ASME/ANSI B18.21.1 Helical Spring Lock Washers
Washers feature a helical split-ring construction that provides an elastic spring action when compressed beneath a bolt head or nut. The washer’s angled ends create a spring-loaded interface within the joint and provide resistance to fastener rotation after installation.
The standard covers several configurations, including Regular, Heavy, Extra Duty, and High-Collar types, allowing the washer to be selected according to the available space, fastener size, and required joint characteristics. The helical profile also distinguishes these washers from flat washers, which primarily provide a bearing surface without the same spring configuration. For reliable selection, the washer type, nominal fastener size, material, hardness, and surface finish should be considered together with the joint design. Carbon steel and stainless steel versions can be specified according to the applicable requirements of ASME/ANSI B18.21.1.
Specification:
ASME/ANSI B18.21.1 covers the dimensional and physical requirements for Helical Spring-Lock Washers in inch-series sizes. The standard includes different washer configurations to accommodate different fastening requirements, while material and hardness requirements vary according to the selected material.
Material & Hardness
Carbon and Alloy Steel: Carbon and alloy steel Helical Spring-Lock Washers are specified at 38–46 HRC (372–458 HV) according to the applicable requirements of ASME/ANSI B18.21.1.
Stainless Steel: Stainless steel versions have different hardness requirements depending on washer size. For sizes up to 5/8”, the specified range is 35–43 HRC (345–423 HV); for sizes above 5/8”, the range is 32–43 HRC (318–423 HV).
Washer Types
Regular: General-purpose configuration for standard fastening applications.
Heavy: Increased cross-section for applications requiring a more robust spring-lock washer.
Extra Duty: Heavier construction for more demanding fastening conditions.
High-Collar: Higher collar configuration for applications where the additional section height is required.
| Item | Specification |
|---|---|
| Standard | ASME/ANSI B18.21.1 |
| Product Type | Helical Spring-Lock Washer |
| Thread System | Inch |
| Size Range | Φ#4-Φ2“ |
| Washer Type | Regular,Heavy,Extra Duty,High-Collar |
| Material | Carbon Steel,Alloy Steel,Stainless Steel |
| Carbon Steel&Alloy Steel Hardness | 38-46HRC/372-458HV |
| Stainless Steel Hardness | 35-43HRC/345-423HV up to 5/8", 32-43HRC/318-423HV Above 5/8" |
| Surface Treatment | Plain,Zinc Plated,Bright Finish |
| Mating Fasteners | Compatible Inch-SERIES Bolt, Screw or Nut |
Dimension Chart of ASME/ANSI B18.21.1 Helical Spring-Lock Washers:
The following dimension chart covers Regular Type Helical Spring Lock Washers in accordance with ASME/ANSI B18.21.1. The table provides the key dimensions needed to match the washer with the corresponding inch-series fastener, including nominal size, inside diameter, outside diameter, and washer thickness. When selecting a Regular Type washer, the nominal size should first be matched with the mating bolt or nut. The inside diameter provides fastener clearance, while the outside diameter and washer thickness determine the available bearing area and overall installation profile.
The dimensions shown are for the Regular Type. Heavy, Extra Duty, and High-Collar configurations have different dimensional requirements and should be specified separately when required.
| Mon | #4 | #5 | #6 | #8 | #10 | #12 | 1/4 | 5/16 | 3/8 | 7/16 | 1/2 | 9/16 | 5/8 | 3/4 | 7/8 | 1 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 1-5/8 | 1-3/4 | 1-7/8 | 2 |
| d max | 0.12 | 0.133 | 0.148 | 0.174 | 0.2 | 0.227 | 0.26 | 0.322 | 0.385 | 0.45 | 0.512 | 0.574 | 0.641 | 0.766 | 0.894 | 1.024 | 1.153 | 1.28 | 1.408 | 1.534 | 1.663 | 1.789 | 1.914 | 2.039 |
| d min | 0.114 | 0.127 | 0.141 | 0.167 | 0.193 | 0.22 | 0.252 | 0.314 | 0.377 | 0.44 | 0.502 | 0.564 | 0.628 | 0.753 | 0.878 | 1.003 | 1.129 | 1.254 | 1.379 | 1.504 | 1.633 | 1.758 | 1.883 | 2.008 |
| h min | 0.025 | 0.031 | 0.031 | 0.04 | 0.047 | 0.056 | 0.062 | 0.078 | 0.094 | 0.109 | 0.125 | 0.141 | 0.156 | 0.188 | 0.219 | 0.25 | 0.281 | 0.312 | 0.344 | 0.375 | 0.389 | 0.389 | 0.422 | 0.422 |
| b min | 0.04 | 0.047 | 0.047 | 0.055 | 0.062 | 0.07 | 0.109 | 0.125 | 0.141 | 0.156 | 0.171 | 0.188 | 0.203 | 0.234 | 0.266 | 0.297 | 0.328 | 0.359 | 0.391 | 0.422 | 0.424 | 0.424 | 0.427 | 0.427 |
- RELATED WASHER LISTS:
- DIN125 Flat Washer
- DIN127 Spring Lock Washer
- F436 Hardened Steel Washers
- DIN9021 Large Washer
- ASME/ANSI B 18.21.1 (USS) Flat Washer
- ASME/ANSI B 18.21.1 (SAE) Flat Washer
- DIN25201 Stainless Steel Double Fold Self-locking Washer
- DIN6797A Stainless Steel External Teeth Lock Washers
- Stainless Steel DIN6797J Internal Teeth Lock Washers
Application of ASME/ANSI B18.21.1 Helical Spring-Lock Washers:
Equipment Mounting
Regular Helical Spring Lock Washers are used beneath nuts and bolt heads on equipment frames, motor mounts, brackets, and mounting assemblies. Their helical split-ring structure provides spring action when compressed, making them suitable where a spring-lock washer is specified within a conventional bolted joint.
Machine Covers and Service Components
They can be used for machine covers, guards, access panels, pump components, and serviceable assemblies that may require periodic removal and reinstallation. The compact washer profile fits beneath standard fastener heads without requiring a large external locking surface.
Fabricated Equipment and General Fastening
Regular Type washers are also used in fabricated frames, supports, machinery components, and general industrial assemblies using inch-series bolts and nuts. Their standardized dimensions and consistent spring configuration make them convenient for conventional fastening systems where a B18.21.1 spring-lock washer is specified.