Definition
Movement to case fit defines how a selected movement is translated into a functional case geometry.
This step establishes the relationship between movement dimensions and the internal case structure required to house it.
It converts movement data into a usable design envelope.
Role Within the System
Movement to case fit is the transition between selection and engineering.
It sits between:
Movement Selection
→ Movement to Case Fit
→ Constraint Definition
At this stage, the movement is fixed and all case geometry begins to derive from it.
Movement as the Reference Geometry
The movement defines the primary dimensions that control case design:
movement diameter
movement height
stem position
dial and hand stack envelope
These parameters establish the boundaries within which the case must be engineered.
No case dimension can be defined independently of these constraints.
Establishing the Case Envelope
The first step in case design is defining the internal envelope required to contain the movement.
This includes:
radial envelope (case diameter relative to movement)
axial envelope (case thickness relative to movement height)
vertical positioning of the movement within the case
This envelope forms the base structure for all further design decisions.
Primary Fit Conditions
Movement to case fit is governed by three primary conditions:
Radial Fit
Defines the relationship between movement diameter and internal case diameter.
This determines:
lateral stability
available clearance for insertion
space for movement securing systems
→ Radial Clearance
Axial Fit
Defines the relationship between movement height and case thickness.
This determines:
crystal clearance
caseback position
internal stack height
→ Axial Clearance
Positional Alignment
Defines the vertical and angular positioning of the movement.
This determines:
stem alignment with crown
dial position relative to crystal
caseback sealing interface
→ Internal Case Geometry & Movement Cavity Sizing
Why This Step Matters
Failure to correctly define movement to case fit results in:
incorrect case proportions
misaligned crown and stem
insufficient internal clearance
interference between components
All downstream errors originate from incorrect initial fit definition.
System Integration
Movement to case fit defines the starting geometry for all constraint pages.
Once established, proceed to:
Radial Clearance
Axial Clearance
Internal Case Geometry & Movement Cavity Sizing
These define the detailed constraints required to produce a valid case design.
Final Statement
Movement to case fit converts a selected movement into a defined case structure.
A valid design must:
derive all internal geometry from movement dimensions
define radial and axial relationships before detailing
maintain alignment between all interfacing components
If movement fit is not correctly defined, the case cannot be engineered.
Next Step
Once the movement has been selected, the next constraint is the internal case geometry that will physically contain and locate it.
Continue to: Internal Case Geometry & Movement Cavity Sizing
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