ASME/ANSI B18.21.1 External Tooth Lock Washers
ASME/ANSI B18.21.1 External Tooth Lock Washers are designed with teeth extending outward from the washer perimeter to create a mechanical gripping interface beneath a bolt head or nut. During tightening, the teeth engage with the mating surfaces, helping resist relative rotation between the fastener and the bearing surface.Unlike an internal-tooth washer, whose teeth extend into the area around the fastener hole, the external-tooth design places the locking teeth around the outside diameter. This makes the washer particularly useful when the available bearing surface provides sufficient area for the teeth to engage.
For proper performance, the washer should be selected according to the mating fastener size, inside diameter, outside diameter, thickness, and available bearing surface. Material, hardness, and surface treatment should also be considered when the joint is exposed to vibration, corrosion, painted surfaces, or repeated assembly. A tooth lock washer is not simply a substitute for any washer. Its effectiveness depends on tooth engagement, joint preload, surface hardness, and the design of the mating surfaces.
Specification:
ASME/ANSI B18.21.1 covers the dimensional and physical requirements for tooth lock washers. Our External Tooth Lock Washers are available from #3 to 1” for inch-series fastening applications. For carbon steel versions, the standard specifies a hardness range of 40–50 HRC (approximately 392–513 HV) for tooth lock washers. Stainless steel options can be supplied in applicable grades and hardness conditions according to the requirements of the standard.
| Item | Specification |
|---|---|
| Standard | ASME/ANSI B18.21.1 |
| Product Type | External Tooth Lock Washer |
| Washer Design | External Radial Teeth |
| Tooth Location | Outer Perimeter |
| Thread System | Inch |
| Inner Diamter | #3-1“ |
| Material | Carbon Steel, Alloy Steel, Stainless Steel |
| Surface Treatment | Zinc Plated/Bright Pickling |
| Carbon Steel Hardness | 40-50HRC/392-513HV |
| Stainless Steel301-305 | ≥88HRB Annealed/20-45 HRC Hardened |
Dimension Chart of ASME/ANSI B18.21.1 External Tooth Lock Washers:
The dimension chart of ASME/ANSI B18.21.1 External Teeth Lock Washers provides detailed information about key specifications, including inside diameter, outside diameter, thickness, and tooth dimensions. Manufactured according to the ASME/ANSI B18.21.1 standard, these washers are designed with external teeth extending beyond the outer edge to engage with the bearing surface of the fastener assembly, providing effective resistance against loosening caused by vibration and movement.
| Mon | #6 | #8 | #10 | #12 | 1/4 | 5/16 | 3/8 | 7/16 | 1/2 | 9/16 | 5/8 |
| d max | 0.15 | 0.176 | 0.204 | 0.231 | 0.267 | 0.332 | 0.398 | 0.464 | 0.53 | 0.596 | 0.663 |
| d min | 0.141 | 0.168 | 0.195 | 0.221 | 0.256 | 0.32 | 0.384 | 0.448 | 0.513 | 0.576 | 0.641 |
| dc max | 0.32 | 0.381 | 0.41 | 0.475 | 0.51 | 0.61 | 0.694 | 0.76 | 0.9 | 0.985 | 1.07 |
| dc min | 0.305 | 0.365 | 0.395 | 0.46 | 0.494 | 0.588 | 0.67 | 0.74 | 0.88 | 0.96 | 1.045 |
| h max | 0.022 | 0.023 | 0.024 | 0.027 | 0.028 | 0.034 | 0.04 | 0.04 | 0.045 | 0.045 | 0.05 |
| h min | 0.016 | 0.018 | 0.018 | 0.02 | 0.023 | 0.028 | 0.032 | 0.032 | 0.037 | 0.037 | 0.042 |
ASME/ANSI B18.21.1 Internal Teeth Lock Washers
ASME/ANSI B18.21.1 External Teeth Lock Washers
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Application of ASME/ANSI B18.21.1 External Tooth Lock Washers:
ASME/ANSI B18.21.1 External Teeth Lock Washers are designed for fastening applications where preventing loosening and maintaining connection stability are important. Their external teeth create strong engagement with the contact surface, improving resistance against vibration and movement while helping maintain the reliability of bolted assemblies.
| Application | Details |
|---|---|
| Automotive Industry | ASME/ANSI B18.21.1 External Teeth Lock Washers are widely used in automotive assemblies where fastening reliability is essential. They help secure bolts and screws in components exposed to engine vibration, road impact, and continuous movement, such as engine parts, chassis systems, electrical components, and interior assemblies. |
| Machinery Manufacturing Industry | In industrial machinery, production equipment, and mechanical devices, external teeth lock washers provide additional locking force for threaded connections. Their outward-facing teeth grip the bearing surface firmly, helping prevent fasteners from loosening during long-term operation under vibration or repeated loading conditions. |
| Electrical and Electronic Equipment Industry | These washers are commonly applied in electrical cabinets, motors, control systems, and electronic equipment. They help maintain stable fastening connections while reducing the risk of loosening caused by equipment vibration, ensuring reliable operation of electrical systems. |
| Automation and Robotics Industry | In automated production lines, robotic equipment, and precision machinery, ASME/ANSI B18.21.1 External Teeth Lock Washers are used to improve connection stability in moving assemblies. Their compact design and reliable locking performance make them suitable for applications requiring secure fastening in limited installation spaces. |
| Construction and Engineering Equipment Industry | External teeth lock washers are used in construction machinery, engineering equipment, and structural assemblies where bolts are exposed to dynamic loads and environmental changes. They help maintain fastening integrity and improve the overall durability of assembled structures. |
| Transportation Industry | In railway equipment, trucks, marine equipment, and other transportation systems, these washers provide effective anti-loosening performance for critical fastening points. Stainless steel versions are especially suitable for applications requiring corrosion resistance and long-term reliability. |