Assemble Watches
How do you build your first Seiko mod?
No watchmaking experience required. This guide walks you through every part in the order you'll choose it, from the dial to the strap, with a short list of options at each step.
Assemble Watches is a free online Seiko mod builder and visualizer. You can plan an NH35 or NH36 build by mixing cases, dials, hands, bezels, and bracelets, check part compatibility (dial diameter, dial feet, lug width), and preview the finished watch before ordering — with no account needed. It is a planning tool, not a parts retailer.
Build your watch, step by step
This guide walks through nine parts and three tools, picked in order. Each step shows your build so far, then gives you a short list of options for what comes next.
Here's the order you'll pick them in:
- Dial: the face of the watch.
- Movement: the engine that drives the hands, usually an NH35.
- Hands: the hour, minute, and seconds hands.
- Case: the body that holds everything, often an SKX007 or SRPD.
- Bezel ring: the metal ring around the crystal.
- Bezel insert: the printed ring that sits inside the bezel.
- Chapter ring: the inner ring that frames the dial.
- Crown: the knob you use to set the time.
- Strap or bracelet: how the watch attaches to your wrist.
The dial, movement, hands, and case are the core of every build. The bezel ring, bezel insert, chapter ring, and crown are optional finishing parts. Putting it together takes three tools: a spring bar tool, a case back wrench, and a hand-setting tool.
What kind of dial do you want?
The dial is the face of the watch. It's the first thing anyone notices, and it sets the whole character of the build, from a clean three-hand look to something busier with a date window.
The five dials below are all from Namoki, and all include a date window. That matters now because it decides which movement you can use next.
Pick a dial above. It'll show up on the watch above the options.
What movement powers it?
The movement is the engine inside the watch. We're using the NH35 here, the most common movement for a first build. It hacks the seconds hand: the seconds hand stops when you pull out the crown, so you can set the time to the exact second. It can also be hand-wound, so it doesn't need a working automatic rotor to keep time on your bench.
Both options below are the same NH35 from Namoki. The only difference is the date wheel: one shows the date in white, the other in black. Pick whichever reads best against your dial.
That's your movement. It now sits behind the dial.
Continue in the builder to check fit and find supplier links →What hands do you want?
Hands have to fit your movement's hand-tube sizes, so they're sold matched to NH35/NH36-style movements rather than a generic fit.
Hands can also be lumed, meaning they hold light and glow in the dark, though none of the picks below are. If low-light legibility matters to you, look for lumed hands in the full builder. Pair them with a lumed dial so they match.
That's your hands. They're now on the dial.
Continue in the builder to check fit and find supplier links →What case holds it all?
The case is the platform everything else sits in. It's also the part most people start a mod from, since donor cases like the SKX007 are widely available and well documented.
Your case choice sets the lug width, which decides which straps and bracelets fit later, and whether a chapter ring is an option at all.
That's your case. The watch is taking shape.
Continue in the builder to check fit and find supplier links →Do you want a bezel ring?
The bezel ring is the metal ring that sits around the crystal. On a dive watch it's the part you turn, and it holds the bezel insert in place.
Not every case takes a separate ring. Some have a fixed bezel built in. The three below are all from Namoki and fit both SKX007 and SRPD cases. If your case uses a different platform, check that the ring matches it.
That's your bezel ring. It now wraps the edge of the case.
Continue in the builder to check fit and find supplier links →Which bezel insert?
The bezel insert is the printed ring that sits inside the bezel ring. It's where the dive scale, GMT numbers, or a classic Pepsi or Coke colorway lives.
The insert swaps without removing the movement, so it's one of the easier changes to make later. The three below are all from Namoki: one ceramic sub-style and two aluminum GMT options. Sapphire inserts are also available in the full builder.
That's your bezel insert. It now sits inside the ring.
Continue in the builder to check fit and find supplier links →Do you want a chapter ring?
A chapter ring sits between the dial and the crystal. It adds minute markers, color, or depth around the edge of the dial.
Not every case accepts one. If your case does, it needs to match the case platform.
That's your chapter ring. It now frames the dial.
Continue in the builder to check fit and find supplier links →Which crown finishes the case?
The crown is the small control on the side of the case. You use it to set the time and wind the movement.
Some cases include a crown. If yours does not, pick one that fits the case tube and stem setup.
That's your crown. The case has its control now.
Continue in the builder to check fit and find supplier links →Strap or bracelet?
A NATO strap is the easiest first choice. It needs nothing more than a spring bar tool and slides on in minutes.
A bracelet needs end links that match your case, so fewer options will fit than with a strap. Pick whichever suits how you want to wear the finished watch.
Straps
Bracelets
That's your watch, complete.
Continue in the builder to check fit and find supplier links →Here's your watch.
That's all nine parts: a dial, a movement to drive it, hands that fit, a case to hold it together, a bezel ring and insert, a chapter ring, a crown, and something to wear it on. None of these picks are final. Open the build in the full builder to swap any part, check compatibility, and find supplier links before you order.
| Dial | GS Birch Silver | $52 |
| Movement | Seiko (SII/TMI) NH35 Automatic Movement | $88 |
| Hands | 62MAS Black Finish | $22 |
| Case | NMK904 3 O'Clock SKX007/SRPD Watch Case: Polished Finish | $76 |
| Bezel ring | SKX007/SRPD Big Tooth Bezel: PVD Black Finish | $40 |
| Bezel insert | SKX007/SRPD Ceramic Bezel Insert: Sub style Black/White | $36 |
| Chapter ring | SKX007 Brushed Black Chapter Ring | $25 |
| Crown | SKX007 Big Crown: Polished Finish | $28 |
| Strap | Seatbelt NATO Strap: Black | $21 |
| Total | $388 |
Tools you'll need
- Spring bar tool (~$13) : for fitting the strap or bracelet.
- Case opener (~$10) : for getting into a screw-down case back.
- Hand press (~$19) : for seating hands without bending them.
- Movement holder (~$6) : to keep the movement steady while you work.
- Rodico (~$6) : a cleaning putty for dust and fingerprints on the dial.
Supplier links may be affiliate links. Tools without links are listed as requirements, not product recommendations.
Open this buildSee the full build guide for this watch →Where to learn how to mod
Assemble Watches handles the planning side. For step-by-step modding guides, these are the resources most people in the community point to first.
Namoki Mods
Beginner's guide and build tutorials
Namoki is one of the most trusted suppliers in the Seiko mod community. Their blog covers beginner guides, step-by-step build walkthroughs, and tool recommendations with photos throughout.
Lucius Atelier
Parts maker with a solid modding blog
Lucius Atelier makes well-regarded aftermarket parts and publishes genuinely useful modding guides on their blog. Good for understanding the process from people who build the parts themselves.
r/SeikoMods
Community wiki and resources
The most active Seiko modding community online. The subreddit wiki has guides, build logs, a parts compatibility FAQ, and a supplier list maintained by the community. If you have a question someone has already answered it here.
Tools you actually need
You don't need a full watchmaking bench. But you do need a few things, and skimping on them is where most beginners come unstuck. A $4 screwdriver kit from a dollar store will scratch your case, strip screw heads, and make you angry. Buy decent tools once. Read the full tools guide →
Links marked "Buy" go to a supplier. We may earn a small commission at no extra cost to you.
- Spring Bar Tool Buy →Absolutely essential. You'll use this every single time you change a strap. Get one with a forked end for lug bars.
- Case Back Wrench Buy →For screw-down case backs. A universal wrench covers most Seiko backs; don't improvise with pliers.
- Hand Setting Tool Buy →A basic hand setting tool. Essential for dial and hand work. Don't try this with tweezers.
- Movement HolderUseful for hand work. A soft cloth is enough for many first builds, but a holder makes the movement easier to control. No specific product recommendation yet.
- Rodico Putty Buy →A waxy cleaning putty for picking up dust and fingerprints off dials and hands. Cheap, indispensable, use it constantly.
- Watchmaker's Loupe (5-10x) Buy →Not essential, but it definitely helps. For checking hand clearance, spotting dust under the crystal, and generally not going in blind.
- Crystal PressOnly needed for crystal swaps, but if you're planning one, don't skip it. Using a poor quality press can damage the crystal. No specific product recommendation yet.
Helpful reading before you order
Worth reading before you commit to parts.
Tools
The Seiko mod tools guide
What to buy, what to skip, and where to get it. Covers everything from a spring bar tool to a crystal press.
Read →Dials
Dial selection and dial feet
How to check dial feet spacing and date aperture position before you buy, with curated compatibility resources.
Read →Movements
Movement and date matching
NH35, NH36, NH38, and NH34 differences explained, plus which dial date wheels match which movement.
Read →Compare
What is the best Seiko mod builder?
How Assemble Watches compares to spreadsheets, parts retailers, and prebuilt/assembly services.
Read →Ready to put something together?
Browse compatible parts, check dimensions, preview your build, and open supplier links before anything gets ordered.
Common questions
- What is Assemble Watches?
- It's a free watch mod planner and parts catalog for Seiko platforms. Select a case, dial, hands, bezel, and bracelet, verify compatibility automatically, and generate a parts list with supplier links before you buy anything.
- What is the easiest Seiko mod for a beginner?
- A strap or bracelet swap. It requires only a spring bar tool, takes under 10 minutes, and carries no risk of damaging the watch. A bezel insert swap is the next step up, around 15 minutes once you've done it once.
- Where can I learn how to actually mod a Seiko watch?
- Namoki Mods has a well-regarded beginner's guide on their blog. Lucius Atelier produces detailed step-by-step modding tutorials on YouTube. The r/SeikoMods subreddit has a community wiki with guides, build logs, and an active Q&A community.
- Are SKX007 and SRPD parts interchangeable?
- Most aftermarket dials, hands, and bezels sold as SKX-compatible also fit the SRPD (5KX series). Always confirm with the vendor that parts are listed as compatible with both platforms before buying.
- What's the difference between a bezel ring and a bezel insert?
- The bezel ring is the metal ring around the crystal, the part you turn on a dive watch. The bezel insert is the printed ring that sits inside it, carrying the dive scale, GMT numbers, or a Pepsi or Coke colorway. The insert swaps on its own without changing the ring.
- Do I need to change the bezel to mod a watch?
- No. The bezel ring and insert are optional finishing parts. A dial, movement, hands, and case make a complete build on their own. Swapping the bezel insert is one of the easiest ways to change the look later, so many modders start there.
- How much does a Seiko mod cost?
- A basic mod (strap or bezel swap) costs under $40 including tools. A full dial and hand build with sapphire crystal is typically $100–$190 in parts. A complete build from a donor case usually ranges from $190–$380.
- How long does it take to build a Seiko mod?
- A first full build usually takes one to two hours at a relaxed pace. A simple strap or bezel insert swap takes under 15 minutes. None of it is rushed, and you can stop and come back at any point.
- Do I need to pick every part in the guide?
- No. The guide shows you how the main parts fit together. You can stop at any point and open what you've picked so far in the full builder to keep going there.
- Can I change parts after I've gone through the guide?
- Yes. Opening your build in the full builder lets you swap any part, check compatibility, and find supplier links before you buy anything.
More questions? See the full FAQ or look up unfamiliar terms in the Glossary.