5/32″ x 32 TPI carbon Second tap
Thread form
The form of a Whitworth thread is based on a fundamental triangle with an angle of 55° at each peak and valley. The sides are at a flank angle of Θ = 27.5° perpendicular to the axis. Thus, if the thread pitch is p, the height of the fundamental triangle is H = p/(2tanΘ) = 0.96049106p. However, the top and bottom 1⁄6 of each of these triangles is cut off, so the actual depth of thread (the difference between major and minor diameters) is 2⁄3 of that value, or h = p/(3tanΘ) = 0.64032738p. The peaks are further reduced by rounding them with a 2×(90° − Θ) = 180° − 55° = 125° circular arc. This arc has a height of e = Hsin Θ/6 = 0.073917569p (leaving a straight flank depth of h − 2e = 0.49249224p) and a radius of r = e/(1 − sin Θ) = 0.13732908p.
