How to assemble an NH35

How to Assemble a Watch with a Seiko NH35 Movement: A Step-by-Step Guide

Assembling your own watch with a Seiko NH35 movement is one of the most popular and rewarding projects in the world of amateur watchmaking. This movement is robust, ultra-reliable, and boasts the largest catalog of compatible parts (cases, dials, and hands) on the market.

Here is the ultimate assembly guide, explained step by step.

🛠️ Essential Tools

To successfully complete this project, you only need this basic kit:

  • Movement holder: To securely hold the movement.

  • Hand press or pushers: Essential for fitting the hands without bending them.

  • Rodico: Cleaning putty used to hold hands and remove fingerprints.

  • Fine tweezers: With thin tips for manipulating small components.

  • Case back wrench: To seal the case tightly when finished.

  • Latex finger cots: To avoid leaving body oils on the movement or dial.

🏗️ Step-by-Step Assembly Guide

Step 1: Removing the Provisional Stem

The NH35 movement comes from the factory with a gray plastic stem that protects the mechanism.

  1. Place the NH35 in the movement holder.

  2. Locate the small metal release button (only visible when the stem is in the normal operating position).

  3. Gently press the button with tweezers and remove the plastic stem.

Step 2: Installing the Dial

The dial has two small feet (pins) on the back that must fit into the holes of the gray plastic spacer on the movement.

  1. Align the dial feet with the holes in the movement (make sure to check if your case is designed for the crown at 3 o'clock or 4 o'clock).

  2. Gently press the dial down until it is completely flat and secure.

💡 Revival trick: The dial feet are extremely fragile and break easily if too much force is applied or the angle is incorrect. If the pins break, do not discard the dial. You can fix it by completely cutting off the remaining stubborn pin and using small pieces of heavy-duty double-sided tape (or special circular dial adhesives) strategically placed on the plastic spacer to firmly secure the dial.

Step 3: Attaching the Hands (The Critical Point)

Turn the provisional stem until you see the date change exactly at 12:00. That precise moment is your reference point.

  1. Hour hand: Place it pointing exactly at 12:00. Use the hand pusher to press it evenly. It should be perfectly parallel to the dial.

  2. Minute hand: Recheck that everything is aligned at 12:00 and press the minute hand into the same position. Turn the stem to check that the hour and minute hands move parallel without rubbing against each other or touching the dial markers.

  3. Second hand: This is the most complex due to its millimeter-sized arbor. Assist yourself by placing a tiny bit of Rodico on the tip of a toothpick to present the hand over the central arbor. Once you feel it has engaged, press it firmly with the pusher.

Step 4: Inserting the Movement into the Case

  1. Remove the stem by pressing the release button again.

  2. Ensure the inside of the steel case is completely clean.

  3. Carefully insert the compact block (movement + dial + hands) through the back of the case, perfectly aligning the stem channel of the movement with the crown tube of the case.

Step 5: Cutting and Adjusting the Final Stem

The steel stem that comes with your case's crown is too long and must be cut to size.

  1. Insert the long stem all the way in and measure the exact millimeter length that is superfluous between the case and the crown.

  2. Remove the stem and cut off the excess with clean cutting pliers.

  3. Apply a tiny drop of threadlocker (like Loctite blue) to the threaded end and screw on the final crown. Reinsert it into the watch.

Step 6: Sealing and Closing the Case Back

  1. Place the black rubber gasket on the case thread (a little silicone grease will maintain its waterproof properties).

  2. Screw on the metal case back by hand, being careful not to cross-thread it.

  3. Secure the closure using the case back wrench with firm but controlled pressure.

Your personalized watch with a Seiko NH35 heart is ready! Give the crown about 20 manual turns to wind the mainspring, set the time, and enjoy a unique piece assembled with your own hands.