Why Your Watch Case Needs ±0.005 mm Tolerance, Not ±0.05 mm CNC machined watch case parts brass are the structural heart of your timepiece. We machine brass cases and case components (lugs, bezels, cr
CNC machined watch case parts brass are the structural heart of your timepiece. We machine brass cases and case components (lugs, bezels, crowns, casebacks, tube inserts) to a tolerance of ±0.005 mm and a runout of 0.01 mm. That means your case fits your movement, gasket, and crystal without shims, without rework, and without field failures. You get a consistent, repeatable case that snaps together smoothly the first time, every time. Our standard lead time is 7 days for prototypes, 15 days for production runs.
We machine C36000 free-cutting brass as the default for watch case parts. It gives you machinability at 100% (vs. 40% for stainless steel), which means faster cycle times and lower unit cost. For higher corrosion resistance in humid environments, we use C38500 (architectural bronze), which resists tarnishing better than C36000. If you need a lighter case for a dress watch, we also machine 6061-T6 aluminum with a hard anodized finish — but the brass parts remain our core competency. We stock round bar from 8 mm to 80 mm diameter, so your case diameter can range from 28 mm to 52 mm without custom material orders.
Brass in the as-drawn condition measures 65 HRB (Rockwell B). That is adequate for most watch cases. But if you need a caseback that resists deformation from repeated opening, we can specify heat-treated brass to 75 HRB. Conversely, for deep engraving or intricate bezel work, we anneal to 40 HRB so the cutter does not push the material. We do not do full hardening (that is for steel cases), but we control hardness to your drawing. We document the hardness reading for every batch on the inspection report.
Watch cases demand a mirror finish on the visible surfaces. We achieve Ra 0.2 µm directly from the CNC machine using polished carbide inserts and high-pressure coolant (70 bar). That eliminates the need for secondary barrel polishing on flat bezels. For brushed finishes, we use a multi-axis pass with a 400-grit abrasive belt, giving you a uniform hairline texture at Ra 0.4 µm. Threads on the caseback are cut to a 6H tolerance, so your caseback screws on smoothly without cross-threading. Our toolpath strategy controls chip flow so brass chips do not scratch the finished surfaces — a common issue with cheap machining.
The critical dimension on any watch case is the gasket groove and the crystal seat. If the runout exceeds 0.01 mm, your gasket compresses unevenly, and water ingress follows. We machine the crystal seat and the caseback groove in the same clamping operation on a 5-axis CNC mill. That guarantees concentricity between the two features to within 0.01 mm total indicated runout (TIR). We also deburr every internal edge with a robotic brush, so the gasket does not get cut during assembly. This is the difference between a 50-meter water resistance rating and a 100-meter rating.
Every batch of CNC machined watch case parts brass ships with a full inspection report. We measure critical dimensions on a Zeiss CMM (coordinate measuring machine) with a resolution of 0.0001 mm. We check: outer diameter, inner diameter, crystal seat depth, gasket groove width, thread pitch, and surface finish. Runout is verified on a Talyrond roundness machine. Hardness is measured on a Rockwell tester. You get the CMM report as a PDF with your shipment. If you need a PPAP (Production Part Approval Process) document, we provide that within 3 days of sample approval.
| Parameter | Value |
|---|---|
| Materials | C36000 brass, C38500 bronze, 6061-T6 aluminum |
| Case diameter range | 28 mm – 52 mm |
| Hardness (as-machined) | 65 HRB (typical), up to 75 HRB (heat treated) |
| Machining tolerance | ±0.005 mm (critical features), ±0.01 mm (standard) |
| Concentricity / runout | 0.01 mm TIR (crystal seat to caseback groove) |
| Surface finish (visible) | Ra 0.2 µm (mirror), Ra 0.4 µm (brushed) |
| Thread tolerance | 6H (caseback thread) |
| Lead time (prototype) | 7 days |
| Lead time (production) | 15 days for 1,000 pcs |
| MOQ | No MOQ – start with 1 piece |
You do not need to order 500 pieces to test a design. We machine a single prototype for you within 7 days. That prototype is machined on the same CNC machine, with the same tooling, as your production run. So what you approve is exactly what you get. Once you approve the sample, we ramp up to production in 15 days. For a batch of 1,000 cases, we deliver in 15 days. For 5,000, add 5 more days. No MOQ means you can also use us for replacement parts or small-batch luxury editions.
Our factory in Dongguan runs 24/7 with 20 CNC machining centers dedicated to watch parts. We keep C36000 brass bar stock in-house for the 10 most common case diameters (28, 32, 34, 36, 38, 40, 42, 44, 46, 48 mm). That eliminates material procurement lead time. We use a standardized tooling library (carbide end mills, drills, and threading tools from Mitsubishi and Sandvik) so we do not wait for special tool orders. Our programmers use a lookup table of proven toolpaths for watch cases, so the first run is already optimized. That is why we can quote you a firm delivery date within 12 hours of receiving your drawing. For tooling and tolerance details, check our CNC cutting tool selection guide and CNC machining tolerances guide.
A typical 40 mm brass case weighs 32 grams. At current brass prices, the material cost is approximately $0.85 per case. Stainless steel (316L) costs $1.20 per case but takes 3x longer to machine. The total machining cost for a brass case (including 5-axis milling, threading, and polishing) runs $4.50 to $7.00 per piece at 1,000 quantity. The same case in 316L runs $9.00 to $14.00. That is a 50% cost saving. For a watch retailing at $200, that saving is significant. Plus, brass is easier to plate (gold, rhodium, or nickel) because it accepts plating without a strike layer. We can coordinate with our in-house plating partner for a fully finished case.
We are BQUQ, a precision manufacturing factory in Dongguan, China, with 20 years of CNC machining experience. We are not a trading company. You deal directly with the factory owner and the engineering team. That means you get real answers about toolpath feasibility, material availability, and cost reductions. Our precision manufacturing is ISO 9001:2015 certified. We export to the USA, Germany, Japan, and Switzerland. Every shipment includes a Certificate of Conformance and the CMM inspection report. Our made in China pricing is typically 30-40% lower than equivalent Swiss or German machining, without compromising tolerance.
No MOQ — we machine 1 prototype for you, and you can scale up to any quantity later.
Yes, send us the movement drawing or the movement itself, and we will machine the case cavity, stem hole, and dial seat to fit precisely.
We use polished carbide inserts for mirror finish (Ra 0.2 µm) and a 400-grit belt for brushed finish (Ra 0.4 µm), both verified with a profilometer before shipping.
18 days from drawing approval (15 days for 1,000 pcs, plus 3 days for the additional volume).
Send your drawing to sc@bquq.com or WhatsApp +86 13713157787. We will return a firm quote with a confirmed delivery date within 12 hours. Include the case diameter, material grade, and surface finish. We will also send you a DFM (Design for Manufacturing) note if we see a way to reduce cost or improve tolerance.
| Parameter | Capability |
|---|---|
| Materials | AL6061/7075, SUS303/304/316, 45# steel, T2 copper, H59 brass, POM, PEEK, nylon |
| Tolerance | ±0.005mm standard, ±0.003mm on request |
| Machines | 3/4/5-axis CNC, turn-mill, Swiss lathe |
| Surface | Anodizing, nickel, zinc, passivation, sandblast, polish |
| Size Range | Max 400 x 300 x 200 mm |
| Prototype | 72 hours, no MOQ on samples |
| Inspection | Full report per batch, CMM data on request |
