewels: H6 or H7 (e.g., 1.5mm +0.006/+0.000)
Flatness of the bridge: 0.01mm over the part
Threaded holes (often M1.0 to M1.6): class 4H or 5H
After machining, brass bridges are often nickel-plated (electroless or electrolytic) to prevent tarnishing and improve appearance. Some high-end movements use rhodium plating for a bright white finish. Chinese shops can outsource plating; ask about their plating partner.
For skeletonized bridges (cut-out patterns to expose gears), wire EDM or micro-milling is used. This is more expensive and typically for luxury watches.
The watch case protects the movement and gives the watch its character. Watch case machining is done from 316L stainless steel (the standard), titanium, bronze, or even precious metals. Cases can be machined from solid bar (most common for mid-to-high volumes) or forged near-net shapes (for high volume).
A typical watch case starts as a round or square bar of 316L. On a CNC lathe, the basic shape is turned: the back (caseback recess), the front (dial opening), and the side profile (lugs). Then the case moves to a CNC mill (often 4-axis or 5-axis) to machine the lugs (drilling spring bar holes), crown tube threading, and any pusher holes. Finally, the case is polished or brushed.
Critical tolerances for a watch case:
Dial opening diameter: H7 or H8 (e.g., 28.5mm +0.021/+0.000)
Caseback thread (if screw-down): class 6H/6g, concentricity within 0.05mm
Spring bar hole positions: ±0.05mm (for strap fit)
Crown tube thread: M3.0 to M5.0, class 6H
Water resistance sealing surfaces (caseback groove, crystal seat): Ra 0.4μm max, no scratches
After machining, cases are polished (mirror finish) or brushed (satin finish). Many Chinese shops offer both. For stainless steel, mirror polishing is done with abrasive wheels and compounds, then final buffing. Brushed finishes are achieved with abrasive belts or Scotch-Brite wheels.
For titanium cases, machining is harder (gummy, requires sharp tools and high coolant pressure). Polishing titanium is also difficult; many titanium cases are bead-blasted or have a brushed finish. Chinese shops with titanium experience are less common; ask specifically.
Small parts like crowns and buckles are also precision-machined and often have decorative features.
The crown is used to wind the watch and set the time. It consists of a knurled or grooved outer part, a stem (threaded to screw into the case), and sometimes a logo. Crowns are typically machined from 316L stainless steel or brass (then chrome or gold plated).
Machining a crown: on a Swiss-type lathe, the shape is turned, the knurling is rolled or cut, and the internal thread is cut. The stem may have a square or flat for the winding mechanism. Tolerances: thread class 6g, stem diameter ±0.01mm, knurling consistency.
After machining, crowns are polished or brushed. Some have a logo engraved or laser-marked on the top face.
For chronograph watches, pushers are small buttons on the side of the case. They are machined similarly to crowns but shorter, with a spring-loaded mechanism. The internal bore for the spring and plunger must be smooth and round (Ra 0.4μm).
Watch buckles (tang buckle or deployant clasp) are machined from stainless steel or titanium. A deployant clasp has multiple hinged parts, each machined from sheet or bar stock, then assembled. The hinge pins and spring bars are small-diameter precision-machined parts. Tolerances on hinge pin diameter: h6, surface finish Ra 0.2μm.
Chinese shops that make watch buckles often have stamping and CNC machining combined. For high volumes, stamping is cheaper; for low-to-mid volumes, machining from bar is more flexible.
Here's a practical guide to materials in watchmaking:
316L stainless steel is the standard for cases, crowns, and buckles. It is corrosion-resistant, polishes well, and is hypoallergenic. It machines reasonably well but work-hardens. Good for turning and milling.
Brass (C36000) is used for movement bridges, gears, and some cases (often plated). It machines beautifully (free-cutting), but tarnishes and is softer than steel. Must be plated for corrosion protection.
German silver (CuNiZn alloy) is used for higher-end movement plates. It has a warm silver color and doesn't require plating, but it's harder to machine than brass.
Titanium (Grade 2 or 5) is used for lightweight cases and buckles. It's biocompatible and very corrosion-resistant. Difficult to machine (gummy, high tool wear). Requires rigid setup and sharp carbide tools.
Bronze (CuSn8) is used for vintage-style cases. It patinas over time. Machines similarly to brass but slightly harder.
Nickel-silver (often called "nickel silver" despite containing no silver) is used for gear trains in some movements. Good machinability.
Gold and platinum are used for luxury watches. Machining is expensive and requires careful scrap recovery. Most Chinese shops will not machine precious metals unless you supply the material and accept high scrap loss.
Finishing is what makes a watch look expensive. For watch parts, several finishes are common:
Mirror polish (Ra 0.02-0.05μm) on case sides, bezels, and buckles. Achieved by progressive abrasive wheels and buffing compounds. Chinese shops with dedicated polishing departments can achieve this.
Satin (brushed) finish (Ra 0.2-0.4μm) on case tops and bracelet links. Done with abrasive belts or Scotch-Brite wheels. The direction of brushing must be consistent.
Bead blasting (matte finish) for titanium cases or tool watches. Uses fine glass beads. Provides a uniform, non-reflective surface.
Perlage (circular graining) on movement bridges. Small overlapping circles created by a rotating abrasive stick. This is a decorative finish for visible movement parts.
Geneva stripes (Côtes de Genève) are machined or engraved patterns on bridges. Requires specialized equipment or CNC engraving.
Plating (nickel, rhodium, gold) on brass parts. Chinese shops can outsource plating; ask for thickness and adhesion specifications.
When specifying finishes, be precise. Example: "Case sides: mirror polish, free of scratches and pits. Case top: satin finish, direction parallel to the lugs, Ra 0.3μm max."
Watch components require meticulous inspection. Chinese suppliers serving this industry should have:
Toolmaker's microscopes (20-50x) for checking small features, threads, and burrs.
Optical comparators for measuring gear teeth profiles and small contours.
Vision measurement systems (fully automated) for high-volume inspection of hole positions and dimensions.
CMM (contact or non-contact) for bridges and cases.
Surface profilometers for Ra measurements on polished surfaces.
Thread gauges (GO/NOGO) for crown threads and caseback threads.
Air gauges for small pivot diameters (0.5-2mm) with micron accuracy.
First article inspection (FAI) is mandatory for any new part. For gears, request a gear measurement report showing tooth profile, pitch error, and runout. For pivots, request roundness and diameter measurements.
Here's a practical selection process:
Step 1: Look for watch or jewelry industry experience. Ask if they have produced watch cases, crowns, or movement parts. Request samples or references. A shop that says "we can do anything" but has no watch parts in their portfolio is a risk.
Step 2: Check their micro-machining capability. Do they have Swiss-type lathes (Citizen, Star, Tsugami) with live tooling? Minimum bar diameter capacity? Can they machine parts under 1mm diameter? Do they have micro-milling (0.2mm end mills)?
Step 3: Evaluate their finishing capabilities. Do they have in-house polishing, brushing, and bead blasting? Or do they outsource? For high-quality mirror polish, in-house is better.
Step 4: Assess their quality lab. Ask for photos of their microscopes, vision systems, and profilometers. A shop that relies only on calipers and eyes is not suitable for watch parts.
Step 5: Request a trial part. Order a small batch (10-50 pieces) of a relatively simple part like a crown or a caseback. Inspect dimensions, surface finish, and thread quality. If that goes well, move to more complex parts like a gear or a case.
Many Chinese watch part suppliers are located in Shenzhen (especially the Henggang and Buji districts), Dongguan, and Guangzhou. There is also a cluster in Wenzhou (Zhejiang) for buckles and bracelets.
Watch parts are generally higher cost per unit than standard CNC parts due to precision and finishing. Here are rough benchmarks for medium volumes (500-2000 pieces per year):
Watch crown (316L, machined, polished): $1.50-3.00 each
Watch case (316L, 40mm, from bar, polished): $8-20 each (depending on complexity)
Gear (brass, 8mm, hobbed): $2-5 each
Bridge (brass, nickel-plated): $3-8 each
Buckle (tang, 316L, polished): $1-2 each
Lead times: For new parts requiring custom tooling (form tools, fixtures, hobs), add 3-5 weeks. Production lead times: 4-6 weeks for first article, then 3-5 weeks for production. Polishing and plating add 1-2 weeks. Shipping: air freight 3-7 days, sea freight 30-45 days.
Minimum order quantities: For custom cases, MOQs of 100-500 pieces are typical. For crowns and buckles, MOQs of 500-2000 pieces. Some shops accept prototype quantities (10-50 pieces) at higher per-piece prices (2-4x).
Based on real sourcing experience, here are frequent issues with watch parts from China:
Poor pivot polish causing friction. The pivot looks shiny but has micro-grooves that increase friction. Prevention: specify Ra 0.05μm maximum and require a profilometer report. Also ask for a sample part to test in a movement.
Inconsistent gear tooth profile. The gear meshes noisily or binds. Prevention: require a gear measurement report (tooth profile, pitch error, runout). Specify quality class (e.g., DIN 5 or ISO 1328 grade 6).
Sharp edges on case lugs. The spring bar holes have burrs that damage straps. Prevention: specify "all edges broken 0.05-0.10mm, no burrs." Inspect with a loupe.
Thread galling on crown tubes. The crown threads seize on the tube. Prevention: specify a lubricant or anti-seize coating. Also ensure thread class is correct (6H/6g).
Plating peeling on brass bridges. The nickel plating flakes off after assembly. Prevention: specify adhesion test (cross-hatch tape test) and require a report. Also ensure the brass is properly cleaned before plating.
The watch industry is evolving slowly, but Chinese shops are adapting:
High-end mechanical movement production. Some Chinese manufacturers are now producing complete mechanical movements (e.g., Seagull). This requires even tighter tolerances and skilled assembly. The supply chain for movement parts is growing.
Custom watchmaking (microbrands). Many small brands are launching with low volumes (50-500 pieces). Chinese shops are becoming more flexible, offering lower MOQs and quicker turnarounds.
Material innovations. Ceramic cases and components (zirconia) are becoming popular. Ceramic machining requires diamond tooling and is specialized. A few Chinese shops offer it.
Additive manufacturing for prototypes. 3D printing in metal (laser sintering) is used for case prototypes before committing to CNC machining. Chinese shops are adding this capability.
Automated polishing. Robotic polishing cells are being introduced to reduce labor costs and improve consistency. This is still rare but growing.
Sourcing watch movement parts, watch case machining, and other horology components from China is increasingly viable. From entry-level fashion watches to mid-range automatics, Chinese CNC shops can deliver quality that meets global standards—provided you choose a specialist with micro-machining experience, proper inspection equipment, and finishing capabilities. The key is to start with a trial of a critical component, verify their tolerances and surface finishes, and build a relationship with a trusted supplier. With patience and due diligence, you can source precision watch parts that keep time perfectly.
Need help sourcing precision machined watch components from China? Send us your drawings and annual volume estimates. We work with a network of Chinese CNC shops that specialize in watch parts—from gears and bridges to cases, crowns, and buckles—with micro-turning, gear hobbing, polishing, and plating capabilities. Free DFM feedback and quoting available.
A: Yes, several Chinese manufacturers (e.g., Seagull, Hangzhou, Liaoning) produce complete mechanical movements. However, for custom movement parts, only specialized shops with micro-machining and gear hobbing can do it. Most Chinese CNC shops are not set up for complete movement assembly; they produce individual components for movement assemblers.
A: With Swiss-type lathes, many shops can machine pivots down to 0.3mm diameter. For 0.2mm and below, specialized micro-machining centers are needed, which are less common. Ask the shop about their minimum diameter capability.
A: A true mirror finish has Ra 0.02-0.05μm and is completely free of scratches, pits, or orange peel. This is difficult to achieve consistently. Many Chinese shops can produce a "bright polish" (Ra 0.1μm) that looks good but may not be perfect under magnification. Request a sample case to judge.
A: Yes, some can. Titanium requires slower speeds, sharper tools, and high-pressure coolant. Ask if they have specific titanium machining experience. Also, titanium is harder to polish; many titanium cases are bead-blasted or brushed rather than mirror-polished.
A: For a case machined from bar (no forging), MOQs of 100-500 pieces are common. For forged cases (lower per-unit cost), forging die costs $5,000-15,000, so MOQs of 1,000-3,000 pieces are needed to amortize the die. Some shops accept low-volume runs (10-50 pieces) at significantly higher per-case prices ($50-100 each).
A: Knurling can be done by rolling (using a knurling tool) or cutting (using a CNC lathe with a special tool). Rolling is faster but less precise; cutting gives cleaner, more consistent knurls. Specify "cut knurling" for high-quality crowns. Also specify the knurl pitch (e.g., 0.5mm) and pattern (e.g., straight or diamond).
A: Rhodium plating is a specialty. Few Chinese CNC shops do it in-house; they outsource to plating houses that serve the jewelry industry. Ask about their plating partner and request samples. Rhodium is expensive (the metal itself costs $400+ per ounce), so expect higher costs.
A: For a brass gear requiring hobbing, lead time is typically 4-5 weeks for first article (including hob manufacturing if a custom module), then 2-3 weeks for production. If the hob already exists, lead time is shorter. Wire EDM gears (no hob) can be faster but more expensive per part.
Ready to source precision watch components from China? Contact us with your drawings and specifications. We'll match you with qualified Chinese CNC shops that specialize in watchmaking—from micro gears and bridges to cases and crowns. Free quoting and DFM feedback available.
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