T-193
Table 17-34 (Cont.) Allowable Stress Factor for Surface Strength, Sc lim
* NOTE: The value indicates the maximum sliding speed within the limit of the allowable stress
factor, Sc lim. Even when the allowable load is below the allowable stress level, if the
sliding speed exceeds the indicated limit, there is danger of scoring gear surfaces.
17.5.6 Examples of Worm Mesh Strength Calculation
Table 17-35A Worm and Worm Gear Design Details
Table 17-35B Surface Strength Factors and Allowable Force
Sliding Speed Limit
before Scoring
(m/s) *
Material of
Worm Gear
Material of Worm
SC lim
Cast Iron (Perlitic)
Phosphor Bronze Casting and
Forging
Cast Iron but with a higher
hardness than the worm gear
0.63
0.42
2.5
2.5
2
20°
4.08562
2.205
40
80
–––
20
Hobbing
12.5 mm
37.5
Al BC2
–––
–––
No.
Item
Symbol
Unit
Worm
Worm Gear
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Axial Module
Normal Pressure Angle
No. of Threads, No. of Teeth
Pitch Diameter
Lead Angle
Diameter Factor
Tooth Width
Manufacturing Method
Surface Roughness
Revolutions per Minute
Sliding Speed
Material
Heat Treatment
Surface Hardness
mx
an
zw , z2
d
g
Q
b
n
vs
mm
degree
mm
degree
mm
rpm
m/s
1
28
14
( )
Grinding
3.2 mm
1500
S45C
Induction Hardening
HS 63 … 68
No.
Item
Symbol
Unit
Worm Gear
1
2
3
4
5
6
7
8
9
10
11
Axial Module
Worm Gear Pitch Diameter
Zone Factor
Sliding Speed Factor
Rotating Speed Factor
Lubricant Factor
Lubrication Factor
Surface Roughness Factor
Contact Factor
Allowable Stress Factor
Allowable Tangential Force
mx
d2
Z
Kv
Kn
ZL
ZM
ZR
KC
SC lim
Ft lim
mm
kgf
2
80
1.5157
0.49
0.66
1.0
1.0
1.0
1.0
0.67
83.5
