I. Flat Washer: Increasing Area, Protecting Surfaces
Core Function:
The primary function of a flat washer is to distribute pressure. By increasing the contact area between the bolt head/nut and the surface of the connected part, it achieves the following:
- Protects Soft Materials: Prevents the bolt from crushing or damaging softer connected surfaces like aluminum, plastic, or composite materials during tightening.
- Compensates for Uneven Surfaces: Provides a better bearing surface on slightly angled or uneven surfaces.
- Acts as a Spacer: Can sometimes be used as an adjustment shim.
How to Choose a Flat Washer?
II. Spring Washer: Prevents Loosening, Absorbs Shock, Dynamic Locking
Core Function:
The primary function of a spring washer is to prevent loosening and absorb shock. Its split-ring spring structure creates continuous elastic force after tightening, providing a preload force opposite to the nut's tightening direction, thereby:
- Increasing Friction: Effectively resists nut loosening caused by vibration, impact, or load variations.
- Providing Cushioning: Absorbs some vibrational energy, protecting the connection.
Key Application Points:
- Spring washers are typically not used alone and should be combined with a flat washer.
- The correct installation sequence is: Connected Part → Flat Washer → Spring Washer → Nut. The flat washer contacts the workpiece surface to protect it, while the spring washer provides the anti-loosening force under the nut.
Advantages and Limitations:
- Advantages: Good anti-loosening and shock absorption performance, easy installation, cost-effective.
- Limitations: Its performance highly depends on material and heat treatment processes. Poor-quality spring washers are prone to fracturing and failure. Therefore, sourcing from reputable suppliers is crucial.
III. How to Choose? A Practical Guide Based on Conditions
In practical applications, the selection of washers primarily depends on the specific operating conditions:
- Static, Light Load, No Vibration: Using only a flat washer is sufficient. Its role is to protect the surface and distribute pressure.
- Presence of Vibration, Impact, or Load Variations: The combination of "Flat Washer + Spring Washer" is essential. The flat washer is responsible for protecting the contact surface, while the spring washer primarily provides anti-loosening and shock absorption capabilities.
- Soft or Easily Damaged Base Material: A flat washer must always be used to prevent crushing damage, regardless of whether it is combined with a spring washer.
- Special Performance Requirements (e.g., Conductivity, Sealing): Specialized washers with specific functions, such as copper washers or sealing washers, should be selected directly.
IV. Conclusion & Best Practices
For the vast majority of industrial applications subject to vibration or alternating loads, the combination of a "Flat Washer + Spring Washer" is the optimal and most reliable choice. This combination simultaneously addresses:
- Protection (Flat Washer)
- Anti-Loosening (Spring Washer)
- Vibration Resistance (Spring Washer)
Final Recommendations:
To ensure long-term reliability of the connection, always:
- Clarify requirements based on operating conditions (static/dynamic load, vibration level) and materials (soft/hard).
- Select washers with matching dimensions and appropriate materials.
- Prioritize purchasing washers, especially spring washers, from quality-reliable suppliers. Their heat treatment quality directly affects anti-loosening service life.
Correctly selecting and using washers, though a detail, is a crucial step in ensuring the safety and reliability of the entire mechanical connection
