If you’re searching for a Seiko Santos mod on a budget, this guide is perfect for beginners looking to build your own iconic square dress watch homage, inspired by the Cartier Santos. (Don’t want to build it buy it here)
Similar to our popular Beginner’s Tool Kit, this is a curated list of compatible parts to create a reliable, stylish Seiko Powered Santos-style watch using affordable sources like AliExpress (with our affiliate links for easy sourcing).
Everything in this guide is intended to work together seamlessly for a straightforward assembly. If you swap parts, we’ve included key sizes to help you source alternatives or even custom options.
You’ll need basic tools to assemble—grab our Budget Starter Toolkit for everything essential.
For full step-by-step instructions on building with pre-assembled cases, check our Guide to Seiko Santos Mods in Pre-assembled Budget Cases.
Movement: TMI (Hattori / Seiko) NH35
The heart of this watch is the reliable NH35A automatic movement from Time Module Inc. (TMI), part of the Seiko/Hattori group. This is the go-to choice for modders due to its robustness, availability, and reasonable pricing.
Key Features:
- Automatic self-winding with manual hand-winding capability
- Hacking seconds (stops when setting time for precision)
- Date complication at 3 o’clock~41-hour power reserve
- Beats at 21,600 bph for smooth sweeping seconds Rated accuracy: -20 to +40 seconds per day (often performs better when regulated)
The NH35A is essentially identical to the 4R35 found in current official Seiko watches—same dimensions, functions, and compatibility with dials/hands.
Recommended AliExpress link: NH35 Movement (~£80)
Hand Hole Sizes (critical for compatibility):
- Hour: 1.50mm
- Minute: 0.9mm
- Second: 0.2mm
Learn more in the NH3X Movements Blog.
There are Chinese copies of the NH3X movement, so be sure to shop for Japanese NH35.
Case and Bracelet: 38mm Stainless Steel Seiko Santos Mod
We recommend a stainless steel case and bracelet set complete with sapphire crystal, fixed stainless steel bezel, and an exhibition caseback. The case features a square design with polished screws for that classic aesthetic, and it’s secured with 16 screws on the back for easy access. Water resistance is rated at 30m with proper assembly.
This 38mm size offers a modern, versatile wrist presence while staying true to the elegant proportions of the original inspiration. The case comes pre-fitted with crown and tube, as well as gaskets for easy assembly.
Sizes
- Width is 38mm (44mm with crown)
- Lug-to-lug is 44.8mm
- Height is 12.3mm.
Pro Tip: We recommend buying a bracelet and case set if you intend to wear your watch on a bracelet or see yourself wanting one in the future. The integrated design ensures a flush fit and better comfort. We have assembled a number of these from different supplier and the quality varies and the bracelet were not compatible with one and other.
Read more in our Blog about Bracelets and Seiko Modding.
Recommended Ali Express options: Steel Case and Bracelet Set (less than £40, including bracelet)
Dial: Personal Choice
The dial is really a personal choice and what makes this mod unique! For a classic look, go with a sterile (no logo) white or silver dial with Roman numerals and railroad track minute markers.
Key Specs for Compatibility:Diameter: 29.8mmThickness: 0.4mmSuitable feet position to fit NH35 movement with a 3 o’clock crown.
If you want something different or a custom dial made, these sizes ensure compatibility with most Santos-style cases.
Here are some popular budget options.
Dial Below with Text and customisation options requires a date wheel for 6 o’clock.
Dial Options for a Traditional Santos Homage (~£10-£20) Sterile Dial with Roman Numerals
Hands:
All of the dial options above come with the option to add your choice of classic homage hands. If you wish to go off piste you will need to reference the movement section above for the hand hole sizes or any hands suitable for the NH35 will fit this movement. Hand Length is important with this mod. The dial is on the smaller side of the NH35 dials and some minute and second hands maybe too long for the dial/case. Hand length can not exceed 10.5mm with this mod. All of the options below are made to work perfectly with this mod.
Recommended: Blue or silver color for the classic Santos look. If it is your first mod, it would be advisable to have a second set of hands which can be purchased on the link below.
AliExpress example: Lumed Hands (~£5) Without Lume
Date Wheel Mod
The dials with the date window at 6 o’clock will require an additional date wheel which can be purchased on the links below. This may be a little beyond a first time Modder as it requires the calendar works to be disassembled. Although this is not covered in the budget Santos guide, it can be found in the free members area of the site. It is certainly not unachievable for a beginners but it will require a little more time and patience. Sign up here.
AliExpres Lumed Date Disk / Wheel (£9.50)
Extra Stems
As a new Modder you may make mistakes and its best to be prepared for this to happen so that mods don’t get shelved until a new part arrives. This mod requires cutting the stem to size to fit the case and crown. So pick up a couple of spare stems to have around, just in case.
Ali Express example: Pack or 5 (£2.50)
Is This Perfect?
It’s good enough to have a go with and won’t break the bank—you are not going to get the quality of a genuine Santos or even a high-end homage, but you will have a watch that is water-resistant (typically 30m with proper assembly) and suitable for everyday wear. It’s a fun, rewarding project with great bang-for-buck performance, powered by a proven Seiko movement.
Check List
Total parts cost: ~£120-150 depending on options.Ready to start your Seiko Santos mod? Grab the parts, toolkit, and dive in with this guide! Don’t forget if you don’t, won’t or can’t assemble it yourself you can buy it here!
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