English
Washers are small but critical components used in fastening systems to improve stability, distribute pressure, and prevent loosening. In many mechanical assemblies, both a Flat washer and a lock washer are used together to achieve better performance. Understanding how to use lock washer and flat washer correctly can help improve connection reliability and extend the service life of Bolts and screws.
This article explains the functions of these washers, the correct installation order, common materials, and practical applications.
What Is a Flat Washer?
A flat washer is a thin circular plate with a hole in the center that is placed between a bolt head or nut and the surface being fastened. Its main purpose is to distribute the load over a larger area and prevent damage to the surface.
Common types include:
stainless steel flat washers
carbon steel washers
brass or copper washers
custom-designed washers
Flat washers come in various sizes such as 3 8 flat washer, 3 4 flat washer, and m5 washer, depending on the bolt size used in the application.
Many industries also use Custom Flat Washers when specific dimensions, thicknesses, or materials are required for specialized equipment.
What Is a Lock Washer?
A lock washer is designed to prevent bolts or nuts from loosening due to vibration or movement. Unlike a standard flat washer, lock washers provide additional tension or friction that helps maintain the tightness of a fastener.
Lock washers are commonly used in:
automotive assemblies
machinery
electrical equipment
industrial structures
When used together with stainless steel washers or other flat washers, they create a more secure fastening system.
How to Use Lock Washer and Flat Washer Together
The correct installation order is important when combining these two washers. If installed incorrectly, they may not function properly.
Correct Washer Order
When installing a bolt and nut connection, the typical sequence is:
Bolt head → Flat washer → Lock washer → Nut → Fastened material
This means the flat washer should sit directly against the surface being protected, while the lock washer sits between the flat washer and the nut.
Why This Order Matters
The flat washer distributes the pressure from the bolt or nut evenly across the surface. Without it, the lock washer could dig into the material and cause damage.
The lock washer then applies tension to prevent the nut from loosening. This combination ensures both surface protection and vibration resistance.
Understanding how to use lock washer and flat washer in this order is essential for secure fastening.
Common Materials for Flat Washers
Flat washers can be manufactured using different materials depending on strength, corrosion resistance, and application requirements.
Carbon Steel
Many flat washer products are made from high-quality carbon steel materials such as:
65Mn
S45C
S50C
SK7
SK5
These materials offer strong mechanical properties and are widely used in high-strength applications.
Advantages
Stable stamping performance
High hardness
Suitable for high-load structures and internal rotating shafts
Disadvantages
Poor corrosion resistance
Can rust easily in outdoor environments
Magnetic properties may interfere with signals in sensitive equipment
After manufacturing and burr removal, carbon steel washers often receive surface treatments such as:
eco-friendly nickel plating
chemical nickel plating
black oxide coating
zinc-nickel alloy plating
These treatments improve durability and corrosion resistance.
Stainless Steel
stainless steel washers are commonly used for applications requiring corrosion resistance.
Advantages
Excellent rust resistance
Non-magnetic properties
Suitable for visible components or exterior applications
Disadvantages
Lower stamping production efficiency
Slightly lower strength and service life compared with carbon steel washers in high-load mechanical structures
For many industrial applications, stainless washers are preferred when equipment operates in humid or outdoor environments.
Copper
Copper washers are less common but still useful in certain applications.
Advantages
Good corrosion resistance
Suitable for friction between two moving parts with low hardness
Disadvantages
Shorter service life
Not suitable for high-load or high-strength rotating shafts
Common Washer Sizes
Flat washers are produced in many sizes to match different bolt diameters. Some commonly used examples include:
m5 washer for small electronics or precision equipment
3 8 flat washer for medium mechanical assemblies
3 4 flat washer for heavy-duty structural applications
For specialized equipment, manufacturers can also provide Custom Flat Washers designed according to customer requirements.
Washer Tolerance and Precision
High-quality washers require precise manufacturing tolerances to ensure proper fit and performance.
Typical tolerance standards include:
Inner hole tolerance: 0.03–0.05 mm
High-precision products: within 0.02 mm
Outer dimension tolerance: 0.05–0.10 mm
Thickness tolerance: usually within 0.05 mm
For stricter applications, some washers can achieve thickness tolerances of 0.03 mm or less.
These precision standards ensure that stainless steel flat washers and other washer types function reliably in mechanical systems.
Applications of Flat and Lock Washers
The combination of lock washers and flat washer components is widely used in many industries:
Automotive Industry
They prevent bolts from loosening due to vibration in engines and chassis structures.
Industrial Machinery
Machines often use stainless steel washers and lock washers to secure moving components.
Electronics and Equipment Assembly
Small washers such as m5 washer sizes are commonly used in electronic housings and control systems.
Construction and Structural Engineering
Large washers like 3 4 flat washer sizes distribute heavy loads in structural connections.
Conclusion
Knowing how to use lock washer and flat washer correctly is essential for creating secure and long-lasting mechanical connections. The flat washer protects surfaces and distributes pressure, while the lock washer prevents loosening caused by vibration or movement.
By selecting the appropriate materials—such as carbon steel, stainless steel flat washers, or copper—and using the correct washer sizes like 3 8 flat washer or m5 washer, engineers and technicians can ensure reliable fastening performance in various applications.
Whether used in automotive systems, machinery, or structural assemblies, high-quality custom flat washers and properly installed lock washers provide a simple yet highly effective solution for stable mechanical connections.
