Compression Spring FAQs

Compression springs are helical, open-coiled mechanical components that resist compressive forces by shortening under load. When compressed, they store mechanical energy, then release it as they return to their free (unloaded) length. These springs are widely used wherever a pushing or load-bearing force must be countered.

Compression springs differ from extension or torsion springs in several ways:

• Load mode: Compression springs resist pushing/squeezing, whereas extension springs resist pulling/tension and torsion springs resist twisting.
• Coil spacing: Compression springs have space between coils when unloaded; extension springs have coils touching under no load (initial tension).
• Applications: Compression springs are used in situations requiring cushioning, shock absorption, load management, or maintaining force between two surfaces.

When selecting compression springs, consider:

1. Load requirements (max and working) and deflection range.
2. Free length, solid length, and maximum compressed length.
3. Wire diameter and coil diameter.
4. Number of coils (active coils) and spring index.
5. Material and environmental exposure (corrosion, temperature).
6. End style and finish.
7. Expected cycle life and fatigue.
   Using a spring selection guide or consulting engineering support helps ensure the chosen spring meets performance, safety, and cost goals.

Need more information on finding the right spring? Our engineering experts put together a full selection guide complete with design information, details on spring end types, and other characteristics you should look for in your part.

View the Compression Spring Selection Guide

The spring rate (or stiffness) of a compression spring is the force needed to compress it by a unit length (e.g., lbs/in or N/mm). Calculation depends on several variables: wire diameter, coil diameter, number of active coils, material modulus, and sometimes pitch. The maximum load and deflection must be considered to ensure the spring does not deform plastically or buckle.

Compression springs are made from various materials depending on required strength, corrosion resistance, fatigue life, and environmental exposure. Common materials include:

• Music wire for high fatigue strength and low cost.
• Stainless steel (e.g. 302/304, 316) when corrosion resistance is needed.
• Alloys like Inconel, Hastelloy, or titanium for high temperature, chemical exposure, or aerospace/military specs.

Finishes or coatings help protect compression springs (and enhance performance) by reducing corrosion, friction, or wear. These can include:

• Black oxide, zinc or nickel plating
• Passivation (for stainless steel)
• Powder coatings or special epoxy coatings
• Color-coding for identification
  Choosing the correct finish depends on the environment (humidity, chemicals, temperature) and application requirements.

Compression springs can have various end styles to optimize fit and function:

• Open ends – coils end without modification.
• Closed ends – final coil is closed to provide a flat surface.

• Closed and ground ends – after closing, ends are ground to make them flat, stable, and more precise in seating.
   

  The end type affects how the spring seats against surfaces, its solid height, load distribution, and stability under compression.

The life of a compression spring depends on load cycles, material, amplitude of deflection, environmental factors, and design. Key influencing factors include:

• Maximum compression vs. working compression (avoiding over-compression)
• Material fatigue limits
• Corrosion or exposure to harsh chemicals or temperatures
• Manufacturing quality (surface finish, heat treatment, shot peening)
  Well-engineered compression springs, under correct use and maintenance, can last millions of cycles.

Looking for ways to improve the fatigue life of your springs? Watch this informational webinar to learn tips and tricks.

Compression springs are used across many industries. Some examples include:

• Automotive (valve springs, suspension, dampers)
• Aerospace (landing gear, control surfaces)
• Industrial machinery (valve actuators, seals, springs in assemblies)
• Electronics and instrumentation (buttons, pressure sensors)
• Consumer products (pens, appliances, toys)

Steps to Ensure Accurate Measurements

1. Hold the base of the spring in one hand, and the calipers in the other hand.
2. Place the calipers on the outside of the last coil, measuring the largest dimension. This is called the Outside Diameter (O.D.).
3. Place the calipers on the wire in the center of the spring. This is called the Wire or Material Size. You should also measure the wire toward one end for comparison and accuracy.
4. Place the calipers on the full length of the uncompressed spring. This is called Free Length.
5. Count the total coils, beginning at one end, just next to where the wire has been cut. Be sure you count all coils, including any portion of a coil. (see diagram for example)