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406 WORMS AND WORM GEARS.
TABLE No. 53.—Showing How to Gear Lathes when Cut=
ting Worms of the Pitches Given in Table No. 52
.
(Single Thread)
z
a
u
H „5
<
w
LEADING SCREW OF LATHE.
3 3 4 5 6 10
^ K
H u Threac Threads Threads Threads Threads Threads
K U
< Z
5
u
C-1 per inch. per rich. per inch. per inch. per inch. per inch.
*£ i-T
*s C
5 £
u
*£ u
* S
u !> *<
T3 (U V i) *o <U v <u T3 <U V V T3 u <u s T3 4)
U £ 3 bo s«l 3 bfl
o &» 3 M o w 3 M u "" 3 buo
y M 5 M h bD
CO CO CO co CO CO CO CO CO GO CO in
2 Vc 160 40
l
3
/f y7 140 40
l
1
^ % 120 40
1^ % 100 40 120 32
1 i 80 40 96 32
% IK 60 40 72 32 120 40
% i% 50 40 60 32 100 40
X
2/5
2 40 40 48 32 80 40 100 40
2^ 40 50 48 40 64 40 80 40
2/
T
B 40 60 48 48 64 48! 60 36 48 24
3%
4
40 70 48 56 64 56 60 42 48 28
40 80 24 32 40 40 50 40 48 32
4^ 40 90 24 36 32 36 j
40 36 48 36
^ 5 20 50 24 40 32 40 40 40 48 40 60 30
v6 6 20 60 24 48 32 48 40 48 48 48 60 36
1
TO
<S 20 80 24 64 24 48 30 48 48 64 60 48
10 20 100 24 80 24 60 24 48 24 40 50 50
Reduction of Speed by Worm Gearing.
In a single-threaded worm screw one revolution of the worm
moves the gear one tooth ; in a double-threaded worm screw one
revolution of the worm moves the gear twO teeth, and in a triple-
threaded worm screw one revolution of the worm moves the
gear three teeth. A great deal of work is lost in friction by-
using worm gearing, frequently from 50 to 75 per cent., some of
which could be saved by using a ball bearing to take the end
thrust of the worm. The efficiency is also increased by using a
worm of double, triple or quadruple thread, because this in-
creases the angle of the teeth in the wheel and the efficiency of
worm gears and spiral gears is increased by increasing the angle
until it reaches 40 to 45 degrees; when over 60 degrees it rap-
idly falls off again.
Calculating the Size of Worm Gears.
Example.
Find dimensions of a worm gear having 68 teeth, % inch
pitch, cut teeth. Make the pitch diameter of the triple-threaded
worm six times the pitch of the worm. Use Table No. 52.
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