If you’re looking to upgrade a Seiko movement in a vintage seiko with a modern automatic movement, the NH36 movement is one of the best and most affordable options available. Many Seiko watches from the 1970s to 1990s—like the Seiko 7009, 7006, and 7019—were built with the robust base 7005 caliber. While these watches are known for running reliably for decades (some over 50 years without a service), more and more of them are now showing signs of age.
Why Upgrade a Seiko Movement?
Servicing a mechanical movement can be costly, and parts for some of the older calibers are getting harder to find. For many watch owners and modders, replacing the original 7000 series movement with a modern NH36 automatic movement is a cost-effective solution.
Not only does this breathe new life into an older watch, but it also gives you the added functionality of hacking and hand-winding, which weren’t available in the older Seiko calibres.
NH36 Compatibility with Seiko 7000 Series Cases
Luckily, the NH36 movement drops directly into most old Seiko 7000-series cases, especially those with crown positions at 3 o’clock or 3.8 o’clock—just like modern 4R series movements. These are very close in dimensions and layout, making them a natural fit for vintage Seiko conversions.
You’ll Likely Need a New Crown & Stem
To upgrade a Seiko movement you will likely need a new crown and stem. One of the small but critical differences is the stem, this can be used with the original crown if the original stem can be uncrewed. A Stem will be supplied with the NH36, but you may wish to buy more, as new modders bay cut the stem to short and need to start again. These can be purchased from Namoki or Ali Express, it is often useful to have a small stock of these on hand.
The tap size of the NH36 stem is 0.9mm or “Tap 9”. Should a crown need to be sourced it will need to be suitable for the NH36 tap size. When sourcing a crown consideration should be given to the “crown tube”, measuring this will allow you to confidently select a crown that will offer some water proofing properties. Thankfully a supplier on Ali Express has a crown to suit your 7005 to NH35 conversion.
NOTE: After upgrade manual operation of calender works will not be the same, for instruction on operation of the NH36 movement, click here.
Using the Original Dial with an NH36
You can reuse your original Seiko dial from the 7000 series, but you’ll need to modify how it’s mounted. The dial feet on the vintage Seiko dials won’t align with the NH36 movement’s holes. To solve this, most modders use dial dots or sticky dial feet to securely attach the dial to the movement or to the movement spacer. Check out our guide on attaching a dial using sticky dial feet.
Good News on the Hands
The Seiko NH36 uses the same hand sizes as the 7009, 7006, and similar movements:
- Hour hand: 1.50mm
- Minute hand: 0.90mm
- Second hand: 0.20mm
This means you can reuse the original vintage Seiko hands with the NH36 movement, helping to maintain the original look of your watch while upgrading the mechanics inside. If you are looking for hand s
Pinion Height and Crystal Clearance
One important consideration when to upgrade a Seiko movement to the NH36 is that its pinions (the posts where the hands attached) are slightly taller than those on the 700X calibres (movements). This increased height may cause the hands to sit closer to the crystal—sometimes too close. In certain vintage Seiko cases, this could result in the hands brushing or sticking against the inside of the crystal. To avoid issues, you may need to install a slightly taller or domed crystal, which allows for proper hand clearance and reliable operation.
Final Thoughts from SeikoModder.com
Upgrading a vintage Seiko movement is a great way to preserve the look of a classic watch while adding the reliability and functionality of a modern movement. Whether you’re trying to avoid the cost of servicing an old 7005 base calibre or simply want to modernise your timepiece, swapping to an NH36 movement is one of the easiest and most rewarding Seiko mods out there.
At SeikoModder.com, we love seeing vintage Seikos get a new lease on life. With the right crown, dial mounting solution, and attention to crystal clearance, your upgraded Seiko will keep ticking for decades more.
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