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Engineers, makers, and DIY builders who need a dependable compression spring for load-bearing or return-force applications often struggle to find a single source that covers the full range of wire diameters and outer diameters in one consistent length. These 305mm long compression coil springs are designed for exactly that — a standardized free length that fits a wide variety of mechanical assemblies without custom fabrication.
Each spring is wound from round wire stock with a free length of 305mm (approximately 12 inches). Wire diameters span 4mm to 14mm and outer diameters range from 18mm to 90mm (roughly 0.71" to 3.54"). Two material options are available: spring steel for general-purpose mechanical use, and stainless steel for environments requiring enhanced corrosion resistance. End coils are closed and ground for flat, stable seating.
Typical applications include CNC router Z-axis return mechanisms, industrial press tooling, robotic arm counterbalance assemblies, agricultural equipment linkages, and heavy-duty drawer or gate return systems — all scenarios where a consistent 305mm free length and precise wire-to-OD ratio are critical for predictable spring rate performance.
Consistent 305mm (≈12") free length across all variants simplifies design calculations and drop-in replacement for standard mechanical assemblies.
Wire diameters from 4mm to 14mm paired with outer diameters from 18mm to 90mm give you precise spring rate control across light to heavy-load applications.
Choose spring steel for cost-effective general use or stainless steel for corrosion-resistant performance in humid, outdoor, or washdown environments.
Both ends are closed and ground flat, ensuring stable, perpendicular seating on spring plates and machined bores — reducing lateral deflection under load.
Uniform coil pitch throughout the active coil length delivers linear force-deflection behavior, making these springs predictable for engineering calculations.
Suited for CNC machines, robotic actuators, press tooling, agricultural linkages, and heavy-duty return mechanisms where a standardized 305mm spring is required.
| Free Length | 305 mm (≈ 12.0 in) |
|---|---|
| Wire Diameter Range | 4 mm – 14 mm |
| Outer Diameter Range | 18 mm – 90 mm (≈ 0.71" – 3.54") |
| Inner Diameter | See variant options |
| Material | Spring steel / Stainless steel (see variant options) |
| End Type | Closed and ground |
| Coil Direction | Right-hand |
| Spring Rate | See variant options |
| Surface Finish | Natural / uncoated |
| Quantity per Order | 1 pcs (see variant options) |
Measure the inner diameter of your spring housing or bore, then select an outer diameter (OD) that provides a small clearance — typically 0.5mm to 2mm smaller than the bore ID. If you are using a guide rod, the spring's inner diameter (OD minus 2× wire diameter) should be at least 0.5mm larger than the rod OD to allow free movement without binding.
Spring steel offers a higher elastic modulus and is the standard choice for dry, indoor mechanical applications where cost efficiency matters. Stainless steel provides significantly better corrosion resistance, making it the right choice for outdoor equipment, food-processing machinery, marine environments, or any application exposed to moisture, chemicals, or humidity over time.
Yes. The 305mm free length and closed-ground ends make these springs well-suited for CNC router Z-axis return mechanisms and bed-leveling spring assemblies on larger 3D printers. Select a wire diameter and OD combination that matches your guide rod diameter and the load your axis needs to counterbalance. The linear spring rate behavior supports repeatable positioning.
Load capacity varies by wire diameter and outer diameter combination. Larger wire diameters (e.g., 10mm–14mm) with smaller OD-to-wire-diameter ratios produce stiffer springs capable of handling heavier loads. Lighter wire diameters (4mm–5mm) are suited for lighter return-force applications. For precise spring rate and load data for a specific variant, contact us to confirm before ordering for critical load-bearing applications.
Yes — closed and ground ends ensure the spring sits flat and perpendicular on its seat. This reduces lateral (side) deflection under compression, which is important for maintaining alignment in guided spring assemblies. If your application uses a spring plate or machined pocket, ground ends provide a stable, consistent contact surface that unground ends cannot.
For outdoor or corrosive environments, select the stainless steel material option. Stainless steel compression springs resist rust and oxidation in humid, wet, or mildly chemical environments. Spring steel variants are not recommended for prolonged outdoor exposure without additional protective coating, as they can develop surface rust over time.
Verify three dimensions: (1) free length — confirm 305mm fits your uncompressed travel space; (2) outer diameter — must clear your housing bore with a small gap; (3) inner diameter (OD minus 2× wire dia) — must slide freely over your guide rod if one is used. Also confirm the compressed length at your maximum deflection does not reach solid height, which would cause coil bind and potential damage.
