Seiko NH35/NH35a Movement (Everything You Need to Know)

The caliber Seiko NH35 movement (also known as the NH35A) is one of the most popular affordable, automatic movements currently on the market.

The NH35 has hacking and hand-winding, 24 jewels, a 41-hour power reserve, 21,600 bph, and a rated accuracy of -20 to +40 seconds per day.

The NH35 is equivalent to a non-branded Seiko 4R35 movement.

The NH35 is a popular choice amongst microbrands and watch modders for its affordability, reliability, and compatibility with a wide variety of watch cases.

Seiko-NH35a-movement-pats
ManufacturerSeiko
CaliberNH35A / NH35
Movement TypeAutomatic
Accuracy-20 to +40 seconds per day
Diameter27.40mm
Height5.32mm
Jewels24
HackingYes
Hand-windingYes
Vibrations per hour21,600 bph
Shock systemDiashock
Power Reserve~ 41 Hours
Winding DirectionClockwise
Country of ManufactureJapan or Malaysia
Known Watch BrandsSeiko, Invicta, Vostok, Lum-Tek, Spinnaker, Avi-8, etc. (see below for more)
Check PriceAmazon

NH35 Accuracy

The NH35 has a rated accuracy between -20 to +40 seconds per day under normal conditions. However, most NH35 owners find their movements to run much more accurately, often between -/+ 1 second to -/+ 10 seconds per day.

Seiko-Nh35a-movement-in-invicta-pro-diver-caseback

NH35 Lifespan

The NH35 is based heavily on the workhorse Seiko 7S26 movement which is known to last upward of 5-25 years without ever needing a service. This is due to the inclusion of plastic parts which reduce the need for frequent lubrication for maintenance.

NH35 Problems

The NH35 movement is a reliable, workhorse movement that is not known to have any recurring issues. Its reliability, for such an affordable movement, is one of the reasons it is so highly regarded.

Manufacturing Variations: Japan and Malaysia

The NH35a has two variations, manufactured in either Japan or Malaysia. From the factory, they can be easily distinguished by checking the engraving on the automatic rotor.

The rotor will have inscribed ‘Japan’ or ‘Malaysia’ depending on its country of manufacture.

Seiko-Nh35a-rotor-made-in-malaysia-and-japan

NH35 Service Costs & Frequency

Because the NH35 is such an affordable movement, often found for around $50 (check price), it is impractical to have it serviced by a watchmaker.

A service where a watchmaker disassembles, cleans, and regulates the movement can cost upwards of $100 or more, therefore it is more economical to replace the NH35 instead. 

View the video below to learn how an NH35a is dissasembled before a service.

Winding the Mainspring

Winding the mainspring, and charging the power reserve of the NH35 is simple.

  1. Ensure that the crown is in position 0 (pushed in toward the case).
  2. Rotate the crown clockwise (forward, if the watch dial is facing you).
  3. Rotate the crown for 55+ full rotations to fully charge the 41-hour power reserve.

Because the NH35 has an automatic mechanism, it is not possible to overwind, and exceeding the suggestion of 55+ rotations will not damage the watch.

Further, the rotor in the automatic mechanism will continue to wind the mainspring, and power the watch, while it’s on the wearer’s wrist. The rotor will constantly rotate, winding the mainspring with each rotation.

Setting the Time

In order to set the time:

  1. Ensure that the crown is in position 2, pulled all the way, two clicks away from the case.
  2. Rotate the crown freely, clockwise or counter-clockwise, until the hour and minute hands are in the correct place.
  3. Push the crown back down to position 0, toward the case.

Setting the Date

In order to set the date:

  1. Ensure the crown is in position 1, pulled just one click away from the watch case.
  2. Rotate the crown counter-clockwise, toward you, until the proper date is set.
  3. Push the crown in, toward the case.

NH35a vs NH36a

The NH35A and NH36A are both based on the Seiko 4R family of movements. The only difference is the NH35a only has a date complication, while the NH36a has day and date.

NH35a vs 7S26

The NH35 is essentially an unbranded upgrade of the Seiko 7S26 movement. The NH35, like the Seiko branded equivalent, the 4R35, has hacking and hand-winding, while the 7S26 does not.

NH35a vs Seiko 4R35

Seiko 4r36 movement through caseback 2
Seiko’s 4R36 movement, similar to the 4R35 and NH35a, with the addition of a day (instead of just a date) complication

The NH35a is essentially an unbranded Seiko 4R35 movement. Along with the 4R36 movement, the 4R35 is the primary modern movement Seiko uses in their entry-level Seiko 5 Sports models.

The NH35a and 4R35 are essentially the same build, with the same accuracy, specifications, and etc.

NH35 vs  Miyota 8215

The NH35 and Miyota 8215 movements are two of the most popular affordable Japanese automatic movements. The NH35 is slightly more expensive, but is said to be a bit more reliable than the Miyota 8215, and has a few extra features in its hacking and hand-winding.

The Miyota 8215 is known as a great entry-level workhorse movement that is reliable but suffers from faults such as an excessively loud rotor. Both are widely used in many microbrands and entry-level watch mods.

752px-Miyota8215
Miyota 8215 // Source: Rosstomson

NH35a vs Miyota 9015

The Seiko Nh35a and Miyota 9015 are two of the most popular Japanese automatic movements. One of the main differences between the two is their beat rate. The Nh35 has a slightly lower, 21,600 bph, while the Miyota 9015 has 28,800 bph, leading to a slightly smoother second-hand sweep.

The Miyota 9015 is specified to a slightly higher degree of accuracy than the NH35, coming in at -10 to +30 seconds per day, while the NH35 comes in at -20 to +40. Finally, the Miyota 9015 is a bit more expensive than the NH35, as it can most frequently be bought for ~$100 – $135, while the NH35 is more often found for around ~$60 – $80.

NH35 vs NH36

The NH35 and NH36 are almost identical movements, with one exception. The NH35 movement has just a date function, while the NH36 has both a day and date complication.

Brands that Use the NH35

Given the reliability, affordability, and availability of the Seiko NH35, many brands use the NH35 in some of their watches, including:

  • Seiko
  • Invicta
  • Vostok
  • Lum-tek
  • Spinnaker
  • Minus-8 Layer
  • Advisor Astro Helm
  • Advisor Ascent
  • BOLDR
  • Helm
  • Unimatic
  • Orion
  • Geckota
  • Benarus
  • AVI-8
  • Orthos
  • MWW
  • Scurfa
  • Air Blue
  • Dan Henry
  • Armida
  • Binger
  • G. Gerlach
  • Burei
Seiko-Nh35a-movement-in-invicta-pro-diver-caseback_2

Conclusion

The Seiko NH35a movement is one of the most popular non-swiss automatic movements on the market, and for good reason.

Its affordability, reliability, and availability make it an excellent choice for a microbrand, or watch modder. What the NH35 lacks in complications, it makes up for in its durability, and reasonable accuracy, once regulated.

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