A movement's headline size is a starting point. A case must also accommodate its holder, stem position, dial, hands and clearances. Matching one diameter cannot establish compatibility.
| Published measurement | What it helps describe | What it does not establish |
|---|---|---|
| Movement diameter | The movement body's outside dimension | The complete assembly's case fit |
| Diameter with spacer | The envelope including the specified holder | Whether another holder is interchangeable |
| Movement height | A stated vertical movement dimension | Total height including dial and hands |
| Hand-fitting drawing | Post dimensions and height options | Clearance under a particular crystal |
| Stem drawing | Stem geometry and reference dimensions | Finished crown/stem length in your case |
An example from the maker
TMI lists NH35A at 27.40 mm diameter, 29.36 mm with its dial-holding spacer, and 5.32 mm height. Those are distinct measurements. A case description quoting only one of them leaves questions unanswered. Source: TMI NH35A specification, checked 25 October 2026.
Lignes and millimetres
Movement catalogues may give a nominal size in lignes alongside millimetres. Use the maker's actual drawing dimensions for a build rather than converting a nominal size and assuming it describes every outside feature. Preserve units when recording dimensions; do not confuse millimetres with inches or a hand's mounting diameter with its length.
Make a component worksheet
Write down the exact calibre and variant, the supplier's intended movement for the case, the holder supplied, dial dimensions and feet, hand set, crown and stem reference. Add the source drawing beside each entry. If a dimension is missing, ask the supplier instead of filling it from a similar-looking movement.
The movement lookup puts published dimensions together. The comparison checker explains differences, while leaving unverified clearances and interfaces for you to confirm.
Sources & further reading
- TMI NH35A specification and drawings · Checked 2026-10-25