Yellow Die Springs, 65Mn Rectangular Wire — TF/SWF Extra Light Load — Pack of 2

Yellow rectangular-wire die springs in 65Mn spring steel, electrophoretic-coated, for mold and die maintenance or replacement. Sold in packs of 2. Sizes are given as outside diameter × free length in millimetres.

Load class — read this before ordering

These springs follow the JIS-style colour system, where yellow is TF — extra light load. It is the softest class in this range.

Under ISO 10243, yellow means extra heavy — the opposite end of the scale. Yellow and green are exact inversions between the two systems, so if your drawing or your existing tool calls out an ISO yellow spring, these are nothing like a drop-in replacement. When the colour and the drawing disagree, work from the load values, not the colour.

Maximum compression depends on the life you need

Compression limits are quoted against a cycle count, and confusing the two figures is the commonest reason die springs fail early. For yellow TF:

Design a long-run production tool against the 40% figure and treat 50% as a short-life limit rather than as headroom. The solid figure is a reference for clearance calculations, not an operating condition. A spring that comes out of the tool shorter than its original free length has already been over-compressed and will not recover.

Maximum compression load by outside diameter

Yellow TF, at 50% compression — the 300,000-cycle basis. These values depend on outside diameter alone: a 10 × 100 spring has the same limit load as a 10 × 20. Free length changes the available stroke, not the peak force. For the one-million-cycle basis (40%), multiply by 0.8 — so a Ø16 spring rated 21 kgf here is 16.8 kgf if you are designing for a million cycles.

Note the inside diameters: yellow uses a thinner wire than blue or red at the same outside diameter, so at Ø20 and Ø25 the bore is larger (11 and 13.5 mm) than the blue and red equivalents (10 and 12.5 mm). If you are fitting the spring over a pin, check the ID for the colour you are actually ordering rather than assuming it carries across the range.

These are limit values. For a working design, keep normal operating compression well below the limit — running at the maximum shortens fatigue life sharply.

Same size, different load class

All three colours we stock share outside diameters and free lengths, so they are dimensionally interchangeable at the same OD. What changes is the force and the usable stroke. At Ø25, for comparison: yellow gives 50 kgf at 50% compression, blue 84 kgf at 40%, red 125 kgf at 32%. More force, less travel, in that order.

• Yellow — TF, extra light (this page). Least force, most travel. The right answer when you need stroke in a shallow pocket.
• Blue — TL, light. The general-purpose middle.
• Red — TM, medium. Most force, least travel. Ø20 and above only.

Specifications

Choosing a size

Check outside diameter against your bore, inside diameter against any pin the spring sits over, free length against your installed height, and confirm the working compression your application needs falls inside the limit for the cycle life you are designing to. If you are replacing an existing spring, matching outside diameter, free length and colour is usually enough — but check that the old spring was specified under the same colour system before you rely on the colour alone.

Need something else?

Ø6, Ø14, Ø18, Ø22 and Ø27, free lengths to 300 mm, and heavier classes are available. Request a quote with your size, required load and expected cycle life, and we will come back within one business day.

Shipping

International freight is calculated on packed chargeable weight. See Shipping & Delivery for destinations and transit times. Import duties and taxes are the buyer's responsibility — please read the duties section on that page before ordering.

Packaging images are illustrative. Actual protective materials and carton format vary with size, quantity and shipping route.