What This Spring Is and Why Engineers Specify It This is a custom spring manufactured to your exact drawing — compression, extension, torsion, or wire form. We hold wire diameter tolerance to ±0.01 mm
This is a custom spring manufactured to your exact drawing — compression, extension, torsion, or wire form. We hold wire diameter tolerance to ±0.01 mm, free length to ±0.05 mm, and outer diameter to ±0.02 mm. Hardness runs 40–52 HRC depending on material, with surface finish Ra 0.4 on ground ends. Lead time is 7 days for prototypes, 15 days for production runs. This is precision manufacturing, made in China, with no MOQ — you order one piece or one million.
Most springs fail from residual stress left after coiling. We shot-peen every compression spring above 0.5 mm wire diameter. That increases fatigue life by 300% compared to un-peened parts. We also pre-set (compress to solid height) every spring before shipment. This removes initial relaxation, so your spring holds its specified load after the first cycle. If your design calls for a constant force or variable pitch, we CNC coil it — no form tools, no secondary bending error.
We stock 302 stainless (AISI 302), 316 stainless, 17-7 PH, music wire (ASTM A228), oil-tempered chrome silicon (ASTM A401), and beryllium copper. For high-temperature environments, Inconel X-750 is available on request. Heat treatment is done in-house: stress relieve at 260°C for stainless, 400°C for chrome silicon. We do not outsource tempering — that keeps hardness consistent across batches. Surface options include zinc plating (72-hour salt spray), electroless nickel (Ra 0.4), and passivation for medical-grade cleanliness.
| Parameter | Value / Range |
|---|---|
| Wire Diameter | 0.1 mm – 12 mm |
| Free Length | 1 mm – 300 mm |
| Outer Diameter | 1 mm – 80 mm |
| Materials | 302, 316, 17-7 PH, Music Wire, Chrome Silicon, Beryllium Copper |
| Hardness (HRC) | 40 – 52 (dependent on material) |
| Tolerance (Wire Dia) | ±0.01 mm |
| Tolerance (Free Length) | ±0.05 mm |
| Surface Finish (Ground Ends) | Ra 0.4 |
| Runout (Total Indicator Reading) | ≤0.02 mm |
| Lead Time (Prototype) | 7 days |
| Lead Time (Production) | 15 days |
| MOQ | No MOQ |
We check load at specified deflection — not just dimensions. Every spring is tested on a digital force tester with ±1% accuracy. We verify free length, outer diameter, and wire diameter with a CMM (coordinate measuring machine) for runs over 500 pieces. For critical springs, we provide a material certificate (EN 10204 3.1) and a load test report. We reject any part with runout above 0.02 mm — that is our internal limit, stricter than many OEM specs. If your drawing calls for a tighter tolerance, we adjust the coiling process, not the inspection gate.
If your application runs above 150°C, standard music wire will relax and lose load. We recommend chrome silicon or 17-7 PH. For corrosive environments, 316 stainless is the baseline, but we can add a PTFE coating for friction reduction. For high-cycle applications (over 1 million cycles), we switch to shot-peened and pre-set springs — this is standard, not an upsell. Tell us your operating temperature, cycle count, and load requirement. We will select the material and heat treatment, then confirm the spring rate (N/mm) before production.
A spring with poor tolerance will cause noise, binding, or premature failure in your mechanism. We control wire diameter and free length together — because a 0.01 mm change in wire diameter alters spring rate by 8%. Our CNC coiling machines use laser gauging live during winding. This means we correct diameter drift in real time, not after a batch is done. For mating parts, we can also machine the spring seats or retainers in our CNC lathes — one supplier, zero mismatch. Refer to our CNC machining tolerances guide for how we hold ±0.005 mm on mating features.
Send us your drawing (PDF, STEP, or DXF). If you do not have a drawing, send a sample — we reverse-engineer it with our optical comparator and return a drawing for approval. We quote within 12 hours. Prototypes ship in 7 days. Production starts after your approval of the prototype. We do not charge tooling for standard wire sizes. For non-standard wire, we source it in 3 days — this is the only delay you will see. If you are unsure about which material, send us your operating environment and we will advise. For cutting tools used to make these springs, see our CNC cutting tool selection guide — it covers tool geometry for hardened materials.
We grind ends flat and square to 1° maximum. If you need closed and ground ends, we do that at no extra cost up to 5 mm wire diameter. For springs above 5 mm, grinding is done on a double-disc grinder, holding parallelism to 0.02 mm. We also offer reduced coil counts for tighter solid height — this is common in aerospace actuators. Do not assume a stock spring will fit your assembly. We make the spring to your envelope, not the other way around.
We export to 40 countries. Parts over 2 kg ship by DHL Express (3–5 days). Lighter springs ship in padded envelopes with a full inspection report inside. We handle customs paperwork — you receive a single invoice with HS code 732020. For EU and US customers, we provide RoHS and REACH declarations. No MOQ means you can order 10 pieces for a prototype run and scale up later. We do not penalize small orders with setup fees — the price per piece is slightly higher, but the total cost stays low.
No MOQ — we accept 1-piece orders for prototypes and scale to 1 million pieces with the same tolerance.
Yes, we reverse-engineer your sample using an optical comparator and CMM, then produce a drawing for your approval before making any parts.
We use SPC (statistical process control) — sampling every 500 pieces for load, free length, and OD, plus 100% dimensional inspection for any spring with a wire diameter under 0.3 mm.
Prototypes ship in 7 days; for urgent orders, we offer a 72-hour express service for compression springs up to 2 mm wire diameter at a 15% surcharge.
Send your drawing for a firm quote within 12 hours. Email sc@bquq.com or WhatsApp +86 13713157787. We will reply with price, lead time, and a technical review of your spring design.
| 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 |
