Die Spring Colour Code Chart — Light, Medium, Heavy & Extra-Heavy
Quick answer: Die springs are colour-coded by duty (load) level — commonly light, medium, heavy and extra-heavy — but the exact colour used for each duty level is not identical across every standard or manufacturer, so always confirm against the specific catalogue rather than colour alone.
By Gurudatta Trading Co., Mumbai · Updated 2026-09-29
The four duty levels
Die springs (rectangular-wire compression springs used in press tools, dies and moulds) are grouped into four duty levels based on how much load they carry for a given amount of compression:
- Light duty — lowest spring rate for the size, used where minimal force is needed
- Medium duty — the most common general-purpose rating
- Heavy duty — higher force for the same envelope size
- Extra-heavy duty — highest force, for compact, high-tonnage tooling
Why we don't print a single universal colour table
Different die spring standards and manufacturers (ISO 10243, JIS B5012, and various oval-wire/American systems) use different colours for the same duty level, and even within ISO-style ranges, catalogues vary — for example, medium duty is widely shown as blue and heavy duty as red, but light and extra-heavy are shown differently across sources. Relying on colour alone across different suppliers can lead to fitting the wrong spring. The reliable approach is to match by duty level and dimensions (hole diameter, rod diameter, free length) shown in the specific catalogue or stamped on the spring, not colour alone.
What to send us
Tell us the hole/bore diameter, rod diameter, free length and the required duty level (or the working load if you know it), and we will match or manufacture the correct die spring.
Need springs made to your specification?
Gurudatta Trading Co. (Mumbai, since 2000, ISO 9001:2015) manufactures compression, extension and torsion springs to drawing or sample. Use the free Spring Rate Calculator or message us on WhatsApp.
FAQs
Does die spring colour mean the same thing for every brand?
Not always — colour-to-duty mapping can differ between standards and manufacturers, so confirm the duty level and dimensions rather than relying on colour alone.
What does medium duty mean for a die spring?
It is a mid-range spring rate for a given size, suited to general press-tool use, between light and heavy duty options.
How do I order a die spring without knowing its colour code?
Send the hole diameter, rod diameter, free length and required duty or working load — we can match or manufacture from those dimensions.