What This Coil Spring Delivers in Hard Numbers This is a custom coil spring built from wire diameters 0.1 mm to 12 mm, with a pitch tolerance of ±0.01 mm and a free length tolerance of ±0.05 mm. You g
This is a custom coil spring built from wire diameters 0.1 mm to 12 mm, with a pitch tolerance of ±0.01 mm and a free length tolerance of ±0.05 mm. You get a spring that holds its load within ±3% across 10,000 cycles, surface finish at Ra 0.4 μm, and a hardness range of 45–52 HRC for fatigue resistance. From drawing approval to shipment, your coil spring leaves our Dongguan factory in 15 days, and we run no minimum order quantity (no MOQ) on any custom spring.
Most coil springs fail from residual stress left after coiling, not from material defects. We stress-relieve every spring at 300–350°C for 30 minutes in a nitrogen atmosphere, which removes internal stress and boosts fatigue life by 40% compared to as-coiled springs. For springs under 2 mm wire diameter, we add a shot-peening step at 0.3 A intensity to close surface micro-cracks. Our load testing rig checks force at 25%, 50%, and 75% of total deflection on every batch, so you never get a spring that sags after 1,000 cycles.
We start with four wire grades: music wire (SWP-A) for general use, chrome silicon (SWOSC-V) for high-temperature up to 250°C, stainless steel 302 (SUS302) for corrosion resistance, and Inconel X-750 for exotic applications above 400°C. After coiling, we apply the right heat cycle — for chrome silicon, that means oil quenching at 850°C followed by tempering at 420°C to hit 48–52 HRC. Stainless springs get a 400°C precipitation hardening, not a standard temper, to prevent brittleness. Every heat lot gets a hardness test on a Rockwell tester, and we record the HRC value on the inspection sheet you receive with the springs.
| Specification | Value |
|---|---|
| Wire diameter range | 0.1 mm – 12 mm |
| Free length tolerance | ±0.05 mm (under 50 mm), ±0.10 mm (above 50 mm) |
| Outer diameter tolerance | ±0.02 mm for wire ≤ 2 mm; ±0.05 mm for wire > 2 mm |
| Pitch tolerance | ±0.01 mm (measured over 10 coils) |
| Hardness range | 45–52 HRC (chrome silicon), 42–48 HRC (stainless 302) |
| Surface finish | Ra 0.4 μm (ground ends), Ra 0.8 μm (cut ends) |
| Load tolerance at 50% deflection | ±3% of specified force |
| End types | Closed ground, closed not ground, open, double torsion |
| Lead time | 15 days for standard wire, 20 days for Inconel |
| MOQ | No MOQ — one piece or one million, same process |
| Inspection equipment | Coordinate measuring machine (CMM) + load tester + optical projector |
Runout — the wobble when a spring rotates — kills performance in valve and clutch applications. We hold total runout to 0.02 mm by grinding both end faces parallel to within 0.01 mm on a double-disc grinder. For closed-ground ends, we grind the last 1.5 coils flat to 90° ±1° relative to the spring axis. We check every 50th spring on an optical projector at 20× magnification, measuring the angle between the end face and the spring axis. If you need tighter runout than 0.02 mm, we can grind to 0.01 mm with a 3-day lead time extension.
Every coil spring order ships with a full dimensional report, not a generic certificate. The report lists free length, outer diameter, wire diameter, pitch, total coils, load at three deflection points, and hardness HRC — all measured on actual parts from your batch. We use a CMM for OD and pitch, a digital load tester for force, and a Rockwell tester for hardness. For orders above 500 pieces, we inspect 10 pieces per 1,000 and include the raw data. Springs that fail any spec are scrapped, not reworked, because re-coiling changes grain structure.
Standard coil spring lead time is 15 days from drawing approval to shipment. Need it faster? We keep SWP-A and SUS302 wire in stock in 12 diameters, so prototype springs can ship in 5 days. For production runs above 10,000 pieces, we run two shifts on our CNC coiling machines, which cuts lead time to 10 days without changing inspection steps. We quote exact dates, not ranges — if we say the 15th, the springs are on the truck on the 15th. For material selection and heat treatment details, check our CNC cutting tool selection guide to understand how spring wire interacts with tooling, and our CNC machining tolerances guide for how we hold ±0.01 mm on every dimension.
There is no MOQ — we run single prototypes at the same tolerance and inspection level as million-piece orders, which is why engineers across Europe and North America trust our precision manufacturing from a Dongguan factory.
Yes — send us a physical sample or a drawing with wire diameter, free length, OD, total coils, and load requirements, and we will reverse-engineer the spring and send a free pre-production sample within 7 days.
We test load at 25%, 50%, and 75% deflection on a calibrated load tester, and for high-cycle applications, we run a 10,000-cycle fatigue test on 3 samples per batch and include the results in your inspection report.
Prototypes in SWP-A or SUS302 wire ship in 5 days from drawing approval, and production orders up to 50,000 pieces ship in 15 days — we never quote a longer lead time than we can hold.
Email your coil spring drawing or a photo with dimensions to sc@bquq.com, or message us on WhatsApp at +86 13713157787. We reply with a firm price, exact lead time, and a DFM check within 12 hours — not a vague estimate. Our precision manufacturing, made in China, is backed by 20 years of CNC machining, stamping, and spring production for automotive, medical, and electronics clients. No MOQ, no minimum order value, no surprises. Send your drawing today and get a spring that passes inspection on the first try.
| Parameter | Capability |
|---|---|
| Materials | SUS302/304/316, SWC piano wire, SWP music wire, 65Mn, phosphor bronze, beryllium copper |
| Types | Compression, extension, torsion, wire forms, battery springs, touch springs |
| Wire Diameter | 0.05 - 12.0 mm |
| Tolerance | ±0.02mm standard, ±0.01mm on request |
| Surface | Zinc plating, nickel, black oxide, passivation, shot peening |
| Machines | CNC spring coiling machines, torsion machines, wire forming machines |
| Prototype | 72 hours, no MOQ on samples |
| Inspection | Load test per batch, fatigue test data on request |
