Heavy Load Duty Compression Die Spring, 8mm-18mm Diameter & Up To 55mm Long JIS

Match the outer diameter to your spring pocket bore and the inner diameter to your guide post diameter. The spring should slide freely over the guide post with a small clearance (typically 0.5–1 mm per side) and fit snugly inside the pocket without binding. For example, a 12 mm OD / 6 mm ID spring suits a 12 mm pocket bore and a 5–5.5 mm guide post.

Under the JIS B 5012 standard, color identifies the load class of the die spring. Within the heavy-load category offered here, the five colors (Yellow, Blue, Red, Green, Brown) correspond to different spring rates and deflection capacities. Check the specific spring rate data for your chosen color/size combination to confirm it meets your force requirements.

Heavy-load die springs are designed to deliver significantly higher spring rates than light (yellow in some standards) or medium-load variants of the same free length and diameter. They are intended for applications requiring high return force with limited deflection — such as stripper plates in stamping dies or spring-loaded clamping fixtures under heavy cutting forces.

The epoxy color coating provides a degree of corrosion protection suitable for typical indoor workshop and toolroom environments. For applications involving direct coolant exposure or outdoor use, consider applying a light machine oil or grease to the spring coils. The chromium-silicon alloy wire also offers better inherent corrosion resistance than plain carbon steel.

Yes. The smaller sizes (8×4 mm and 10×5 mm OD/ID, 15–25 mm free length) are popular for 3D-printer bed leveling, extruder tensioners, and linear-motion return mechanisms. Just verify that the spring rate matches your required preload force — heavy-load springs may be stiffer than needed for very light-duty applications, so check the force curve for your chosen variant.

Select a free length that allows your required working deflection while keeping the spring above its solid height. A common rule of thumb is to operate die springs at no more than 30–40% of their free length in deflection for maximum fatigue life. For example, if you need 10 mm of travel, a 30–35 mm free-length spring is a reasonable starting point, leaving adequate margin above solid height.

Each listing is for one (1) piece. If you need multiple springs for a multi-cavity die or a set of fixtures, simply adjust the quantity at checkout. Buying in multiples ensures color and batch consistency across your tooling.