Aerospace Springs: Wire Specs, Processing and Inspection

Updated October 12, 2026

Spring types and where they are used

A spring is defined by how it is loaded. Compression springs push, extension springs pull from hooks or loops, torsion springs return a rotating arm, and wave springs give compression force in a fraction of the height. In aerospace they show up in valves and regulators, latches and access panels, connector and switch mechanisms, deployment hinges and release devices on spacecraft, and in ground support equipment.

Smalley, a wave spring maker, states that wave springs can reduce spring height by up to 50 percent compared with an ordinary coil spring for the same job, which is why they appear in tight valve and bearing preload stacks. Bearings that springs preload are covered on aerospace bearings.

The specifications that govern springs and spring wire

Most aerospace springs are made to a drawing, with the wire bought to an AMS material spec and the processing to AMS process specs. Small standard springs can be ordered to SAE AS24585 and AS24586.

One correction to a common shorthand: AMS 5699 is not a 17-7 PH spec. It covers a heat resistant nickel alloy whose composition matches the alloy usually sold as X-750, used for springs that must hold load at temperature. 17-7 PH spring wire is AMS 5678. Mixing the two up on a PO buys the wrong alloy.

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How the part number is built

Spring part numbers are rarely self-describing, because most aerospace springs are drawing numbers. Stock catalog numbers from a spring maker do encode the geometry. Lee Spring's published part number guide decodes its extension spring example LE 014 A 01 M as follows.

The same guide carries a footnote buyers should notice: type 302 may be substituted with type 304 at the maker's discretion. That is normal for commercial stock, and it is exactly why a catalog spring does not meet a drawing that calls AMS 5688 type 302 wire unless the maker certifies to it. For flight hardware, put the drawing or AS sheet number on the PO, not a catalog number alone.

Materials and the trade-offs

Choose spring material by temperature, corrosion environment and magnetic or fatigue needs, then let the wire spec carry the requirement.

AMS 5678 describes wire drawn to condition C that is capable of being precipitation heat treated to CH900 after the spring is formed. In practice that means the coiler or a heat treater has to run the aging cycle, and the cert should show it. For background on these alloy families see stainless and specialty steels and nickel superalloys.

Stress relief, set removal and shot peening

Processing after coiling is what turns a coil of wire into a spring that holds its load. Three steps matter on aerospace drawings.

• Stress relief. Lee Spring defines it as a low temperature heat treatment below the point where the metallurgical structure changes, used to relieve stresses from manufacturing. It stabilizes the spring before setting and finishing. For precipitation hardening wire, the aging cycle takes this place and is specified separately. See heat treatment.
• Set removal (presetting or scragging). The spring is compressed beyond its elastic limit in the direction it will work, so it takes its permanent set at the factory instead of in service. Lee Spring notes this can only be done in the direction of the applied force. A spring that later takes set in service has lost free length and load.
• Shot peening. Peening induces compressive residual stress in the outer fibers of the wire, improving fatigue life. Aerospace drawings call AMS 2430, or AMS 2432 when computer monitored peening is required, with intensity and coverage.

Plating needs care. Lee Spring states that plated springs must be baked immediately after plating to drive out hydrogen. High strength spring wire is exactly where hydrogen embrittlement bites, so name the plating spec, the bake and the time limit; our surface finishing page covers relief baking.

Inspection of load and rate

A spring is accepted on measured load at a stated height or length, not on rate alone. Good drawings give one or two load points with tolerances, the free length as reference, and the solid height or maximum deflection.

• Lee Spring publishes plus or minus 10 percent on spring rate for its stock compression and extension springs and for MS24585 and MS24586 parts, and plus 5 percent with no lower limit on solid height for stock compression springs. Drawing tolerances for flight parts are usually tighter and are set by the designer.
• For torsion springs, load is checked at a stated radius, with load equal to torque divided by radius.
• Wave springs may take a set if compressed below their working height, so a test that bottoms them can damage them.
• Test on a calibrated load tester, after presetting, in the direction of use, and record actual readings on the cert for each lot sampled.

For first production lots, an AS9102 first article ties each drawing characteristic, including load points, to a measured value.

Documentation and ordering checklist

• Drawing number and revision, or AS24585 or AS24586 dash number at its revision.
• Wire spec and condition (AMS 5112, AMS 5688, AMS 5678 with aging to CH900, AMS 5699), with mill certs and heat or lot traceability to the coiled springs.
• Processing: stress relief or aging, set removal, shot peening to AMS 2430 or AMS 2432 with intensity, and passivation or plating by spec with the embrittlement bake.
• Load test points, sample size and recorded results on the cert.
• Certificate of conformance; see certificate of conformance and material certs and traceability.
• DFARS specialty metals for DoD items; steel and nickel and cobalt alloy wire are covered. See DFARS specialty metals.
• Packaging that prevents tangling: extension springs and small compression springs bagged or tubed by lot.

Counterfeit and quality risks, and how to receive springs

The usual failure is substitution rather than an outright fake: 304 for 302, commercial wire for AMS wire, an unpeened spring where the drawing says peened, or a missed embrittlement bake. None of these is visible. That makes traceability from wire heat to spring lot, and a source that will certify the processing, the real control. Apply SAE AS6174 counterfeit materiel controls and our counterfeit parts avoidance process to anything not bought from the maker or its authorized channel.

At receiving, check wire diameter, OD or ID, free length and end configuration, run the drawing load points on a sample, look for peening coverage where it is required, and confirm the cert lists the wire spec, heat, processing specs and load results. Hold any lot whose cert omits the bake for plated high strength springs. Our receiving inspection guide covers sampling and MRB.

How we source springs

We do not stock springs or publish prices. We source standard AS24585 and AS24586 springs through authorized channels, and we have drawing springs made by qualified spring makers with the wire, processing and test requirements flowed down, then deliver them with the maker's certs and our certificate of conformance. Springs often ride with valves, latches, GSE mechanisms and machined housings, so we can put them on one PO with those parts or kit them by assembly. For legacy springs with no current source, we can have them made to print from your drawing, as described under obsolete aerospace parts. See also bushings, spherical bearings and rod ends, the motion category and the parts index.

Get springs made or sourced

Send the drawing or AS dash numbers, quantity, wire spec, processing and load test requirements. We return a source, lead time and the document package. Request a quote for springs.

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Related

• Aerospace Bushings: Standard Sleeves, Liners and Bronze
• Aerospace Ball Bearings: Specs, Materials and Ordering
• Spherical Plain Bearings and Rod Ends for Aerospace

Sources

• SAE: AMS 5112N carbon steel music wire
• SAE: AMS 5688 type 302 spring temper wire
• SAE: AMS 5678 17-7 PH spring temper wire
• SAE: AMS 5699H nickel alloy spring wire
• SAE: AS24585 helical compression springs
• SAE: AMS 2430 shot peening
• SAE: AMS 2432 computer monitored shot peening
• Lee Spring: military specification springs
• Lee Spring: technical glossary
• Lee Spring: engineering notes and tolerances
• Lee Spring: part number guide
• Smalley: wave springs