Section 17 Strength and Durability of Gears - SDP/SI

ELEMENTS OF METRIC GEAR TECHNOLOGY
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17.3.3.D Spiral Angle Factor, Y β
The spiral angle factor is a function of the spiral angle. The value is arbitrarily set
by the following conditions:
β
When 0 ≤ β m
m ≤ 30°, Y β = 1 – –––– ⎫
120 ⎪ ⎬ (17-36)
⎪
When β m ≥ 30°, Y β = 0.75 ⎭
17.3.3.E Cutter Diameter Effect Factor, Y C
This factor of cutter diameter, Y C , can be obtained from Table 17-20 by the value of
tooth flank length, b / cos β m (mm), over cutter diameter. If cutter diameter is not known,
assume Y C = 1.00.
Types of Bevel Gears
Straight Bevel Gears
Spiral and Zerol Bevel Gears
Table 17-20 Cutter Diameter Effect Factor, Y C
∞
1.15
–––
Relative Size of Cutter Diameter
6 Times
Tooth
Width
5 Times
Tooth
Width
4 Times
Tooth
Width
17.3.3.F Life Factor, K L
We can choose a proper life factor, K L , from Table 17-2 similarly to calculating the
bending strength of spur and helical gears.
17.3.3.G Dimension Factor Of Root Bending Stress, K FX
This is a size factor that is a function of the radial module, m. Refer to Table 17-21
for values.
–––
1.00
–––
0.95
Table 17-21 Dimension Factor for Bending Strength, K FX
Radial Module at
Outside Diameter, m
1.5 to 5
above 5 to 7
above 7 to 9
above 9 to 11
above 11 to 13
above 13 to 15
above 15 to 17
above 17 to 19
above 19 to 22
above 22 to 25
Gears Without
Hardened Surface
1.0
0.99
0.98
0.97
0.96
0.94
0.93
0.92
0.90
0.88
–––
0.90
Gears With
Hardened Surface
1.0
0.98
0.96
0.94
0.92
0.90
0.88
0.86
0.83
0.80
Metric
0 10
I
R
T
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
T-177
A