“Seiko Mod Movement Review: Which One to Choose?”

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Seiko watch modification tools and parts on a workbench

Seiko watches have been a staple in the watchmaking industry for over a century, renowned for their quality, durability, and timeless design. As a result, they have become a favorite among watch enthusiasts for modding. This article delves into the world of Seiko modding, exploring popular models, understanding different movements, comparing the NH34A and NH35A movements, and providing a step-by-step guide to modding your Seiko watch. Whether you’re a seasoned modder or a beginner, this comprehensive review will help you choose the perfect Seiko movement for your next modding project.

Key Takeaways

  • Seiko watches are an excellent choice for modding due to their high quality and durability.
  • Popular Seiko models for modding include the SKX007, Turtle, and Alpinist.
  • Understanding the differences between mechanical, quartz, and spring drive movements is crucial for successful modding.
  • The NH34A and NH35A movements are popular choices for Seiko mods, each with its own technical specifications and performance characteristics.
  • Essential tools for Seiko modding include movement holders, case openers, and dial protectors.

Popular Seiko Models for Modding

When it comes to Seiko Mod Review, certain models stand out as favorites among enthusiasts. These cult classic Seiko designs offer a robust platform for customization, allowing for a wide range of creative modifications. Let’s explore the world of Seiko mods with diverse models like Seiko 5, Turtle, and SSK. This community-driven culture fosters creativity and innovation in customizing Seiko watches.

Understanding Seiko Watch Movements

close-up of Seiko watch movement with gears and cogs

Seiko watches have been around for over a century, and their reputation for quality and durability has made them a popular choice among watch enthusiasts. Seiko’s movements are no exception, with the NH34A and NH35A movements being two of the most popular choices for Seiko watch mods. But what exactly is the difference between these two movements, and how do they affect mod compatibility? In this article, we’ll explore everything you need to know about the Seiko mod compatibility of NH34A vs NH35A.

Mechanical Movements

Mechanical movements are the heart and soul of traditional watchmaking. These movements are powered by a mainspring and require manual winding or automatic winding through the motion of the wearer’s wrist. Seiko’s mechanical movements are known for their reliability and craftsmanship, making them a favorite among watch modders.

Quartz Movements

Quartz movements, on the other hand, are powered by a battery and regulated by a quartz crystal. These movements are highly accurate and require less maintenance compared to mechanical movements. Seiko’s quartz movements offer a great balance of precision and affordability, making them a popular choice for those looking for expert insights on customizing Seiko watches.

Spring Drive Movements

Spring Drive movements are a unique hybrid of mechanical and quartz technologies. They use a mainspring for power but regulate time with a quartz crystal, offering the best of both worlds. This innovative technology provides exceptional accuracy and a smooth sweeping second hand, setting Seiko apart in the watchmaking industry.

Comparing NH34A and NH35A Movements

close-up of Seiko watch movement, NH34A and NH35A comparison, detailed watch mechanism, horology, precision engineering

Technical Specifications

At first glance, the NH34A and NH35A movements may seem nearly identical. They both feature a 3 o’clock crown position, a 41-hour power reserve, and a frequency of 21,600 beats per hour (BPH). However, there are some key differences between the two movements that can affect mod compatibility.

Specification NH34A NH35A
Date Wheel Position 4:30 3:00
Stem Height 7.50mm 6.00mm

Performance Differences

The most significant difference between the NH34A and NH35A is the position of the date wheel. The NH34A features a date wheel at the 4:30 position, while the NH35A has a date wheel at the 3 o’clock position. This may not seem like a major difference, but it can affect the placement of the dial and hands in a watch mod.

Another difference between the two movements is the height of the stem. The NH34A has a stem height of 7.50mm, while the NH35A has a stem height of 6.00mm. This can affect the compatibility of certain watch cases and crowns, as the stem height must match the case and crown specifications.

Mod Compatibility

When choosing between the NH34A and NH35A for a mod, it’s important to consider your specific needs and preferences. If you want a wider range of dial and hand options, the NH35A may be the better choice. However, if you prefer the 4:30 date position or need a higher stem height for your case and crown, the NH34A may be the way to go.

Expert advice on customizing your timepiece: Techniques include bezel insertion, case refurbishment, and lug hole drilling. Movement upgrades for precision, functionality, and reliability.

Essential Tools for Seiko Modding

When it comes to Seiko modding, having the right tools is crucial for a successful project. Quality tools are key to ensuring that your modifications are precise and durable. Here are some essential tools you will need:

Movement Holders

A movement holder is indispensable for keeping the watch movement secure while you work on it. This tool helps prevent any damage to the delicate components of the movement.

Case Openers

Case openers are used to safely open the watch case without scratching or damaging it. They come in various types, including knife-style and screw-back openers, to suit different case designs.

Dial Protectors

Dial protectors are essential for safeguarding the watch dial during the modding process. They prevent scratches and other damage that can occur while working on the watch.

Remember, larger parts like the case and crystal are easy to remember, but smaller components such as gaskets or click springs are often forgotten. This Seiko modding guide covers the description and usage of each item to help you understand how they fit together in a watch build.

Step-by-Step Guide to Modding a Seiko Watch

watch modification tools and Seiko watch on a workbench

Modding a Seiko watch involves several precise steps to ensure a successful transformation. This guide will walk you through the essential stages of the process, from disassembling the watch to reassembling and testing it.

Disassembling the Watch

To start, you need to carefully disassemble your Seiko watch. Precision and care are crucial at this stage to avoid damaging any components. Use a case opener to remove the back cover and a movement holder to secure the watch movement. Make sure to document each step for easy reassembly.

Installing the New Movement

Once the watch is disassembled, you can proceed with installing the new movement. Ensure that the new movement is compatible with your watch model. Align the movement correctly and secure it in place using the appropriate screws and tools. Double-check all connections to ensure proper functionality.

Reassembling and Testing

After installing the new movement, reassemble the watch by following your documented steps in reverse order. Pay special attention to waterproofing seals to maintain the watch’s water resistance. Finally, test the watch to ensure it is functioning correctly and make any necessary adjustments.

Modding Seiko watches involves precision and care. Online resources and community support are available for beginners.

Common Mistakes to Avoid in Seiko Modding

watchmaker's bench with Seiko watches and modding tools

Incorrect Movement Installation

One of the most common mistakes in Seiko modding is incorrect movement installation. Ensuring the movement is properly aligned and secured is crucial for the watch’s functionality. Misalignment can lead to inaccurate timekeeping and even damage the movement.

Using Incompatible Parts

Using parts that are not compatible with your specific Seiko model can cause significant issues. Always verify that the parts you are using are designed for your watch model. This includes checking the size, fit, and compatibility of each component.

Neglecting Waterproofing

Neglecting to properly waterproof your modded Seiko can result in moisture damage. Make sure to replace all gaskets and seals, and test the watch for water resistance after completing your modifications.

When modding your Seiko, attention to detail is key. Overlooking small steps can lead to bigger problems down the line. Explore custom dials, sapphire crystals, movement selection, and the Seiko mod community for personalized and reliable watch customization.

Where to Buy Seiko Mod Parts

When it comes to sourcing parts for your Seiko modding projects, there are several reliable options available. Whether you prefer shopping online or visiting specialty stores, you can find everything you need to create your custom timepiece.

Online Retailers

Online retailers are a one-stop shop for Seiko mod parts. Websites like namokiMODS, Island Watch, and Seiko Mods offer a wide range of components, from dials and hands to cases and bezels. These platforms often provide detailed product descriptions and customer reviews, making it easier to find the right parts for your project.

Specialty Stores

For those who prefer a more hands-on shopping experience, specialty stores can be a great option. These stores often have knowledgeable staff who can offer advice and recommendations. Some popular specialty stores include local watch repair shops and dedicated watch modding stores. These locations can be particularly useful for finding unique or hard-to-source parts.

Community Recommendations

The Seiko modding community is a valuable resource for finding the best places to buy parts. Forums, social media groups, and online communities are filled with experienced modders who can offer recommendations based on their own experiences. Engaging with the community can also provide insights into the latest trends and popular modifications.

Engaging with the Seiko modding community can provide invaluable insights and recommendations, helping you find the best parts for your project.

Looking to customize your Seiko watch? Discover a wide range of Seiko mod parts at our online store. From bezels to dials, we have everything you need to make your watch truly unique. Visit our website today and start your customization journey!


In conclusion, choosing the right Seiko movement for your modding project depends on your specific needs and preferences. Both the NH34A and NH35A movements offer reliable performance and are highly regarded within the watch modding community. Whether you are looking for durability, ease of modification, or specific features, Seiko’s range of movements provides ample options to create a unique and personalized timepiece. With the right parts and a bit of know-how, you can transform a standard Seiko watch into a customized masterpiece that perfectly suits your style and needs. Happy modding!

Frequently Asked Questions

Which Seiko Watch Should I Mod?

Seiko watches are an excellent choice for modding due to their high quality. You can mod a Seiko for a long time before you require a new timekeeper. Additionally, many Seiko watches look great, both original and modded. That being said, there are a few Seiko watches you have to choose for modding.

Which Seiko Automatic Movement is the Best?

The ‘best Seiko watch movement’ saga continues. So far, we spoke about the 6R and 7S families of Seiko’s mainstream automatic watch movements and drew a bit of a comparison between the two. Their designs in their lineages stay pretty much the same; it’s their build and material quality that got enhanced over time.

What is the Difference Between NH34A and NH35A Movements?

Seiko’s movements are no exception, with the NH34A and NH35A movements being two of the most popular choices for Seiko watch mods. The difference between these two movements lies in their technical specifications and mod compatibility.

Which Seiko Watches are Most Accessible for Modding?

Seiko has a huge selection of dive watches available, and sometimes it’s hard to decide which one to pick. Some of the most accessible Seiko watches to mod include the SKX007, Turtle, and Alpinist.

What Movement Fits What Case?

There is a whole ecosystem providing parts for Seiko modders. It’s important to know which movement fits which case to ensure compatibility and avoid common mistakes.

Where Can I Buy Seiko Mod Parts?

Crystaltimes USA offers the best Seiko watch parts in the market today. From Seiko sapphire crystals, cases, bezels, crowns, dials, movements, and more, you can shop online from various retailers and specialty stores.

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