Content .. 36 37 38 39 ..

Technology of watch production - part 38

Cam rotation,

degrees, for

Designation of

operations

26th

Plunge No. 5

• • •

27th

Dwell

. • • . • . •

28th Retract No. 5

• • •

2 9th Approach No. 4

Headstock

and tool

travel

0,230

1 ,175

0,945

30th

Plunge No, 4

•

• •

0.1

0.025

0.125

31st

Dwell

• • • . • • •

32nd Retract No . 4

• •

1 .070

33rd Advance headstock 1 .27

34th

Approach No. 2

0.50

35th

Advance headstock 0.1

36th

Advance No, 2

• •

0,1

37th Advance No, 2

• •

1.45

T o t a l . . . . .

0.46

2.35

2: 1 1.890

0,35

2,14

2,54

1 .50

0,2

0.3

4.35

0,005

0.008

0.005

0.008

180

540

(10)

247"

540

360

247

790 revolutions per piece

Production rate

A =

5000: 790= 6 .4 pieces per minute

Approach drill . . .

Dwell . . . . . . . .

Advance drill .

, ,

0.85

112

Retract drill . . . .

1 4 9

113°

Sheet A-3 (cont'd)

Camshaft posi

tion, degrees

�

216

234

236

239

242

252

254

256

260

263

273

106

218

234

236

239

242

252

254

256

260

263

273

360

360"

106

218

230

Cam marking and manufacture. Cam s are marked in a special device

(Figure 3 3 ). The cam is held on the vertical mandrel of the circular table ( 1 )

of the device .

The c am is center-punched along the outer profile b y the c enter punch ( 2 ),

mounted in the bracket ( 3 ) of the plunger (4 ). The plunger can move in the

radial direction, and the value of its displacement is measured on the s c ale

( 5

). The idle-movement curves are laid out by means of the template ( 6 )

FIGURE

33.

Device for cam layout

C ams are manufactured in three operations . The first operation con

s ists in the drilling of holes along the layout contour and the removal of the

excess metal . The s econd operation is the milling of the cam in a special

m achine with an allowance of 0 . 3 - 0 . 4 m m . The third operation involves

bringing the cam to shape on a special m achine':' .

The c am radii are measured in a device with a built-in indicator . A c tual

ly, the differences between the two radii corresponding to the beginning and

the end of a curve are measured, and not the radii thems el ves . A s this dif

ference is equal to the rise or drop on the cam , it must be very accurate,

any inaccuracy in the m anufacture of the cam p rofile being transferred to

the p ro duct.

The smallest radii on the cam , if extending over considerable angles of

rotation, are reduced by 1 mm relative to their c alculated value, so that the

follower will not touch the cam when pas s ing through the arc of this radius,

its lever being supported on a correspondingly adjusted special stop.

This als o m akes it poss ible to p revent the follower from falling into the

ass emblv slots on the cams for tools Nos 3, 4, 5,

• See illustrated catalogue of Glavchasprom MM and P.

1 50

TOOLS AND ATTACHMENTS

The specified high accuracy of geometrical shap e and high surface -finish

quality are achieved by virtue of the accuracy of the s crew machine itself

and by the us e of high-quality tools and attachments .

Tools and implements used with Swiss - type automatic screw machines

include p rismatic tools with carbide ins e rts , twis t d rills (left-hand ), chase r
dies and taps, slotting cutters , and chucking collets .

Tools . The tools must s atisfy rigid requirements relative to the surface

quality of the cutting edges and the stri ct paralleleity and perpendicularity

of the tool - s hank planes . The dimensions and s hapes of tools Nos

and 2

are given in Table 1 6 .

The dimension C i s specified in the tool order.

TABLE

1 6

Dimensions and shape o f tools Nos

and 2, mm

Section

1111

Section

!Ill

1 0

1 00

1 2

100

1 0

1 6

1 00

The cutting edges of the tools are brought to a class 10 o r 11 surface

finish quality on S- 1 94 m achines using boron carbide p owders and diamond

disks (see C hapter IX) . The tool edges are first ground by boron carbide ·

and then p olished on a diamond disk. The grinding gives the tool edges a

dull surface which influences negatively the chip flow and favors heating of

the tip . The m aximum blunting allowed on edges of journal- turning tools

0 . 0 1 mm, and therefor e the carbide tip must be of fine- grained s truc

ture ( 3 . 5 to 5

grain size ) . Carbide tips a r e m a d e of VK6 - VK8 alloy (tung

s ten- cobalt) and are brazed to the s hank using a c opper s older.

The tool shank has strictly parallel and p e rpendicular edges which en

sure the correct positioning of the tool in the slide. The width of the cut - off

1 5 1

tool is especially important. The chips removed by the cut-off tool in

the manufacture of certain watch parts constitute 1 4 0 to 1 8 0 % of the

part weight. The cut- off tool width must consequently be reduced to a min

imum , but this reduction must not increas e the tool vibrations , as this
would impair the surface quality of the part. Recommended cut- off tool

widths are given in Table 1 7 .

TABLE 17

Cut-off tool widths

Tool width, mm

Bar stock diameter, mm

steel

brass

Up to

0 .7

0.7

2 .1 - 4

0.9

0,8

4.1 - 6

1.1

0.9

6 ,1 - 8

1 ,2

1 .0

8 . 1 - 10

1 .5

1 .2

Collets . The dim ensions and s hape of the collets us ed in the Swiss - type

automatic s crew machines a re given in Table 1 8 . The collets are made of

U8A steel. Requirements relative to the collet include the correct gripping
of the bar or tool and concentricity of the hole with the outer guide surfaces ;

the closing cone and the cylindrical s urface . A ccording to specifications ,

the run- out on thes e surfaces must not exceed 0 . 0 1 mm . Run- out is checked

at a dis tance of 5 - 1 0 mm from the collet grip by m eans of a mandrel held

in the collet.

TABLE 18

Dimensions and shape of collets for Swiss-type automatics, mm

Machine let-

a•

through( max .

bar diameter)

7.5

3 5

4 1

1 5

1 6

1 0

9.5

35.5

1 0

5.5

47.5

1 5

1 9

12.6

9.5

1 8

1 0

1 4.5

1 0.5

1 0

Notes : 1 . Admissible radial run-out for d, 0,010 mm.

2. Dimensions

d. 14• D4,

to be taken from tables.

1 5 2

Content .. 36 37 38 39 ..