Technology of watch production - part 93
C h a p t e r X
ASSEMBLY A ND ADJUSTMENT OF WA TCHES
A s sembly is the last stage in the production process and the assembled
watches must satisfy b oth the All -Union Government Standards and the de
partmental specifications .
The sequence of assembly operations and the m eans and m ethods for per
forming each operation are established in advance , as was the case with the
machining proces s , and the p rocess design must specify which parts reach
the assembly shop as separate units and which as subass emblie s .
A s s embly-process design i s based o n the part drawings and specifications
and on the plant data available .
A high assembly rate i s attained b y using special equipment and fixtures
and interchangeable parts and subass emblie s . Fixed time-rate ass embly
line work is possible only if the parts are completely interchangeable .
I n t e r c h a n g e a b i
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i t y means that any part or subassembly can be
replaced without additional processing while maintaining the operational re
quirements of a given subassembly o r mechanism .
Interchangeability does not, however, exclude additional adjustment of
the parts during their assembly (adjustment is the positioning of matched
parts in a manner which ensures their c orrect functioning in the movement ) .
The u s e o f a regulator within the watch thus allows the watch rate t o b e ad
justed within certain limits without altering the dimensions of the balance
and hairspring.
Interchangeability of parts eliminates fitting time and makes it pos s ible
to carry out the operations at a fixed rate and to employ semiskilled workers .
Interchangeability is als o necessary to allow subsequent repairs . It is
much easier to replace a b roken part by an identical new part than to repair
the broken part. The identical new part will, as a rule, give better per
formance, especially when parts such as the balance with staff and hair
spring, or the pallet lever with guard pin, are replaced.
Interchangeability of parts and subassemblies is achieved by accurate
mechanical working and heat treatment. Interchangeability is class ified as
geometrical or physical . Two mainsprings may be interchangeable geo
metrically (or identical dimensions ) but still differ in their torque, as an
incorrect heat treatment can lead to a lower torque . These springs will
not, therefore, be physically interchangeable .
Dimensional calculations , which give the actual clearances or inter
ferences (negative allowances ) to be anticipated in assemblie s , make it pos
s ible to check whether the planned production process ensures geometrical
interchangeability, and whethe r the movement components will interact
correctly. A ny necessary alterations are introduced on the basis of the
results of thes e calculations .
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