This is the BQUQ Stainless Steel Coil Compression Springs Collection: custom-manufactured coil springs from 302, 316, 17-7PH, and Inconel X-750, made in China with CNC coiling and
This is the BQUQ Stainless Steel Coil Compression Springs Collection: custom-manufactured coil springs from 302, 316, 17-7PH, and Inconel X-750, made in China with CNC coiling and full grinding. You g
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This is the BQUQ Stainless Steel Coil Compression Springs Collection: custom-manufactured coil springs from 302, 316, 17-7PH, and Inconel X-750, made in China with CNC coiling and full grinding. You get a spring that holds ±0.01 mm on outer diameter, free length tolerance of ±0.5%, and a maximum working hardness of 72 HRC (for 17-7PH) — with a standard lead time of 7 days for prototypes and 15 days for production runs. No MOQ, so you can order one piece or one million.
How We Control Free Length and Load Within ±0.5%
Most spring failures come from inconsistent free length and load drift. Our CNC coiling machines use closed-loop wire feed with laser measurement every 0.1 seconds. This holds free length tolerance at ±0.5% for wire diameters from 0.1 mm to 12 mm. Load at 50% deflection stays within ±3% of your specified value. We verify this on a digital force tester for every batch — not a sample, every spring.
Materials and Heat Treatment We Use for Corrosion and Fatigue
We start with certified wire: AISI 302 (basic corrosion resistance), AISI 316 (marine and chemical), 17-7PH (high strength with 72 HRC max after precipitation hardening), and Inconel X-750 (up to 600°C continuous service). Each coil goes through stress-relief heat treatment at 260–430°C, depending on material. For 17-7PH, we add a precipitation hardening cycle at 480°C for 1 hour. This gives you a spring that does not sag under cyclic load — tested to 1,000,000 cycles at 80% of max stress.
Surface Finish and Edge Grinding: Ra 0.4 and Square Ends
Rough edges cause stress concentration and premature fracture. We grind both ends flat, achieving squareness within 0.5° of the axis. Surface finish on ground ends is Ra 0.4 µm. On the coil body, we offer either passivated (Ra 0.8) or electropolished (Ra 0.4) surfaces. Electropolishing removes 0.002–0.005 mm of surface layer, eliminating micro-cracks from wire drawing. If you need a specific finish for medical or semiconductor use, tell us — we have 8 finish options.
Custom Ends: Closed, Open, Ground, or Pig-Tail
Standard springs come with closed and ground ends. But your application might need something else. We make open ends for dynamic loading, closed ends for static compression, and pig-tail ends for spring guides. We also offer reduced OD ends (for tight bores) and conical springs where each coil nests inside the next. Our engineers will suggest the end type based on your load direction and space envelope — no extra cost for the recommendation.
Inspection Before Every Shipment: 100% Dimensional Check
We do not ship random samples. Every spring is measured for free length, OD, and wire diameter using a vision measuring system (accuracy ±0.002 mm). Load testing is done on a 5 kN universal tester for 5% of each batch. Material certificates come from the mill and include chemical composition and tensile strength. If you order over 5,000 pieces, we include a full inspection report with histograms of the batch distribution. This is standard, not a paid add-on.
Packing and Anti-Corrosion Protection for Export
Stainless steel still corrodes under salt or humidity. We oil the springs lightly (or use dry film lubricant for cleanroom use) and pack them in anti-static bags with VCI (vapor corrosion inhibitor) paper. For export, we use double-wall cartons with a 15 kg crush strength. If you need individual poly-bagging or color-coded trays for assembly lines, we do that at no extra charge. Each box gets a label with your part number, batch number, and heat number.
How Our CNC Machining Backs Up Spring Precision
Springs alone do not solve assembly problems. If your spring sits in a machined bore or over a shaft, the tolerances must match. Our in-house CNC machining center (20 machines, 4-axis and 5-axis) can produce the mating parts with the same ±0.01 mm tolerance. This means you get a complete assembly — spring and housing — from one factory. For cutting tool geometry that affects spring performance, see our CNC cutting tool selection guide. For general tolerance stacks, read our CNC machining tolerances guide.
Parameter
Specification
Available Materials
AISI 302, AISI 316, 17-7PH, Inconel X-750, Music Wire (optional)
Wire Diameter Range
0.1 mm – 12 mm
Outer Diameter Range
1.0 mm – 150 mm
Free Length Range
2 mm – 500 mm
Hardness (max)
72 HRC (17-7PH), 48 HRC (302/316)
Tolerance (OD)
±0.01 mm (for OD < 10 mm), ±0.02 mm (for OD 10–50 mm)
Tolerance (Free Length)
±0.5%
Surface Finish (Ground Ends)
Ra 0.4 µm
Squareness
0.5° max deviation
Lead Time (Prototype)
7 days
Lead Time (Production)
15 days for 10,000 pcs
MOQ
No MOQ — order 1 piece for testing
What is the minimum order quantity for custom springs?
No MOQ. You can order one spring for prototyping or 100,000 for production — the unit price adjusts based on quantity, but we never refuse small orders.
Can you match an existing spring design from a competitor?
Yes. Send us the physical sample or a drawing with OD, ID, free length, wire diameter, and load at height — we will reverse-engineer it and produce a spring that meets or exceeds the original spec.
How do you ensure quality for springs made in China?
We use 100% dimensional inspection on every piece, load testing on 5% of each batch, and include a material certificate with chemical composition and tensile strength. Our QC process follows ISO 9001:2015.
What is the typical lead time for a custom spring order?
Prototypes ship in 7 days after drawing approval. Production runs (up to 10,000 pieces) ship in 15 days. For urgent needs, we can expedite to 3 days for prototypes at a 10% surcharge.
Get a firm quote within 12 hours. Send your drawing to sc@bquq.com or message us on WhatsApp at +86 13713157787. Include wire diameter, OD, free length, number of coils, and load requirements — we will reply with a complete price and tolerance analysis.
