Seiko (SII) Caliber NH36 Watch Movement

The Seiko Instruments (SII) caliber NH36 (NH36A) is a hand-windable, hacking upgrade from the Seiko caliber NH26A (read: NH25A vs NH35A). Seiko Instruments labels the NH calibers as part of the “Basic” Mechanical Series.

Some of the topics covered in this caliber listing:

• NH36A VS 4R36A
• NH36A VS NH35A
• Accuracy
• Winding the Mainspring
• Crown Position Functions
• Rotor Variations
• Replacement Price

NH36A VS 4R36A:

It’s also important to note that the Seiko NH36A movement is basically an unbranded version of the Seiko caliber 4R36 found in the Next Generation Orange Monster. In other words, the 4R36 is used in Seiko branded watches, the NH36 is sold to other brands for use in non-Seiko watches.

NH36A VS NH35A:

One of the most popular watch movements available right now is the Seiko Instruments caliber NH35A. The NH35A and NH36A are very similar and both are based on the same Seiko NH family of movements. The main difference is that the NH36A has a complication to display the day of the week and the date, whereas the NH35A only has a date.

Accuracy:

In the technical documentation, Time Module claims that the NH36A accuracy range is within -20~+40 seconds per day under normal conditions.

These accuracy measurements were recorded without the date complication being active. This shouldn’t have any noticeable bearing on the accuracy, but it’s interesting.

Note: When you attempt to get a measurement of your watch’s accuracy, it’s important to make sure your watch is fully wound or the lack of power reserve may skew the test results. TMI states that measurements should be done within 10-60 minutes after the movement is fully wound up.

Winding the Mainspring:

The NH36A should be fully wound after about 55 manual turns of the crown. This movement is also equipped with the Seiko Magic Lever, so shaking the watch side to side should get it going almost immediately. You cannot overwind it. A full wind should get about 40 hours of runtime.

Crown Position Functions:

• 0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
• 1 (pulled out one click): Clockwise = Day setting / Counterclockwise = Date setting
• 2 (pulled out two clicks): Time setting clockwise and counterclockwise

When in position 2, with the crown pulled out two clicks, the seconds hand should stop. This is what is called hacking.

Rotor Variations:

While many watch brands that use the NH36A will opt for a custom rotor (oscillating weight), as of the official tech sheets from March 2017, two stock rotors are available depending on the country of origin: Japan or Malaysia.

Replacement Price:

At the time of this post, replacement prices for the caliber NH36A were found online for around $38.27 USD. Buy it here

Additional Resources:

• NH36A technical drawings (pdf)
• NH36A instructions manual (pdf)
• Also read: Seiko NH Caliber Comparison/Differences
• The difference between SII and TMI
• Related caliber: Seiko NH35