STM-X Knowledge Centre

Spring testing, in plain engineering language.

Practical guides to load–deflection curves, spring rate, preload datum, compression, extension, hysteresis and measurement integrity.

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Written to help you run and review the test

Every guide distinguishes measurement from interpretation, cites applicable sources where relevant and carries a review date. Product links are present, but they do not replace the engineering explanation.

01 Spring testing fundamentals

What is spring testing?

A practical introduction to compression and extension spring testing, the measurements a spring tester records, and what a load-deflection curve reveals.

7 min read Read guide → 02 Curve interpretation

Reading a load–deflection curve

Learn how to interpret seating, the working range, spring rate, peak load, unloading behaviour and anomalies on a spring load-deflection graph.

8 min read Read guide → 03 Calculation guide

Spring rate calculation

Calculate spring rate from two force-deflection points, understand units, and learn why a defined measurement interval is more reliable than a single-point estimate.

8 min read Read guide → 04 Test procedure

Compression spring testing

A practical compression spring test workflow covering fixtures, preload, datum, repetitions, target travel, curve review and reporting.

9 min read Read guide → 05 Test procedure

Extension spring testing

Understand extension spring fixtures, initial tension, the linear rate region, test displacement and safe interpretation of a tension test curve.

9 min read Read guide → 06 Measurement integrity

Preload, datum and displacement

Why machine position and spring test displacement are different, how a preload datum is established, and how the distinction protects traceability.

7 min read Read guide → 07 Curve behaviour

Loading, unloading and hysteresis

What the gap between loading and unloading curves means, how hysteresis energy is represented, and which test or fixture effects to investigate.

7 min read Read guide → 08 Metrology

Calibration and uncertainty

A practical guide to force and position calibration, traceability, machine compliance, fixtures and uncertainty in spring testing.

9 min read Read guide →

Standards context

Use standards as sources, not decoration.

Our guides can explain terminology and practice, but they do not reproduce or replace licensed standards, customer drawings or approved procedures.

ISO 22705-1:2021Compression spring measurement and test parameters →ISO 22705-2:2023Extension spring measurement and test parameters →