A watch case is not complete in CAD.
It is complete when it can be machined, assembled, and function as intended.
Prototype machining is where:
- geometry is validated
- tolerances are tested
- design errors become visible
If the design is not manufacturable, it fails at this stage.
From CAD to Machining
CAD defines geometry.
Machining defines reality.
The transition requires:
- toolpath generation
- fixture strategy
- material selection
- tolerance capability
Geometry must be compatible with all of these.
Material Selection
Common prototype materials:
- 316L stainless steel
- aluminium (for early testing)
- brass (for rapid machining)
Material affects:
- machining behaviour
- achievable tolerance
- surface finish
Design must account for material properties.
CNC Machining Constraints
CNC machining imposes limits.
Key constraints:
- minimum tool diameter
- tool reach
- internal corner radius
- setup orientation
If geometry ignores these:
- features cannot be machined
- tolerances cannot be held
Tool Access
Every feature must be reachable.
Critical areas:
- crown tube hole
- lug geometry
- internal case features
- caseback threads
Poor access results in:
- incomplete machining
- compromised geometry
Internal Geometry Challenges
Internal features define function.
These include:
- movement seat
- caseback interface
- crystal seat
- gasket grooves
These are difficult to machine due to:
- limited access
- tight tolerances
Design must prioritise machinability.
Tolerance Capability
Machining has limits.
Typical CNC capability:
- depends on machine, tooling, and process
- varies by feature
Design must align with:
- achievable tolerances
- process variation
If tolerances are tighter than capability:
- parts will not be consistent
Surface Finishing Effects
Finishing changes dimensions.
Processes include:
- polishing
- brushing
- blasting
Effects:
- material removal
- edge rounding
- dimensional variation
Design must allow for finishing.
Thread Machining
Caseback threads require:
- precise geometry
- controlled tolerance
Errors lead to:
- poor engagement
- inconsistent sealing
- wear
Thread design must match machining capability.
Assembly Validation
Prototype machining is not the end.
The case must be assembled.
Validation includes:
- movement fit
- crown alignment
- caseback closure
- crystal fit
- lug functionality
Failures at this stage indicate:
- design issues
- tolerance problems
Iteration
First prototypes are rarely correct.
Common adjustments:
- clearance changes
- tolerance adjustments
- interface refinement
Iteration is part of the process.
Design must be adaptable.
What Goes Wrong
Common prototype failures:
- movement does not fit
- crown tube misalignment
- caseback cannot close
- crystal fit incorrect
- threads inconsistent
- features cannot be machined
These originate from:
- ignoring constraints
- designing nominal geometry only
Designing for Machining
Correct approach:
- consider machining during CAD
- ensure tool access
- define realistic tolerances
- allow for finishing processes
- validate in section
The goal is not theoretical geometry.
It is manufacturable geometry.
Relation to System
Prototype machining validates:
- Watch Movement Dimensions and Case Fit
- Watch Case Tolerances Explained
- Watch Crown and Stem Alignment
- Watch Caseback Design
- Watch Crystal Fit and Gasket Compression
If these are correct, machining succeeds.
If not, failure appears here.
Access
HorologyCAD does not offer custom design services.
The focus is on building movement-led case systems that can be used directly.
Manufacturing-ready CAD systems will be released.
Join the list to get access when available.