The NH35A movement: specs, accuracy and why it is used
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The NH35A is a mechanical automatic movement made by Seiko Instruments (SII) for other watch brands. It has 24 jewels, beats at 21,600 vibrations per hour, holds about 41 hours of power reserve, and offers hacking seconds, hand-winding and a date. Its published accuracy spec is about -20 to +40 seconds per day.
NH35A specifications
| Spec | NH35A |
|---|---|
| Type | Mechanical automatic with hand-winding |
| Beat rate | 21,600 vph (6 beats per second, 3 Hz) |
| Jewels | 24 |
| Power reserve | About 41 hours |
| Accuracy (spec) | About -20 to +40 seconds per day |
| Hacking seconds | Yes |
| Functions | Hours, minutes, seconds, date |
| Quickset date | Yes, via the crown |
In short: 21,600 vph makes the seconds hand move in six small steps a second, so it appears to sweep. Jewels are synthetic bearings that cut friction at wear points. 41 hours means it keeps running for more than a day and a half off the wrist.
NH35 or NH35A?
In practice, the same movement. NH35A is the name of the version sold as a loose movement to watchmakers, and the two names are used interchangeably. Its close sibling, the NH36, adds a day display.
Why so many watches use it
- Proven reliability. Robust, relatively simple, made in large numbers for years; watchmakers know it well.
- Features of pricier movements. Hacking and hand-winding are not a given at this price.
- Easy to service. Almost any watchmaker can work on it, and parts are available.
- Made for customisation. Standard dimensions mean a wide range of compatible dials and hands, which is why it powers custom watches.
How accurate is the NH35A?
The manufacturer's spec is about -20 to +40 seconds per day, a wide range that covers temperature, position and state of wind. Many NH35As run better in practice, but we do not promise more than the published spec.
- State of wind: a watch worn all day with a full spring tends to be steadier.
- Resting position: dial up or crown down overnight can change the rate slightly.
- Magnetism: a strong magnet can make it run very fast; a watchmaker can demagnetise it in seconds.
See automatic vs quartz.
Using the crown
| Crown position | Function |
|---|---|
| Pushed in | Hand-wind the mainspring |
| First click out | Quickset date |
| Fully out | Set the time; seconds hand stops |
Do not change the date roughly between 9 pm and 3 am, when the date wheels are engaged. Full steps in watch care.
Servicing
Like any mechanical movement, the NH35A benefits from periodic service: cleaning, oiling and regulation. There is no fixed interval for everyone; a sensible rule is to see a watchmaker when accuracy changes noticeably or the reserve shortens. Because it is so common, service is usually simple and available.
The NH35A in ATÉRET watches
Every ATÉRET watch runs on an NH35A in a 39 mm stainless steel case with sapphire crystal. Some dials have a date window at 3 o'clock and some cases add a date magnifier. Design yours in the builder: ₪790 to ₪940.
Frequently asked questions
Who makes the NH35A?
Seiko Instruments (SII), the Japanese company that supplies movements to other watch brands. NH35A is the version sold as a loose movement.
What is the NH35A power reserve?
About 41 hours from a full wind.
Does the NH35A hack?
Yes. Pull the crown fully out and the seconds hand stops for precise setting.
How accurate is the NH35A?
The published spec is about -20 to +40 seconds per day; many run better in practice.
NH35 vs NH36?
The NH36 adds a day-of-week display; otherwise they are nearly identical.
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