Thread Types for Screws and Fasteners

Thread Types for Screws and Fasteners

Thread Types for Screws and Fasteners

Thread Type Description Usage
Unified Thread Standard (UTS) Standard thread form used in the United States for screws and nuts. General-purpose, wide range of applications.
Metric Thread Thread form based on the metric system, widely used in Europe and other parts of the world. International standard, precise and reliable.
Unified National Thread (UNC) Coarse thread series used for general applications where high vibration resistance is not required. General-purpose screws, bolts, nuts.
Unified National Fine (UNF) Fine thread series used where higher strength or resistance to stripping is needed. Aerospace, automotive, high-stress applications.
Unified Miniature Thread (UNM) Small-diameter thread series used in precision instruments and small devices. Electronics, medical devices, small machinery.
British Standard Whitworth (BSW) Obsolete thread standard once used in the UK and other Commonwealth countries. Historical applications, restoration projects.
British Standard Fine (BSF) Obsolete fine thread standard once used in the UK and other Commonwealth countries. Historical applications, restoration projects.
Acme Thread Truncated thread form with a 29-degree angle, used in applications requiring high strength and wear resistance. Machine tools, jacks, presses.
Buttress Thread Thread form with one side flat and the other side angled, used for applications requiring high axial load capacity. Lathes, milling machines, vices.
Knuckle Thread Thread form with rounded crests and roots, used for easy assembly and disassembly. Adjustable mechanisms, furniture.