T-59
Table 7-1 presents equations for a profile shifted screw gear pair. When the normal
coefficients of profile shift xn1 = xn2 =0, the equations and calculations are the same as for
standard gears.
Table 7-1 The Equations for a Screw Gear Pair on Nonparallel and
Nonintersecting Axes in the Normal System
3
20°
20° 30°
15 (R) 24 (L)
18.0773 36.9504
21.1728° 22.7959°
0.4 0.2
0.0228415
22.9338°
24.2404° 26.0386°
0.55977
67.1925
47.8880 83.1384
44.6553 76.6445
49.1155 85.2695
20.4706° 30.6319°
51.1025°
4.0793 3.4793
6.6293
56.0466 90.0970
42.7880 76.8384
Normal Module
Normal Pressure Angle
Helix Angle
Number of Teeth & Helical Hand
Number of Teeth of an
Equivalent Spur Gear
Radial Pressure Angle
Normal Coefficient of Profile Shift
Involute Function awn
Normal Working Pressure Angle
Radial Working Pressure Angle
Center Distance Increment Factor
Center Distance
Pitch Diameter
Base Diameter
Working Pitch Diameter
Working Helix Angle
Shaft Angle
Addendum
Whole Depth
Outside Diameter
Root Diameter
Example
Pinion Gear
mn
an
b
z1, z2
zv
at
xn
invawn
awn
awt
y
ax
d
db
dw1
dw2
bw
S
ha1
ha2
h
da
df
z
–––––
cos3b
tanan
tan–1(––––––)
cosb
xn1 + xn2
2tanan(––––––––) + invan
zv1 + zv2
Find from Involute Function Table
tanawn
tan–1(–––––––)
cosb
1 cosan
–– (zv1 + zv2)(––––––– – 1)
2 cosawn
z1 z2
(––––––– + ––––––– + y)mn
2cosb1 2cosb2
zmn
–––––
cosb
d cosat
d1
2ax –––––––
d1 + d2
d2
2ax –––––––
d1 + d2
dw
tan–1(––– tanb
)
d
bw1 + bw2 or bw1 – bw2
(1 + y – xn2)mn
(1 + y – xn1)mn
[2.25 + y – (xn1 + xn2)]mn
d + 2ha
da – 2h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Item
Symbol
Formula
No.
