BQUQ’s Stainless Steel Extension Tension Springs Collection 02 is a pre-engineered line of extension springs designed for applications requiring predictable force, fatigue resistance, and tight dimens
BQUQ’s Stainless Steel Extension Tension Springs Collection 02 is a pre-engineered line of extension springs designed for applications requiring predictable force, fatigue resistance, and tight dimensional control. Every spring ships with a tolerance of ±0.01 mm on outer diameter and free length, a surface finish of Ra 0.8 µm, and a minimum hardness of 45 HRC after heat treatment. We quote within 12 hours, ship prototypes in 5 days, and hold a 99.2% on-time delivery rate from our Dongguan factory.
We stock 302 stainless steel wire for all Collection 02 springs because it offers the highest tensile strength (up to 2,100 MPa) among austenitic grades at this wire diameter range. 304 gives you better corrosion resistance but 20% lower fatigue life under cyclic loading. 316 costs more but adds nothing for dry or lightly lubricated environments. For most precision applications—medical devices, aerospace actuators, automotive latches—302 is the correct metallurgical choice. If your design demands saltwater or chemical exposure, we switch to 316 on request with a 2-day schedule adjustment.
Collection 02 hooks are formed with a minimum bend radius of 1.5 times the wire diameter. This is not a default—it is a calculated value that reduces stress concentration at the hook transition by 40% compared to sharp 90-degree bends. We offer four hook styles: full loop, extended hook, cross-over center, and side loop. Each hook is inspected for crack initiation using dye penetrant testing on every 500th piece. Initial tension is set to 5-8% of the maximum load for consistent seating in your assembly, preventing sagging or permanent set after the first cycle.
Each spring in Collection 02 is wound on CNC coiling machines with closed-loop wire feed control. This gives us a spring rate tolerance of ±3% across the full deflection range. For comparison, industry standard is ±10%. We calibrate load at 20%, 50%, and 80% of maximum deflection on a digital force tester (accuracy ±0.5 N) and record the values on the inspection report. If your application needs a specific load at a specific height—say 12 N at 45 mm—we adjust the coil pitch and wire diameter in the CNC program, then verify with a 100% check on the first article.
After coiling, we stress-relieve every spring at 260°C for 30 minutes in a controlled atmosphere oven. This removes residual stress from the forming process and stabilizes dimensions. For springs requiring higher hardness, we use a precipitation hardening cycle that reaches 45-48 HRC while maintaining elongation at break above 40%. The surface is then passivated in a nitric acid bath to remove free iron particles and enhance corrosion resistance—this is mandatory for medical and food-grade applications. No spring is shipped without this two-step treatment.
We use a Keyence IM-8000 optical comparator to measure free length, outer diameter, and hook alignment on a sample of 32 pieces per batch. For critical dimensions, we measure 100% of parts with a digital micrometer (resolution 0.001 mm). Force testing is performed on a custom-built load frame with a 1 kN load cell, calibrated to ISO 376 standards. Our quality lab records all data on a batch-specific certificate. If you order 1,000 pieces, you get one certificate. If you order 100,000 pieces, you get ten certificates—one per sub-batch, so you can trace any defect to its source.
Collection 02 springs are individually wrapped in VCI (vapor corrosion inhibitor) paper to prevent rust during transit, even in high-humidity sea freight containers. We then pack them in rigid cardboard boxes with foam inserts to prevent tangling or deformation. For orders above 10,000 pieces, we use anti-static plastic trays with individual slots—this cuts your assembly time by eliminating untangling. Every box is labeled with a barcode that includes batch number, material grade, and heat treatment date for full traceability.
Collection 02 is a starting point, not a limit. We can change wire diameter from 0.2 mm to 8.0 mm, adjust the number of active coils, or add a nickel coating for higher temperature resistance (up to 300°C). You can also request a closed-ground end for seating in a flat pocket—this is not standard but adds no lead time if we have the wire in stock. Send us a drawing with your load requirements, and our engineers will suggest the exact wire grade and geometry within 24 hours. For help selecting the right tool steel for any mating components, see our CNC cutting tool selection guide.
| Parameter | Value / Range |
|---|---|
| Material | 302 Stainless Steel (AISI), optional 316 or 17-7PH |
| Wire Diameter | 0.2 mm – 8.0 mm |
| Free Length | 5 mm – 300 mm |
| Outer Diameter | 2 mm – 50 mm |
| Hardness | 45 – 48 HRC (after precipitation hardening) |
| Tolerance (OD & Free Length) | ±0.01 mm |
| Surface Finish | Ra 0.8 µm (passivated) |
| Spring Rate Tolerance | ±3% (calibrated at 3 points) |
| Max Operating Temperature | 260°C (302 SS), 300°C (nickel coated) |
| Lead Time (Prototype) | 5 business days |
| Lead Time (Production) | 12-15 business days for 1,000-50,000 pcs |
| MOQ | No MOQ (1 piece accepted for prototype validation) |
Our CNC coiling machines hold repeatability of ±0.005 mm on coil pitch across a 10-hour shift. We monitor this with in-line laser gauges that reject any part outside spec automatically. For orders above 20,000 pieces, we run a control chart (X-bar and R) updated hourly, and we pause production if the trend lines approach warning limits. This is why we can promise a first-article-to-batch deviation of less than 0.02 mm on outer diameter—even when you order 200,000 pieces. If you are comparing our process to traditional forming, read our CNC machining tolerances guide to see the measurable difference.
Every shipment includes a material certificate (EN 10204 3.1) and a dimensional inspection report. The report lists free length, OD, wire diameter, hook alignment (within 1°), and load at 3 specified deflections. We also include a photograph of a representative sample taken under a 10x microscope showing surface finish. If you need a full PPAP level 3 submission, we can provide it for an additional 2 days. Our QC team signs off only when all parameters are within the tolerance bands listed above—no exceptions, no partial approval.
Three factors drive the price of Collection 02 springs: wire diameter (material cost), tolerance class (inspection time), and quantity (setup amortization). For example, a 1.0 mm wire spring with ±0.01 mm tolerance costs $0.08 per piece at 10,000 quantity, but drops to $0.05 at 100,000. If you relax the tolerance to ±0.03 mm, the price falls another 20% because we can use high-speed coiling without the in-line gauge. We always quote both options—the tight tolerance and the standard tolerance—so you can decide based on your actual functional needs.
There is no MOQ. We accept a single piece for prototype validation at a small setup fee, and production orders start from 100 pieces.
Yes—we offer four standard hook styles, plus custom forms like threaded ends or swivel hooks, and coatings such as zinc-nickel or PTFE, with a 2-day addition to the lead time.
We use in-line laser gauging on 100% of parts, plus a 32-piece sample inspection on an optical comparator for every batch, and we provide a full dimensional report with each shipment.
Prototypes ship in 5 business days, and production orders of 10,000 pieces ship in 12-15 business days after drawing approval.
Send us your part drawing, load requirements, and target quantity. Our engineering team will respond with a firm quote, a DFM (Design for Manufacturing) review, and a suggested wire grade within 12 hours. We are a precision manufacturing factory in Dongguan, China, with 20 years of experience in CNC machining and spring forming. All springs are made in China under ISO 9001:2015 controls. No MOQ applies to any custom order. For more on how CNC wire forming beats traditional methods, see our custom spring manufacturing CNC wire forming guide.
Email: sc@bquq.com
WhatsApp: +86 13713157787
Send your drawing today—we reply within 12 working hours.
| 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 |
