T-79
approximated by the following equation:
Amount of Crowning
px – px' d1
= k ––––––– –––
(9-5)
px' 2
where:
d1 =
Pitch diameter of worm
k
=
Factor from Table 9-5 and
Figure 9-10 (on following page)
px =
Axial pitch after change
px' =
Axial pitch before change
Table 9-5 The Value of Factor (k)
Fig. 9-9 Position A is the Point of
Determinig Crowning Amount
An example of calculating worm crowning is shown in Table 9-6.
Table 9-6 The Calculation of Worm Crowning
* It should be determined by considering the size of tooth contact surface.
Formula
mx'
an'
zw
d1
g'
ax'
px'
L'
CR'
k
tx
ax
mx
g
an
L
ax
k
14.5°
0.55
17.5°
0.46
20°
0.41
22.5°
0.375
After Crowning
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
3
20°
2
44.000
7.765166°
20.170236°
9.424778
18.849556
0.04
0.41
9.466573
20.847973°
3.013304
7.799179°
20.671494°
18.933146
mx' zw
tan–1(–––––)
d1
tanan'
tan–1(––––––)
cosg'
pmx'
pmx' zv
*
Find from Table 9-5
2CR
tx' (––––– + 1)
kd1
px'
cos–1(––– cosax'
)
px
px
–––
p
mx zw
tan–1(–––––)
d1
tan–1(tanax cosg )
pmx zw
Axial Module
Normal Pressure Angle
Number of Threads of Worm
Pitch Diameter of Worm
Lead Angle
Axial Pressure Angle
Axial Pitch
Lead
Amount of Crowning
Factor (k)
Axial Pitch
Axial Pressure Angle
Axial Module
Lead Angle
Normal Pressure Angle
Lead
Example
No.
Item
Symbol
Before Crowning
d1
30°
A
