the elements of screws and shows that diameters, pitch, flank angles,
and thread form have to be controlled. There can be interaction between the errors thus affecting the assembly and fit of screws. Although these notes are not intended to describe the manufacture of screws, it is important to stress attention to certain requirements. The thread cutting device, i.e. form grinding wheel, tap, die, or lathe tool, must provide an accurate form; a form tool must be presented square to the axis of the screw blank and with its form in a diametral section; the pitch must be under precise control.