Red Die Springs, 65Mn Rectangular Wire — TM/SWM Medium Load — Pack of 2

Red 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 red is TM — medium load. It sits one class above blue (light) and two above yellow (extra light) in the same dimensional range.

Under ISO 10243, red means heavy — one class higher again. Red is the one colour that shifts by a single step rather than inverting, which makes it easier to get wrong than yellow or green: an ISO red spring and a JIS red spring drop into the same pocket and give you noticeably different force. If your drawing calls out ISO 10243, tell us the load you need and we will confirm the right part rather than matching on 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 red TM:

Design a long-run production tool against the 25.6% figure and treat 32% 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

Red TM, at 32% compression — the 300,000-cycle basis. These values depend on outside diameter alone: a 25 × 100 spring has the same limit load as a 25 × 30. Free length changes the available stroke, not the peak force. For the one-million-cycle basis (25.6%), multiply by 0.8.

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. Least force, most travel.
• Blue — TL, light. The general-purpose middle.
• Red — TM, medium (this page). Ø20 and above only.

When red is the right choice

Red is the class to reach for when you have run out of pocket. If a blue spring of the outside diameter your plate will take cannot generate the force you need, you have two options: go to a bigger outside diameter, or go up a load class at the same diameter. Where the bore is fixed — a stripper plate, an ejector return, a slide retention pocket you cannot enlarge — going up a class is the only route.

The trade is stroke. Red gives you 1.5 times the blue load at the same OD but only 32% compression against blue's 40%, so check your working compression against the limit before you commit rather than after. If you need both force and travel in a fixed pocket, the answer is usually two shorter springs in series or a redesign of the pocket, not a harder spring run near its limit.

Specifications

Red is not made below Ø20 in this range. If you need medium load in a smaller bore, ask — we will tell you honestly whether it exists or whether you are better served by a blue spring at the next diameter up.

Need something else?

Ø50 and Ø60 red, free lengths beyond 100 mm, and green TH heavy-load springs are all 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.

Diagram is dimensional and applies to all colours in this range.