Full resolution (JPEG) - On this page / på denna sida - Screws - To calculate the change gear wihen cutting metric screws by an English lead-screw
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SCREWS. 437
Example
To gear a lathe in order to cut a metric standard screw
24 millimeters in diameter and of three millimeters pitch, the
lead-screw on the lathe having four threads per inch.
Solution
:
Twenty divided by three gives 6%, therefore gear the lathe
as if it was to cut 6% threads per inch with a common inter-
mediate gear, and throw in the special intermediate gear as
shown in the cut, and the lathe will cut a screw of three milli-
meters pitch. The gearing is easily obtained, thus:
The ratio between the screw gear and the stud gear is as 6% to
4, which is the same as 20 to 12, or, reduced to its lowest terms, 5
to 3. Hence, the gears may have any number of teeth providing
the ratio is 5 to 3 ; for instance, multiplying by 9, 45 and 27
could be used, or, multiplying by 10, 50 and 30 could be used,
etc.
TABLE No. 74 .—How to Gear a Lathe when Cutting Metric Thread,
Using inch-Divided Lead=Screw and Intermediate Gears, as
Shown in Fig.
3
Screw
to
be
Cut.
(.Pitch
in
Milli-
meters).
LEAD-SCREW ON LATHE.
2
Threads per
Inch.
3
Threads per
Inch.
4
Threads per
Inch.
1
5
;
Threads
per Inch.
6
Threads
per Inch.
10
Threads
per Inch.
5 w>
CO
V V
— OX)
CO CO
3 M
CO CO in
!20
CO
80
_ re
3 M
24
CO
80
~ V
3 W)
CO
20
£ a)
40 I
1 . , 24 120
1.5 24 80 30 80 36 80 30 40
2 20* 100 24 80 24 60 30 60 24 40 40 40
2.5 20 80 1
24 64 :
24 48 30 48 30 40 50 40
3 24 80 27 60 j
24 40 30 40 36 40 60 40
3.5 28 80 21 40 28 40 35 40 42 40 70 40
4 32 80 24 40 32 40 40 40 48 40 80 40
4.5 27 60 27 40 36 40 45 40 54 40
5 30 60
;
30 40 40 40 50 40 60 40
.
5.5 33 60 33 40 44 40 55 40 66 40
6 36 60 j
36 40 48 40 60 40 72 40
6.5 39 60 39 40 52 40 65 40
7 28 40 42 40 56 40 70 40
7.5 30 40 !
45 40 I
60 40
8 32 40 !
48 40 !
64 40
8.5 34 40 51 40 j
9 36 40 54 40
9.5 38 40 57 40
10 40 40 60 40
10.5 42 40
11 44 40
11.5 46 40
12 48 40
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