Technology of watch production - part 22

Figure 4 0 , c shows an indentation with a cylindrical portion. The drill

is initially guided by the cylindrical part, and later by the conical part.
This type of center-pointing is recommended for diam eters above

mm and

in parts 3 mm or more thick.

Figure 40, d shows the position of the drill in an indentation with an angle

larger than the drill -point angle. In this case the drill contacts the crater
with its point, and not with the cutting edges as in the preceding cases . The

accuracy of drilled holes is lower with this type of indentation .

The required p ointing depth is a function of the diameter of the hole to

be drilled.

The points mus t protrude above the die by 0 . 3 - 0 . 5 mm more than their

actual desired penetration, in order to ensure that a clearance will always

e xist between the work and the die fac e , preventing dan
gerous "dead" impacting of the

pres s .

Hole diameters are divided into s everal groups in order

to reduce the variety of pointing-punch size s . Thus, only

three pointing-punch sizes ( 1 , 1 . 8 , and 2 . 5 mm ) are used in

drilling holes of diameters 0 . 5 0, 0 . 6 , 0 . 7 5 , 1 . 1 0 , 1 . 2 0, 1 .4 0 ,

1 . 8 0 , 2 . 0 and 2 , 2 0 mm .

If the distance between centers for two holes is smaller

than the s um of the radii of the pointing punches , flats are

machined on both punches (Figure 4 1 ).

The design of pointing dies mus t allow for easy replace

ment of the pointing punche s . F re quent replacement is

necessary as metal adheres to the punch point and sp reads

FIG URE

41.

Mount-

over the cone s urface, dis torting the s hape of the indenta-

iug of the pointing

tions .

punches for small dis-

tances

tween centers

The accuracy of the center punching must not be affected

by the frequent dism antling of the die s et and by the removal

and replacement of the p ointing punches themselve s .

Repeated grindings o f the pointing-punch tips reduces their total length

and it eventually becomes insufficent fo r forming the indentations . In s uch

cases either the pointing punches are replaced o r the die-plate thickness is
reduced.

The most widely used pointing-die design is shown in Figure 4 2 .

The hardened - s teel die plate ( 3 ) is mounted o n the lower shoe of the die

set and in it are fixed the pointing punches (8 ). The die plate is connected

to the disk ( 6 ) by screws ( 7 ) and the pin ( 9 ) . The s upporting pins ( 1 0 ), o n

which the  p art i s  placed,  are mounted i n  the  disk.  The  knock-out pins  (5 ),
actuated by the  knock- out bar  (4 ),  pass through the  disk (6 ) .   The nesting
pins  (2 ),  which locate  the  part in the  horizontal plane  are  mounted on the

die plate.

The flat- faced punch ( 1 ), provided with clearance holes to take the nest

ing pins (2 ) is mounted in the upper s ho e . When the punch i s lowered, the

part des cends together with the s upporting pins and is pressed against the

pointing punches . When the punch recedes upward, the s upporting pins ,

being spring-loaded, lift the part off the pointing punches . The part is

remo ved from the nesting pins by a p edal, the knock- out bar (4 ), and the

knock- out pins ( 5 ).

It might happen that the longest punches are concentrated on one side

of the die, and the sho rtest punches on the other. The supporting pieces

p revent dis tortion of the part in s uch cases .

In watch movements the bridges are mounted above plates and the cor

responding holes have the s ame coordinates in both parts . A single die

can therefore be designed for p ointing the holes first in the plate and then,

simultaneously, in the corresponding bridges . This increases the accuracy

of hole  location  in m ating parts ,  and als o  reduces  the  number of dies  re
quired,  althoug s uch  a  combination die is  more complex than  each of a  s et
of separate  die s .

FIGURE

42 .

Pointing die

Only through - holes can be pointed on bridges by means of s uch a die .

Blind holes necessitate a s eparate d i e for each bridge. The accuracy of

hole location for pointed holes is 0 . 0 3 mm . The positional accuracy obtain

able by the use of drilling jigs is 0. 05 m m .

The pointing process is very productive and the number of holes pointed

is limited only by the part and pointing-punch dimensions . The usual dies

can point between 2 and 2 5 holes .

The shortcoming of hole location by pointing is that the drill operator,

using a drill of a given diameter, c ould conceivably e rr in his choice of

pointing marks corresponding to the given drill, when faced with a large

number of pointing marks . Perforated templates (holes 0 . 0 5 - 0 . 1 mm larger
than the hole to be drilled ) are used to o vercome this disadvantage. Each

template is designed for holes of only one diamete r .

8 6

Embossing and coining*.

These operations are used in watch production

for obtaining design in relief on the back lid of watches (Figure 43 )

for

producing rais ed figures and symbols on dials (Figure 44 ) and fo r other

si'Tiilar operations .

FIGURE 43. Back lid of a pocket-watch
c ase with e mbossed design

FIGURE

45.

Wristwatch mechanism with

symbols, figures and inscriptions

FIGURE 44 . D i a l 1v ith embossed ( raised)

figures

FIGURE 46 . Stamping

depth of figures and
symbols

•

[Russian terminology  does  not  differentiate  between embossing  and  coining  dies .  As these two  terms  are
frequently confused in  American  usage,  it  might  be  w orthwhile  to  attempt a  working definition of the
difference betlveen the  two :  embossing  dies have  usually  the  same  design  on  the  upper  and  on  the  lower

die, one being the negative of the other, while coining dies generally present different designs on the

upper  and  lower die ,  respectively .  A  special case  of the  embossing-type  of  die  is  the  die  used  to embellish
the w atch  lid shmvn  in Figure 43.  Here one  die  represents  the negative of the  desired  lid surface,  while
the  other  die  is smooth,  serving  only  as  countersupport . ]

Stamping.

Symbols and figures are often stamped on the bridges and

winding wheels of watch movements . Stamping is accompanied by a local

plastic deformation. Stamped ins criptions , figures and s ymbols on the

movement of a "Pobeda " wristwatch are s hown in Figure 4 5 . The approxi

mate s tamping depth is indicated in Figure 4 6 .

SIVAGING

In s waging the blank is completely contained in the die under pressure

from all sides .

The blanks us ed are of a s hape approximating that of the final part,

(cylinders , disks , etc . ). The volum e of the blank is equal to that of the

FIGURE 47 .

Pendant of pocket

watches

a-blank; b- after the first oper

ation; c-after the second swag
ing operation.

final part with a s m all s urplus which is required
to ensure that the die is completely filled . This

s urplus goes into the formation of flash (burrs

at the parting face of the die ) which has to be

removed. The blank for the pendant of pocket

watches is obtained by cold heading from bar stock

and is  s hown  in Figure  47,  a ,   while  Figures  4 7 ,
b  and  c  show the pendant  after the first and s econd
s waging s tages  on a hydraulic pres s .

The blank i s annealed and cleaned after the

heading and after the first s waging operation.

Swaging can be treated as a kind of embossing

or coining, since the nature of thes e processes
is very similar, as are the working pressures

involved (see Table 5 ) .

Metals to b e s waged must b e ductil e . Ductili

ty is characterized by the am ount of deform ation

the metal can endure without fracture. In s wag

ing, the deformation is defined by the relations hip

o r

1 00,

where

the deformation in %;

and

H f

the initial and final heights of the blank and part, respectively.

and

the initial and final cross -sectional areas of the blank and part,

resp ectively.

Embossing, coining and s waging operations require considerable p res

s ures (Table 5

)

The force

required is determined from the formula

P = q · F,

where

q =

the pressure in kg/mm 2 ;

F =

the part s urface (in plane ) in mm2 .

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