Use the lift angle published for the movement. If you cannot find it, measure the amplitude against a known angle or report the reading as approximate — but never quote an amplitude without saying which angle produced it.
What lift angle should I use?
issue ISSUE 01checked 2026-09-16responsible Escapement Papers (a named bench, not a person)
What you need The movement's specification, or a service manual; a timing machine or app whose lift angle is settable; a way to note the angle next to every reading.
tape card: the cost of a wrong angle
| Lift angle used | Amplitude reported | True amplitude at 52° |
|---|---|---|
| 52 degrees | 280 | 280, correct |
| 44 degrees | about 310 | 280, overstated by 30 |
| 60 degrees | about 250 | 280, understated by 30 |
| unknown | unusable | not a measurement |
Steps
- Look up the lift angle for the specific movement, not the brand. It is usually in the service manual and often quoted on a technical sheet.
- Set it on the machine before you take any reading, and re-set it when you change movements.
- If the value is unavailable, note that the amplitude is approximate and say which angle you used.
- For a watch with a known-good amplitude, sanity-check the angle: if the reported amplitude is above about 320 degrees at full wind, your angle is probably too small.
- Write the angle next to every amplitude you record, including in your own notes.
Why the number is a property of the movement
| What the lift angle describes | Why it differs between movements |
|---|---|
| The angle the balance turns while it is being impulsed | Fork geometry and roller jewel size |
| The part of the swing the machine cannot see | Pallet depth and banking |
| A fixed number for a given calibre | Adjustments after assembly do not change it |
The arithmetic of being wrong
Amplitude is computed from the time the balance spends crossing the lift angle. Report a smaller angle than the truth and the machine concludes the balance is swinging further than it is; report a larger angle and it concludes the opposite. The error is roughly proportional, so a 15% error in the angle is a 15% error in the amplitude — enough to turn a tired movement into a healthy-looking one.
Many machines default to 52 degrees. That default is a convenience, not a specification, and it is wrong for a large share of modern movements.
The claim this bench will defend
The bench holds that the default lift angle is the single most common cause of a false amplitude reading in amateur timing, and that the fix costs nothing. Anyone who reports amplitude without the angle should be asked for it before the number is discussed.
References
- Ref 1Understanding Amplitude in Movement Phenomena, Fondation de la Haute Horlogeriesupports the amplitude definition that depends on the lift angle
- Ref 2Time and Frequency from A to Z, Q to Ra, NISTsupports the terminology used for the time and frequency figures quoted
- Ref 3Understanding Jewels in Watch Movements, Fondation de la Haute Horlogeriesupports the jewel-and-roller description the angle belongs to
One link, one document, titled as it titles itself. No home pages, no search results.
Set this page down Set this page down when you know the angle for your movement and have set it.