16
Copyright © 2020 Quality Machine Tools, LLC
PM-1440GS v3 2020-10
WORM CUTTING — U.S.
The following table lists
DP
(Diametral Pitch) values for worm-wheels, and the gearbox settings to cut
matching worms. Example: a 16DP worm wheel has a
Circular Pitch
of π ÷ DP = 3.142 ÷ 16 = 0.1963".
This is the distance between a point on one tooth of the worm-wheel and the corresponding point on its
adjacent tooth.
A matching worm has a
Linear Pitch
of the same value. In other words, the "thread pitch" of the worm
is also 0.1963". In the table the setup for this pitch is
HCTY-1
. Compare this with GCTY-1 (U.S. threads
table, preceding page) for a 4 TPI thread, pitch 0.25". Gear set H runs the leadscrew slower (π/4) than G,
so the worm pitch is 0.25 x π/4 = 0.1963".
The following table lists
Module
numbers for metric worm-wheels, and the gearbox settings to cut match-
ing worms. (Module is the inverse of diametral pitch, but with the pitch circle diameter measured in mil
-
limeters instead of inches.) Example: a
Module 1.5
worm-wheel has a
Circular Pitch
of π x 1.5 = 4.712
mm. This is the distance between a point on one tooth of the worm-wheel and the corresponding point
on its adjacent tooth.
A matching worm has a
Linear Pitch
of the same value. In other words, the "thread pitch" of the worm
is also 4.712 mm. In the table the setup for this is
HBRW-6
. Compare this with GBRW-6 (Metric threads
table, preceding page) for a thread of 6 mm pitch. Gear set H runs the leadscrew slower (π/4) than G, so
the worm pitch is 6 x π/4 = 4.712 mm.
1
2
3
4
5
6
7
8
HCTY
16
18
20
44
23
24
26
28
HCSY
32
36
40
44
46
48
52
56
HBY
38
38
38
38
38
38
38
38
HCRY
64
72
80
88
92
96
104
112
1
2
3
4
5
6
7
8
HATW
0.1
0.125
0.15
HASW
0.2
0.225
0.25
0.275
0.2875
0.3
0.325
0.35
HBTW
0.375
HARW
0.4
0.45
0.5
0.55
0.575
0.6
0.65
0.7
HBSW
0.5625
0.625
0.6875
0.75
0.8125
0.875
HBRW
1
1.125
1.25
1.375
1.5
1.625
1.75
SCREW CUTTING — METRIC THREADS
The following table lists thread pitch in mm.
Gear Set F
cuts all
fine
threads from M1 to M18 diameters,
plus all
coarse
threads from M1.6 to M12 diameters, with a
single exception (M5 x 0.8).
Gear Set G
cuts all
coarse
threads from M14 to M68 diam-
eters, plus M5 x 0.8.
1
2
3
4
5
6
7
8
FATW
0.1
0.125
0.15
FASW
0.2
0.225
0.25
0.3
0.35
FARW
0.4
0.45
0.5
0.55
0.6
0.65
0.7
FBSW
0.75
0.875
GASW
0.8
0.9
1.1
1.2
1.3
1.4
FBRW
1
1.25
1.5
1.75
GARW
1.6
1.8
GBSW
2
2.25
2.5
2.75
3
3.25
3.5
GBRW
4
4.5
5
5.5
5.75
6
6.5
7
WORM CUTTING — METRIC
