POWER SCREW
Trapezoidal thread
Tr8 x P2
Tr10 x P2
Tr12 x P3
Tr16 x P4
Tr20 x P4
Tr24 x P5
Tr28 x P5
(Tr30 x P6)
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
Number of thread starts
1
2
3
4
Yield strength screw
MPa
Axial load
10
3
N
Stroke length
10
-3
m
Nut length
10
-3
m
Specific wear rate
10
-15
m
2
/N
Ratio of wear depth / 0.5P
Coefficient of friction
pitch P
10
-3
m
pitch diameter d
2
=d-0.5P
10
-3
m
root diameter d
3
=d-2h
3
10
-3
m
thread height H
1
=0.5P
10
-3
m
tensile stress area A
t
= π/4 d
3
3
10
-6
m
2
tensile stress σ
t
= F/A
t
MPa
torsional stress τ = T/W
p
; W
p
= π/16 d
3
3
MPa
equivalent stress σ
e
= (σ
m
2
+ 3τ
2
)
½
MPa
safety factor S
v
= R
p0.2
/ σ
e
>1
thread support area A
1
10
-6
m
2
total tightening torque T+
Nm
loaded unscrew torque T-
Nm
screw efficiency
%
contact pressure p thread
MPa
total sliding distance s=h/(k p)
10
3
m
sliding distance single move s
1
=π d
2
L
stroke
/ P
m
number of moves L
n
=s/s
1
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