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When a mechanism fails because a tiny spring loses its tension or corrodes, the entire assembly stops working. Engineers, hobbyists, and repair technicians who work with miniature mechanisms, precision instruments, and compact assemblies need small compression springs they can rely on — springs that hold their rated load cycle after cycle without deforming or rusting.
These compression springs are wound from 304-grade stainless steel wire with a diameter of 0.4mm. Outer diameters span 2mm to 12mm (approximately 0.08 in to 0.47 in), and available lengths range from 5mm to 120mm (approximately 0.20 in to 4.72 in). Each spring features open, ground-flat ends for stable seating and consistent load distribution across the coil body.
Typical use cases include replacement springs for pen mechanisms and retractable tools, return springs in miniature valves and solenoids, and preload springs in optical or electronic assemblies where a small compression spring with a 2–12mm OD is required for consistent axial force.
Wound from 304-grade stainless steel wire for reliable corrosion resistance in humid, wet, or mildly acidic environments — a step up from carbon steel alternatives.
Consistent 0.4mm wire gauge across all size options ensures predictable spring rates and uniform coil spacing for repeatable performance in precision assemblies.
Eleven outer diameter options from 2mm to 12mm let you match the spring to your bore or housing without custom fabrication.
Choose from lengths as short as 5mm up to 120mm to suit shallow recesses or deeper spring pockets in your design.
Available in packs of 5 or 10 pieces so you can stock spares for prototyping, repair work, or small-batch production without over-ordering.
Ground-flat end coils provide a stable, perpendicular seating surface that reduces side-load and keeps the spring aligned under compression.
| Material | 304 Stainless Steel |
|---|---|
| Wire Diameter | 0.4mm (approx. 0.016 in) |
| Outer Diameter (OD) | 2mm – 12mm (approx. 0.08 – 0.47 in) — See variant options |
| Inner Diameter (ID) | See variant options |
| Free Length | 5mm – 120mm (approx. 0.20 – 4.72 in) — See variant options |
| End Type | Open, Ground Flat |
| Wind Direction | Right-hand (typical for this wire gauge) |
| Spring Rate | See variant options |
| Surface Finish | Natural stainless (no coating) |
| Pack Quantity | 5 pcs or 10 pcs — See variant options |
Measure the inner diameter of the bore or housing where the spring will sit. The spring's outer diameter should be slightly smaller than the bore ID — typically 0.1mm to 0.3mm clearance — to allow free compression without binding. Use the ID value shown in the variant name (e.g., "ID:1.2" for the 2mm OD spring) as a reference for the approximate inner diameter of that spring.
Select a free length that is longer than your required compressed length plus the travel distance. As a starting point, the free length should be at least 20–30% longer than the maximum compressed height in your assembly. If you need a specific spring rate, contact us to confirm the rate for your chosen size combination.
Yes. 304 stainless steel offers good resistance to oxidation, moisture, and mild chemical exposure. It is suitable for indoor mechanisms, light outdoor use, and environments with occasional water contact. For highly aggressive chemical or saltwater environments, 316 stainless steel would be a stronger choice.
304 stainless steel retains adequate mechanical properties up to approximately 300°C (572°F) for short-term exposure. For continuous high-temperature service above 200°C, consider a high-temperature alloy spring. For most room-temperature and moderate-heat applications these springs perform reliably.
The pack quantity affects the per-unit cost and the total number of springs you receive. The 10-piece pack is available for shorter lengths (5mm–50mm) and offers a lower per-piece cost, making it suitable for prototyping or stocking spares. The 5-piece pack covers longer lengths (55mm–120mm) where individual spring weight and material cost are higher.
Spring rate depends on wire diameter, OD, free length, and number of active coils. Because this product covers a wide range of size combinations, specific spring rate values are not listed in the product page. If your application requires a confirmed spring rate, please contact us with your selected size (OD, free length) and we will provide the calculated rate or direct you to a matching specification.
Yes. The smaller OD options (2mm–4mm) with shorter free lengths (5mm–20mm) are well-suited for pen cartridge return springs, retractable tool mechanisms, and similar compact click-action assemblies. The 304 stainless material resists the ink and solvent exposure common in writing instruments.
