Calculation of torque and contact load
   n=  F=kN   =     H'=
Calculation of service live
h'=  Llift=mm   k=10-15 m2/N
 pitch P mm
 pitch diameter d2=d-0.5P mm
 root diameter d3=d-2h3 mm
 tensile stress area As = π/4 d33 mm2
 thread depth H1=0.5P mm
 tensile stess σm = F/A3 MPa
 torsion stress τ = T/Wp ;  Wp= π/16 d3 MPa
 equivalent stress σe = (σm2 + 3τ2) MPa
 ultimate tensile strength Rm  MPa
 0.2% yielding strength Rp0.2 MPa
 safety factor Sv = Rp0.2 / σe >1
 friction torque forward drive T+ Nm
 friction torque backdrive T- Nm
 screw efficiency %
 contact pressure p thread MPa
 total sliding distance s=h/(k p) km
 sliding distance one cycle si=2(π d2 Llift / P) m
 number of cycles Ln=s/si