Locking washers are small, simple parts. But they do a big job. They help keep nuts and bolts tight. They stop parts from coming loose. This keeps machines, vehicles, buildings, and tools working safely and correctly.
In this guide, you’ll learn what locking washers are, how they work, where they are used, and which type to choose.
What Is a Locking Washer?
A locking washer is a disc with a hole in the center. It goes between the nut or bolt head and the surface. It uses friction, tension, or mechanical grip to stop movement.
Locking washers help prevent:
- Nuts from loosening due to vibration
- Bolts from backing out under load
- Damage caused by loose parts
They are a low-cost way to improve safety and reliability.
How Locking Washers Work
- Tension washers create spring pressure to hold fasteners tight.
- Tooth washers bite into surfaces to stop rotation.
- Tab washers lock in place using a physical barrier.
- Some use chemical grip or combine with nuts for extra hold.
Locking washers resist movement from:
- Vibration
- Shock
- Rotation
- Temperature changes
- Repeated load cycles
Types of Locking Washers (With Features)
1. Split Lock Washer
Also called a spring washer. It has a single cut and is twisted.
- Applies spring force to the nut or bolt.
- Common in general-purpose machinery.
- Not ideal for high-vibration jobs.
Strength: Medium
Reuse: Not recommended
2. Tooth Lock Washer
Has teeth that grip the surface. Two kinds:
- Internal Tooth: Teeth on the inside edge
- External Tooth: Teeth on the outside edge
They are good for vibration control. External types grip better than internal ones.
Strength: Good
Use: Electrical, automotive, mechanical
Reuse: Limited (teeth wear down)
3. Flat Lock Washer
Flat washers do not lock parts by themselves. But they can help spread load and protect surfaces. When used with a lock nut or adhesive, they help with tightness.
Strength: Low
Use: Load distribution
Note: Not a locking washer on its own
4. Tab Washer
Has a small metal tab that fits into a slot or groove. Some have side tabs that bend up to lock into bolt faces.
- Used in engines, transmissions, and gearboxes
- Good for large rotating equipment
Strength: Very Good
Use: Heavy equipment, long-term installs
Reuse: Sometimes (depends on design)
Common Materials and Benefits
| Material | Strength | Rust Resistance | Use Cases |
|---|---|---|---|
| Steel | High | Low | General hardware |
| Stainless Steel | High | High | Marine, outdoor, food |
| Brass | Medium | Medium | Electronics, gas valves |
| Plastic/Nylon | Low | High | Lightweight parts, electronics |
Choose material based on environment, load, and rust exposure.
Environmental Resistance
| Material | Temperature Range (°C) | Notes |
|---|---|---|
| Steel | -50 to +300 | Not rust-resistant |
| Stainless Steel | -200 to +870 | Great for harsh conditions |
| Brass | -100 to +200 | Non-sparking, softer |
| Plastic | -40 to +120 | Light duty only |
Vibration Resistance Ratings
| Washer Type | Resistance |
|---|---|
| Flat (alone) | Low |
| Split | Medium |
| Internal Tooth | Good |
| External Tooth | Better |
| Tab Washer | Best |
| Nylon Insert Nut | Best |
| Thread Locker | Best |
Note: Actual performance depends on bolt size, load, and surface condition.
Installation: Step-by-Step
- Choose the correct washer for the bolt and application.
- Clean the surface before placing the washer.
- Place the washer under the nut or bolt head.
- Apply torque using a calibrated tool.
- Make sure the washer sits flat and does not shift.
- For tab washers, bend the tab securely into position.
Torque Reference Table (Metric Bolts)
| Bolt Size | Thread Pitch | Steel Torque (Nm) | Stainless Torque (Nm) |
|---|---|---|---|
| M4 | 0.7 mm | 2.9 | 2.5 |
| M6 | 1.0 mm | 10 | 9 |
| M8 | 1.25 mm | 25 | 22 |
| M10 | 1.5 mm | 50 | 44 |
| M12 | 1.75 mm | 85 | 75 |
Use manufacturer data for exact specs.
Cost vs Performance
| Washer Type | Price | Durability | Application Type |
|---|---|---|---|
| Split Lock | Low | Medium | Light-duty, DIY |
| Tooth Lock | Medium | High | Automotive, electronics |
| Tab Washer | High | Very High | Engines, industrial |
| Nylon Nut | Medium | Very High | Machinery, automation |
Paying more upfront often saves on future repairs.
New Alternatives and Technologies
- Nylon-Insert Lock Nuts: Work well with flat washers
- Thread Locking Fluids: Like Loctite; resist vibration
- Pre-assembled Sets: Bolt + washer + nut combos for quick install
- Serrated Flange Bolts: Combine washer-like grip into the bolt head
Choose based on your speed, space, and strength needs.
Industry Standards
| Standard | Region | Coverage |
|---|---|---|
| DIN 127 | Germany | Split Lock Washers |
| DIN 6798 | Germany | Tooth Lock Washers |
| ISO 7089 | Global | Flat and load washers |
| ASME B18.21.1 | USA | Locking washer types |
Always follow the correct standard for safety and compliance.
Maintenance and Inspection Tips
- Check washers during regular service
- Replace any that are rusted, bent, or worn
- Do not reuse split or tooth washers
- Clean dirty or corroded areas
- Re-torque fasteners if loosened
Real-Life Examples
Failure:
A conveyor belt failed due to loose bolts. It used only flat washers. After replacing them with external tooth washers, the system stayed secure under vibration.
Success:
A marine boat used stainless tab washers on the engine mounts. Even after 18 months of heavy sea use, no bolt came loose.
Frequently Asked Questions (FAQ)
Can I reuse locking washers?
Most locking washers are designed for one-time use. Split and tooth types deform. Reusing them can reduce performance.
Do I need a locking washer with a nylon lock nut?
No, usually not. Nylon lock nuts already resist vibration. But for added security, some use both.
Can I use a locking washer with a flat washer?
Yes. Place the flat washer first (to spread load), then the locking washer next to the nut or bolt.
Are locking washers better than thread locker fluid?
Both work well. Locking washers are easier to remove. Thread locker is harder to disassemble but stronger in many cases.
What happens if I overtighten the washer?
You may crush it or reduce its spring effect. Always follow torque guidelines.
Final Thoughts
Locking washers may seem small, but they are essential in construction, mechanics, and safety. The right washer keeps bolts tight, machines running, and people safe.
Always choose the correct washer. Install it carefully. Replace it when needed. Small details can prevent big failures.
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Read More:
How to Use a Lock Washer With a Flat Washer
How to Remove Lock Washer on Dolly Wheels