The NH35: Why It’s the Modder’s Best Friend
Bulletproof. Customizable. Affordable. No wonder it’s king.
Ask any seasoned modder what movement they recommend for a first (or fiftieth) build, and you’ll probably hear: NH35.
So why does this Seiko-built movement dominate the modding world?
📅 Reliable as hell — It can take a beating and keep ticking.
💲 Inexpensive — You won’t cry if you scratch one.
🔌 Compatible — Tons of aftermarket parts are made for it.
🕒 Modern feel — Hacking + hand-winding for budget builds.
Every Carbon Chrono dial is designed to fit NH35 (and NH36) builds — so whether you’re going for diver, field, or wild experimental, you’re covered.
If you’re new to watch modding, the NH35 is your playground.
If you’re experienced? You already know the deal.
Build bold. Break nothing. Build again.
How would you build it?
Don’t let a tiny part screw up your mod — get your spring bar sizing right.
When it comes to modding your watch, most of the attention goes to dials, hands, crystals, and bezels. But ignore your spring bars at your peril — those little metal rods are the only thing keeping your strap (and watch) from flying off your wrist and into the abyss.
So how do you choose the right spring bar size?
Let’s break it down — quick, clean, and modder-friendly.
What Is a Spring Bar?
It’s that small, spring-loaded metal rod that connects your strap or bracelet to the watch case. It sits between the lugs and holds everything together.
If the bar is too short? It’ll slip out.
Too long? You’ll damage your lugs.
Wrong thickness? It won’t fit the strap.
Wrong shoulder type? Good luck getting it out later.
Spring Bar Length = Lug Width
This is the golden rule:
Your spring bar length should match your watch’s lug width.
Here’s a quick size reference:
Strap / Lug Width Spring Bar Length
18mm / 18mm spring bar
20mm / 20mm spring bar
22mm / 22mm spring bar
24mm 24mm spring bar
Not sure your lug width? Measure it with calipers, or look up your case specs.
Spring Bar Thickness: 1.5mm is Standard
For most builds — especially NH35-based divers or dress cases — a 1.5mm thick spring bar will do the job.
That said:
Thicker spring bars (1.8mm–2.0mm) = tougher, but may not fit narrow strap holes
Thinner spring bars (1.2mm) = better for tight spaces or vintage-style straps
Stick to 1.5mm unless you’ve got a reason to go thicker or thinner.
Shoulder or No Shoulder?
Spring bars come with or without “shoulders” (the little notches near the tips that help with tool removal).
Shouldered spring bars: Easier to remove, good for regular strap changes
Shoulderless bars: Cleaner look, but a pain to remove without a tool made for it
For modding, we recommend shouldered spring bars — especially if you like switching things up.
Bonus Tip: Curved Spring Bars for a Cleaner Fit
Using a strap that curves tightly around the case? Curved spring bars give a better fit and help avoid lug rub.
TL;DR – The Modder’s Spring Bar Checklist
✔ Match the spring bar length to your lug width (e.g. 20mm lugs = 20mm spring bar)
✔ Stick with 1.5mm thickness unless you have a specific need
✔ Use shouldered bars for easy swapping
✔ Use curved bars for tight-fitting straps
Want a Quick Guide?
We’ll be publishing a printable spring bar + strap sizing chart in the Mod Lab soon — make sure you’re on the list.
And as always, before your next build, ask yourself:
How would you build it?
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