Technology of watch production - part 45

The s e rvice life of the finishing cutter is the s ame regardless whethe r

two or three passes are made, s ince the slotting cutter facilitates only the

work of the roughing cutter. The s ervice life of s lotting cutters is lower
than that of fo rmed gear cutte rs . The s ervice life of the finishing cutter

(between regrindings ), when milling wheels and pinions made of Ul OA s teel,
is 7 to 8 hours machining time.

FIGURE

1 5 .

Mandrel with cutters :

1-slotting cutter; 2-gear cutter ( roughing); 3-gear cutter

(finishing).

The milling conditions - the feed and speed - are s elected as a function

of the mechanical properties of the material, the blank dimensions and the

cutter material .

If we take the cutting speed of a cutter made of an alloy tool steel such

as KhVG, Kh, etc . as b eing unity, then the cutting speed for cutters made

of high - speed steels such as R 1 8 will be 1 . 5 , and that of cutters made of

carbon steels such as U 1 2A will be 0 . 9 .

I t i s recommended that alloy-s teel cutters b e us ed for milling brass

wheels and pinions and that high - speed- steel cutters ':' be us ed for milling

wheels and pinions made from U l OA or U 7A V steel .

The cutting edges of the cutter teeth become worn during the milling

process and wear is most s e vere at the tooth point, the specific load there
being much higher than along the lateral surfaces .

The criterium for tooth blunting is the width of the wear land b, given

in Table 5 .

TABLE

Acceptable value of cutter-tooth blunting

Cutter type

Hob

Disk

Material machined

Steel

Ilrass

Steel

Wear b, mm

0.15- 0.25
0.07- 0.1 0

Feeds .

The feed rate is established, as already mentioned, as a function

of the mechanical prope rties of the material , the module and the number of

The method of manufacturing cutters from the

VK6

hard alloy has now been mastered. The service life of

such a cutter is several times longer than that of earlier cutters.

177

teeth on the wheel or pinion. Higher feeds are used in milling bras s than

in milling steel. With an increase in the number of teeth and in the module
the size of the blank increases together with its strength and rigidity, and

therefore higher feeds can be used.

In addition, for a given module the tooth space decreases in size with

an increase in the number of teeth, and the dec reas ed volume of metal re

moved, permits the use of highe r feed rates .

The following formula is us ed to determine the feed:

- =

C5M a . zb

m m /tooth'�,

where

s. =

feed per cutter tooth, mm;

a machinability factor;

number of teeth on the wheel or pinion being milled;

module of the wheel or pinion teeth .

The values o f the factor

and the exponents

and b are given i n Table 6 .

TABLE 6

Values of the factor C5 and the exponents

u�d

factor and exponents

Cutting tool

Material 111achined

Hob cutters

Steel

0 .158

0 .54

0.265

Brass

0 .275

0 .54

0.32

Disk cutters

Stee! Z�12

0 .008

0 .72

1 .5

z >12

0.014

0.55

Brass z .;;: 12

0.0017

0 .72

1 .5

z > 12

0.03

0.55

The cutting speed

is established as a function of the m echanical proper

ties of the metal, the gear module and the feed.

The formula used for the determination of the cutting speed is :

C,Mx

V = --

m /min

•

The values of the factor

Cf)

and of the exponents

and y are given in

Table 7 .

A s a time - saving device, the recommended cutting conditions o f the milling

of wheels and pinions by disk cutters are given in Tables 8, 9, and 1 0 .

The milling time T

for a wheel o r a pinion is determined from the for

mula

T =

where

number of teeth on the wheel;

number of teeth on the form cutter;

number of parts machined simultaneously;

feed per tooth, mm;

•

Standards of the " Orgmashpribor" Institute for gear manufacture . 1954.

1 7 8

( 2 )

cutter speed, rpm;

+ l1 + 12 , = total travel , whe re l is the length of the wheel or

pinion milled (or of s e veral wheels ),

is the approach distance

(see table in Appendix 3

and /2 is the cutter overtravel

( 1 - 1 . 5 mm ).

The value of l1 can be determined from the formula

where

is the dep th of cut and d is the cutter diameter.

TABLE

Values of the factor Cv and the exponents

and

Factor and exponents

Cutting tool

Material machined

c"'

Hob cutters

U7AV steel

13.4

0 .42

0.43

U10A steel

12 .2

0 .42

Brass

1 4 1 . 5

0 . 1 6

Disk cutters

U7A V steel

385

1 .8

0 .38

0.1- 0 .2

M > o .2

4 7 . 6

0 . 5

0 . 3 8

U10A steel

350

1 .8

0 .38

0.1- 0 . 2

M > 0 .2

43.2

0.5

0.38

TABLE

Feed,

Sz ,

in mm/tooth for milling teeth on wheels and pinions made from U7AV,

or U1 OA steel using disk cutters

N umber of teeth

Module, mm

on the wheel or

pinion

0 .1

0 .1 2

0 . 1 4

0 . 1 6

0 .1 8

0 . 2 0

0 .25

0 .0034

0 . 0039

0 . 0 043

0 . 0048

0 . 0052

0 . 0056

0 . 0066

1 0

0 . 0 048

0 . 0055

0 . 0061

0 . 0068

0 . 0073

0 . 008

0 . 0094

1 5

0 . 0062

0 . 0074

0 .0087

0 . 0 1 0

0 . 011

0 .0 1 2

0 . 01 5

2 0

0 . 0073

0 . 0088

0 . 0 1 0

0 . 012

0 . 01 3

0 . 0 1 5

0 . 01 8

3 0

0 . 0 091

0 . 01 1

0 .013

0 . 01 4

0 . 01 6

0 . 0 1 8

0 . 02 3

4 0

0 . 0 1 1

0 . 01 3

0 . 0 1 5

0 . 01 7

0 . 0 1 9

0 . 02 1

0 .026

5 0

0 . 0 1 2

0 . 01 4

0.017

0 . 01 9

0 . 022

0 . 024

0 . 03 0

6 0

0 . 0 1 3

0 . 01 6

0 .018

0 . 02 1

0 . 024

0 . 02 6

0 . 033

0 . 014

0 . 017

0 . 02 0

0 . 02 3

0 . 02 6

0 . 029

0 . 036

0 .01 6

0 . 0 1 9

0 . 022

0 . 026

0 . 02 9

0 . 032

0 . 04 0

1 79

( 3 )

0 .30

0 . 0075

0 . 01 1

0 . 01 9

0 . 022

0 . 02 7

0 . 032

0 . 036

0 . 04 0

0 . 043

0 . 048

TABLE

Cutting speed ,

v ,

in m/min, for milling teeth on wheels and pinions made from

U7A V steel using disk cutters

Feed,

'•

Module,

mm/tooth

0.1

0.12

0.14

0.16

0.18

0.20

0.2S

0.30

0.002

9 1

1 1 9

0.003

50.3

77.3

1 0 1

1 25

159

0 ,004

45.1

69.3

1 1 5

1 43

173

0.005

4 1 .4

63.5

83.7

1 06

1 3 1

160

195

0.006

38.7

1 1 9

145

162

1 78

0,008

53.8

70,5

1 1 0

1 34

150

1 64

0,010

3 1 , 9

49.2

64,4

8 1 .5

1 00

1 22

1 36

1 50

0.0 1 5

27.2

86,6

106

1 1 8

129

0,020

24.5

36,6

49.7

63.5

94.7

1 05

1 1 6

0.025

22,5

34,7

45.6

57,7

7 1 .5

86.5

96.6

1 06

0.030

2 1 . 0

32.3

42.3

53.8

66,5

90.2

0.040

48.3

72.5

80.8

0.050

66.7

74,2

8 1 .4

TABLE

1 0

Cutting speed ,

v ,

i n m/min, for milling teeth o n wheels and pinions made from

Ul OA steel using disk cutters

Feed,

•:

Module,

mm/tooth

0.1

0.12

0.14

0.15

0.18

0.20

0.25

0.30

0.002

53.6

82.5

1 08

0.003

45.8

70.3

1 1 7

1 45

0.004

4 1 ,0

63.0

82.5

1 05

1 30

1 57

0.005

37,6

57.7

1 1 9

1 45

1 61

177

0.006

35.2

52,7

87.5

I C8

1 32

1 47

1 62

0.008

3 1 .7

48,7

8 1

100

1 22

1 35

1 49

0,010

44.5

58.4

I l l

1 24

1 36

0,0 1 5

24.8

38.2

63,5

78.7

107

1 1 7

0.020

22.3

34.3

57.1

7 1

95.5

1 05

0,025

20.5

31 .5

4 1 ,2

52.4

78.5

87.6

96.5

0.030

1 9 . 1

29.4

38,5

48,8

60.5

73.4

0.040

43,8

54.5

73.4

80.8

0,050

60,6

67.5

1 80

Content .. 43 44 45 46 ..