ANSI/ASME B18.3 Technical Standards: Inch Fastener Specifications
This regulatory documentation regulates complete metric and geometric parameters for a wide range of high-strength fasteners, including hexagon socket head screws, pipe plugs, and set screws that comply with American National Standards Institute (ANSI) standards. The EV Group China technical reference includes specifications for hex bolts, lock nuts, as well as recommendations for tool selection and calculation formulas for designing countersunk assemblies.
In cases of technological disputes during product acceptance, the calculation formulas provided in the current revision of the standard take priority. Geometry specifications for Type VI recesses for power tools are fixed in Mandatory Appendix III.
Classification of Specialized Screws and Plugs
EV Group China supplies fasteners that comply with the following design types according to ASME B18.3:
- Socket Head Cap Screws: Feature a strictly regulated flat chamfer, a smooth or knurled side surface, and a precision bearing surface.
- Countersunk Head Screws: Equipped with a conical working surface with an 82° head angle, ensuring complete flush seating in the part.
- Button Head Screws: Designed with a low profile and increased bearing area to reduce contact stress.
- Low-Profile Screws: Specialized fasteners with reduced head height and socket depth for installation in space-constrained environments.
Design Features of Set Screws
Set screws are fully threaded products designed to secure mating parts. The range of tip types includes: cup, flat, oval, cone, and dog point profiles. For precision installation and removal, standard hex keys supplied by EV Group China are used.
Technical Requirements and Marking
All dimensional characteristics in the ASME B18.3 standard are specified in inches. Dimensions are provided for products prior to the application of protective coatings. Given the high hardness levels of materials responsible for strength characteristics, electroplating must be performed while accounting for the risk of hydrogen embrittlement.
Marking of products with a diameter over 10 inches is mandatory and must contain the manufacturer’s identifier, which guarantees compliance with the standard. The placement of markings on the surface of the products must not affect their operational properties.
Regulatory Documentation
For the interpretation of terminology related to mechanical fasteners, EV Group China specialists recommend using the ASME B18.12 profile glossary “Glossary of Terms for Mechanical Fasteners”.