⚙ TESTING & REGULATION

Regulating Tool

Adjusts rate: an index regulator, or timing screws on a free-sprung balance.

Regulate Testing & Regulation 3D

Specification

Adjustment types	Index regulator · timing screws · weights
Typical sensitivity	A few seconds per day per small movement
Index range	±30 s/day typical
Free-sprung range	Broader, and more stable
Beat error adjustment	Hairspring stud position
Tooling	Regulator tool, screwdriver, tweezers
Measurement	Requires a timegrapher
Positions	Regulate across the range, not one position

Technical parameters

Mechanism	Active hairspring length or balance inertia
Precondition	Healthy amplitude and low beat error
Verification	Multiple positions, over time
Stability	Free-sprung resists shock better
Risk	Improper tool contact destroys a hairspring

Use magnificationAvoid magnetismVentilate

Overview

Regulation changes the rate by changing the effective length of the hairspring. On an index-regulated movement, moving the regulator index shifts the curb pins along the outer coil, which shortens or lengthens the active portion of the spring. Moving it one way makes the watch run faster, the other slower.

On a free-sprung balance there is no index at all. Rate is set by changing the inertia of the balance wheel itself, either by turning timing screws outward to slow it or inward to speed it, or by moving weights on a rim. It is slower to adjust and much more stable afterwards, because there are no curb pins to introduce positional variation.

Regulation is the last step, not the first. Before touching it, amplitude has to be healthy, beat error has to be low, the escapement has to be in good order, and the movement has to be clean and correctly oiled. Regulating a movement with a real fault just produces a watch that runs well in one position and badly everywhere else.

What matters about it

Sets the rate by changing effective hairspring length
Index regulation is quick; free-sprung is stable
Beat error is adjusted at the stud, not the index
Regulation is the final step, after every fault is fixed
Adjustments must be verified in several positions

SafetyThe regulator sits directly over the hairspring, which is the most fragile part in the watch. A slip with a steel tool destroys the spring instantly. Use the correct tool, support your hand, and never touch the coils themselves.

Practical notes

Confirm amplitude and beat error before moving the regulator at all.
Make small adjustments and allow the movement to settle between readings.
Regulate to the average across positions, not to a perfect dial-up reading.
On a free-sprung balance, move opposing screws in matched pairs to preserve poise.

Compatible with

Index-regulated movementsFree-sprung balancesSwan-neck regulatorsVintage and modern balances

Specifications on this page describe generic families and published reference values, not a specific product. Nothing here is for sale, no result is guaranteed, and no page endorses a commercial brand. Follow the documentation for the movement or tool actually in front of you.

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