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The standard designation for a UTS thread is a number indicating the nominal (major) diameter of the thread, followed by the pitch measured in threads per inch.For diameters smaller than 1 / 4 inch, the diameter is indicated by an integer number defined in the standard; for all other diameters, the inch figure is given.
Unified Miniature Screw Threads: V Thread Form: 0.60 UNM ANSI/ASME B1.11-1958 (R2016) Microscope Objective Thread: V Thread Form ASME B1.13M-2005 (R2015) Metric Screw Threads: M Profile: V Thread Form ASME B1.15-1995 (R2003) Unified Inch Screw Threads (UNJ Thread Form) V Thread Form ASME B1.20.1-2013: Pipe Threads, General Purpose (Inch) Pipe ...
A perfectly sharp 60° V-thread will have a depth of thread ("height" from root to crest) equal to 0.866 of the pitch. This fact is intrinsic to the geometry of an equilateral triangle — a direct result of the basic trigonometric functions. It is independent of measurement units (inch vs mm). However, UTS and ISO threads are not sharp threads.
The single-point cutting tools or taps and dies used to cut the thread cannot have efficient rake and relief angles (because of the square form), which makes the cutting slow and difficult. Square threads also cannot carry as much load as a trapezoidal thread, because the root of the square thread is smaller.
The thread depth is 0.54125 × pitch. The outermost 1 ⁄ 8 and the innermost 1 ⁄ 4 of the height H of the V-shape are cut off from the profile. The relationship between the height H and the pitch P is found using the following equation where θ is half the included angle of the thread, in this case 30°: [ 3 ]
Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired. People frequently use a chart such as this to determine the proper tap drill for a certain thread size or the proper tap for an existing hole.
The thread form follows the British Standard Whitworth standard: Symmetrical V-thread in which the angle between the flanks is 55° (measured in an axial plane) One-sixth of this sharp V is truncated at the top and the bottom; The threads are rounded equally at crests and roots by circular arcs ending tangentially with the flanks where r ≈ 0 ...
Final tapping is achieved with single tap. ... US tap and drill bit size and reference chart [7] ... Solid dies cut a nominal thread form and depth, whose accuracy is ...