Learn about new technologies! 
The factional torque for square thread at the mean radius r while raising load W is given by
T = W.r tan(φ - α)
T = W.r tan(φ + α)
T = W.r tanα
T = W.r tanφ
T = W.r tan(φ - α)
T = W.r tan(φ + α)
T = W.r tanα
T = W.r tanφ