If you need to replace a spring, whether it’s broken, worn, or just no longer functional, accurate measurement is essential to ensure the new spring works seamlessly in your application. Measuring a spring might seem tricky, especially if it’s damaged, but with the right steps, you can determine the key dimensions and characteristics.
This guide will walk you through how to measure compression, extension, and torsion springs for replacement.
General Tools You’ll Need
- Calipers: For precise measurements of wire diameter and coil dimensions.
- Ruler or Measuring Tape: To measure the overall length of the spring.
- Scale: To measure the spring’s weight, if necessary.
- Protractor: For torsion springs to measure leg angles.
How to Measure a Compression Spring
A compression spring resists compression and is used to store energy or provide a pushing force.
Key Dimensions to Measure
- Free Length:
- Measure the overall length of the spring in its uncompressed state.
- If the spring is broken, measure the largest intact section.
- Outer Diameter (OD):
- Measure the distance across the outer edges of the coil.
- Inner Diameter (ID):
- Subtract twice the wire diameter from the outer diameter (ID = OD – 2 × wire diameter).
- Wire Diameter:
- Measure the thickness of the wire used to make the spring.
- Use calipers for precise measurement.
- Number of Active Coils:
- Count the number of coils that are free to compress, excluding the closed or ground ends.
- Spring Rate (Optional):
- If you can test it, apply a known force to compress the spring and measure the deflection. Divide the force by the deflection to calculate the spring rate.
How to Measure an Extension Spring
Extension springs stretch to provide resistance and are often used in tension applications.
Key Dimensions to Measure
- Free Length:
- Measure the overall length from one end of the hook or loop to the other.
- Include the hooks or loops in the measurement unless they are damaged and need replacement.
- Outer Diameter (OD):
- Measure the distance across the outer edges of the coil.
- Wire Diameter:
- Use calipers to measure the thickness of the wire.
- Hook or Loop Type:
- Identify the style of the ends (e.g., crossover, side hooks, machine hooks).
- Coil Count and Pitch:
- Count the total number of coils and note the spacing between them.
How to Measure a Torsion Spring
Torsion springs store energy in a twisting motion and are often used in hinges or levers.
Key Dimensions to Measure
- Free Length:
- Measure the length of the spring body, excluding the legs.
- Outer Diameter (OD):
- Measure the outer edge-to-edge distance of the coil.
- Wire Diameter:
- Use calipers to measure the thickness of the wire.
- Leg Length:
- Measure the length of each leg from the center of the coil.
- Leg Angle:
- Use a protractor to measure the angle between the two legs.
- Inner Diameter (ID):
- If needed, calculate by subtracting twice the wire diameter from the outer diameter (ID = OD – 2 × wire diameter).
Tips for Measuring a Broken or Worn Spring
- Use Intact Sections: If part of the spring is broken, measure the largest intact section and extrapolate the missing details.
- Consult Old Specifications: If available, refer to the original design specifications for the spring.
- Take Multiple Measurements: Springs can deform over time, so measure multiple sections and average the results.
- Consult a Professional: If the spring is heavily damaged or the measurements are unclear, provide the broken spring to a manufacturer for analysis.
What to Do After Measuring
Once you’ve gathered the measurements, provide this information to your spring supplier or manufacturer. Be sure to include:
- All measured dimensions.
- Material type, if known (e.g., stainless steel, carbon steel).
- Intended application and operating conditions (e.g., temperature, load requirements).
- Any specific requirements, such as corrosion resistance or load capacity.
Conclusion
Accurate measurements are critical for replacing a spring, as even minor deviations can impact the performance of your application. Whether it’s a compression, extension, or torsion spring, following these steps ensures you can find a replacement that fits perfectly.
If you’re unsure about your measurements or need help designing a replacement, reach out to an experienced spring manufacturer as linspring. With the right guidance, you’ll have a new spring that performs reliably and meets your exact needs.