POWER SCREW
Calculation of torque and contact load
Tr8 x P1.5
Tr10 x P2
Tr12 x P3
Tr16 x P4
Tr20 x P4
Tr24 x P5
Tr28 x P5
Tr32 x P6
Tr36 x P6
Tr40 x P7
Tr44 x P7
Tr48 x P8
Tr52 x P8
Tr60 x P9
(Tr65 x P10)
Tr70 x P10
(Tr75 x P10)
Tr80 x P10
(Tr85 x P12)
Tr90 x P12
(Tr95 x P12)
Tr100 x P12
(Tr110 x P12)
Tr120 x P14
n=
1
2
3
F=
kN
µ=
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
St.50
St.60
H'=
Calculation of service live
h'=
0.1
0.2
0.3
0.4
0.5
L
lift
=
mm
k=
10
-15
m
2
/N
pitch P
mm
pitch diameter d
2
=d-0.5P
mm
root diameter d
3
=d-2h
3
mm
tensile stress area A
s
= π/4 d
3
3
mm
2
thread depth H
1
=0.5P
mm
tensile stess σ
m
= F/A
3
MPa
torsion stress τ = T/W
p
; W
p
= π/16 d
3
3
MPa
equivalent stress σ
e
= (σ
m
2
+ 3τ
2
)
½
MPa
ultimate tensile strength R
m
MPa
0.2% yielding strength R
p0.2
MPa
safety factor S
v
= R
p0.2
/ σ
e
>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 s
i
=2(π d
2
L
lift
/ P)
m
number of cycles L
n
=s/s
i
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