A buttress thread, as shown in Fig.
17.1 (c), is used when large forces act along the screw axis in
one direction only. This thread combines the higher efficiency
of square thread and the ease of cutting and the adaptability to
a split nut of acme thread. It is stronger than other threads because of greater thickness at the base of
the thread. The buttress thread has limited use for power transmission. It is employed as the thread for
light jack screws and vices.