NH35 Movement Explained: Accuracy, Specs & Service

The NH35A is an automatic movement with a date, hand winding and stop seconds. Choose it for a date window; if you also need the weekday, compare the NH36A. The TMI specifications below explain its power reserve, published accuracy and dimensions for selecting compatible components.

Published TMI specifications for NH35A

Accuracy: keep the two published contexts separate

The NH3 Technical Guide describes a rate test 10–60 minutes after full winding, with a lift angle of 53°, in dial-up, 9-up and 6-up positions. It calls for 20 seconds of stabilisation followed by at least 20 seconds of measurement in each position; it does not specify a temperature. The individual 2022 NH35A specification sheet instead gives 23 ± 2 °C and a 20-second accuracy test. Both documents state the published −20 to +40 seconds per day tolerance, but neither turns it into a prediction for a finished watch.

For a useful observation, compare starting and ending offsets against one time reference and record the elapsed time, wearing and resting conditions. The guide to measuring an automatic watch's daily rate explains the record to take to a watchmaker if a pattern persists.

Power reserve, winding and useful service notes

TMI states more than 41 hours of power reserve with a fully wound mainspring. That is a stated test condition, not a fixed period of use or a measure of how much winding any day of wear supplies.

If a watch stops or its observed rate changes, write down the timing result, whether it followed an impact, possible magnetism or visible moisture, and the conditions in which it was worn or stored. That gives a qualified watchmaker useful facts for the individual assessment. The watch-care guide covers ordinary care.

Date setting, hand winding and stop seconds

NH35A has automatic winding, hand winding, stop seconds and a date; it has no day display. The Technical Guide gives date quick-setting in the first crown position, with the crown turned left. The second crown position sets the time with the hour and minute hands. Do not set the date between 21:00 and 04:00, the prohibited date-correction interval stated in the guide.

Hand winding lets you wind the mainspring with the crown without wearing the watch. Automatic winding uses the rotor as the watch moves. Stop seconds holds the seconds hand during time setting, making it easier to synchronise with a time reference.

Check dial feet, calendar opening, hand fittings, case, movement holder, spacer and clearance as one component set. A movement name and diameter alone do not document a complete fit.

For other calibre choices, read the Seiko movement comparison and the Miyota movement guide.

For a Seiko 5 donor, verify the exact reference and installed movement before choosing replacement parts; the family name alone does not establish compatibility.

A concrete NH35 model

MARINER MOD - BLACK is a MedoMods model specified with NH35. Its product page supplies the configuration details for that watch; the movement figures above remain useful for reading those details.

For a service quote, ask whether cleaning, lubrication, replacement of worn parts, a rate check and an assessment of the case seals are included. Compare the complete work and terms for your watch; the calibre figures do not set a service price or maintenance interval.

Further reading

• NH35 vs NH36 – date or weekday as well.
• NH35 in mod watches – compare models and functions.
• Configurator – select the available combinations.
• Glossary – look up the technical terms.

Frequently asked questions

How accurate is the NH35 really?

TMI states −20 to +40 seconds per day as a static movement specification. The rate of your finished watch needs to be measured; the accuracy section explains the separate test conditions in the specification sheet and Technical Guide.

How long does the NH35's power reserve last?

TMI states more than 41 hours with the mainspring fully wound. It does not establish a fixed period of use or say that daily wear fully winds every watch.

Can I regulate the NH35 myself?

Yes, the movement has a regulator for rate adjustment. A useful adjustment requires suitable timing equipment and experience with the movement. Have a watchmaker regulate it if you do not have those prerequisites.

When should the NH35 be serviced?

The linked TMI documents do not give a universal service interval for every finished watch. Have a persistent rate change or an issue following an impact, suspected magnetism or moisture assessed by a watchmaker, and bring your observations.

Does every dial for Seiko mods fit the NH35?

No. The dimensions and a shared movement name do not prove that a particular dial, hands, case, spacer and calendar layout fit together. Verify the exact component documentation.

Sources

• TMI NH0/NH3 product line, checked 9 October 2026.
• TMI NH35A specification and drawing, revised 16 November 2022, checked 9 October 2026.
• TMI Cal. NH3 Technical Guide and Parts Catalogue, Version 03, checked 9 October 2026.