page_title: Unified Thread Standard
section_title: Basic profile
hierarchical_section_title: Unified Thread Standard / Basic profile
context_page_description: The Unified Thread Standard defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, but the characteristic dimensions of each UTS thread were chosen as an inch fraction rather than a millimeter value. The UTS is currently controlled by ASME/ANSI in the United States.
context_section_description: Each thread in the series is characterized by its major diameter Dₘₐⱼ and its pitch, P. UTS threads consist of a symmetric V-shaped thread. In the plane of the thread axis,  the flanks of the V have an angle of 60° to each other. The outermost ​¹⁄₈ and the innermost ​¹⁄₄ of the height H of the V-shape are cut off from the profile.
  The pitch P is the distance between thread peaks. For UTS threads, which are single-start threads, it is equal to the lead, the axial distance that the screw advances during a 360° rotation. UTS threads do not usually use the pitch parameter; instead a parameter known as threads per inch (TPI) is used, which is the reciprocal of the pitch.
  The relationship between the height H and the pitch P is found using the following equation where  is half the included angle of the thread, in this case 30 degrees:
  or
  In an external (male) thread (e.g., on a bolt), the major diameter Dₘₐⱼ and the minor diameter Dₘᵢₙ define maximum dimensions of the thread. This means that the external thread must end flat at Dₘₐⱼ, but can be rounded out below the minor diameter Dₘᵢₙ. Conversely, in an internal (female) thread (e.g., in a nut), the major and minor diameters are minimum dimensions, therefore the thread profile must end flat at Dₘᵢₙ but may be rounded out beyond Dₘₐⱼ.
  The minor diameter Dₘᵢₙ and effective pitch diameter Dₚ are derived from the major diameter and pitch as
caption: The basic profile of all UTS threads is the same as that of all ISO metric screw threads. Only the commonly used values for Dmaj and P differ between the two standards.