Square threads are primarily used in applications where high power transmission efficiency and high load capacity is necessary. They are the most efficient thread form owing to thread flanks that are perpendicular to the thread axis. As a result, radial forces on the mating nuts are eliminated and system wear is reduced.
Square threads are useful in cases where side loading is likely to occur since the perpendicular thread flanks eliminate wedging. In such cases it is necessary to minimize diametrical clearances between opposing threads or independently support the screw and nut to maintain axial alignment.
Modified square threads have a trapezoidal form with 5 degree flank angle. Since the angle is small, transmission efficiency is practically equivalent to a true square thread. They have a higher load capacity than standard square threads and are typically less costly to manufacture.
Mod Square Thread Series