A very good movement to start with.
Large ... started off as a pocket watch.
Size: 36.60mm diameter, 4.50mm height
Power reserve: 40+ hours .
(Wind Friday morning and the watch runs until Sunday evening).
Accuracy: -20 to +40 seconds per day
Beat rate: 21,600 vibrations per hour
Full wind: 35 half-turns of the crown
Hand-wound --- simpler with fewer parts.
The ST3600 includes 17 jewels at critical friction points.
mainsprings store energy,
gear trains transmit power
escapements regulate release.
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Disassembling a Seagull ST3600 (a pocket-watch movement similar to the ETA 6497) requires patience, steady hands, and an organized parts tray.
1. Preparation and Power Let-Down
- Remove hands and dial: Pull off the hands with a hand remover tool, then remove the dial. [1]
- Let down the power: Flip the movement over, trigger the click mechanism, and slowly let down the mainspring power until the balance wheel stops. [1]
- Remove the balance complete: Unscrew and carefully lift out the balance complete first. It is very delicate and protects the hairspring. [1]
- The balance wheel complete is made up of the hairspring, The balance cock,
- The balance wheel is the beating heart and primary regulating organ of a mechanical watch, functioning just like the pendulum in a grandfather clock
- A balance cock is a small bridge attached to the top plate of a watch movement that holds the upper pivot of the balance wheel assembly in place. Its not called the balance bridge because there is only one end. Its cantilevered
- T = Time (period of oscillation)
- I = Inertia (its the balance wheel itself)
- k= stiffness of spring ( Hair Spring)
- Key Parts of the Balance Assembly
- Balance Wheel: The oscillating wheel that regulates time.
- Balance Staff: The central axle or shaft on which the balance wheel turns.
- Hairspring (Spiral Spring): The fine coil that returns the balance wheel back and forth.
- Roller & Impulse Jewel: The part that interacts with the pallet fork to receive energy.
- Balance Cock (Bridge): The cantilevered arm secured by a screw that anchors the upper pivot jewel.
- Balance Complete: A term used when the balance wheel, hairspring, roller, and balance staff are combined as a pre-assembled unit, sometimes sold or swapped together with the Seiko Balance Complete and Cock
- Key Functions and Characteristics
- Timekeeping Regulation: It is a precisely weighted wheel that rotates back and forth (oscillates) at a constant, steady rate. [1, 2]
- The Hairspring Partnership: It works together with a tiny, coiled spiral spring known as the balance spring or hairspring. The hairspring provides the returning tension that pulls the wheel back toward its center. [1, 2, 3]
- Controlling the Ticking: As it swings, it interacts with the escapement (specifically the pallet fork) to let the gear train move forward in small, measured steps. Each swing creates a "tick" or "beat". [1, 2, 3]
- Beats Per Second: Most modern mechanical watches oscillate at a rate of 6 to 8 beats per second (21,600 to 28,800 vibrations per hour). [1]
- Portability: Unlike a wall clock's stationary pendulum, the balance wheel and hairspring form a compact harmonic oscillator that works in any position or motion on your wrist
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Poising the Balance Wheel
A poised balance wheel is a watch balance wheel with even weight distribution all the way around its circumference, which prevents positional timekeeping errors. [1]
What Is Poising?
- Definition: When a balance wheel is "in poise," its weight is balanced so that gravity does not pull one side down more than another when the watch is in different positions. [1, 2]
- The Problem: An unpoised wheel has a "heavy spot". This causes the watch to run fast or slow depending on whether it rests dial-up, dial-down, or on its side. [1, 2]
- Static vs. Dynamic Poising:
- Static Poising: The balance wheel and roller are placed on a special poising tool with ruby jaws to find where the heavy side settles at the bottom.
- Dynamic Poising: A more advanced method that tests the balance while it is running on a timegrapher across multiple vertical and horizontal positions. [1, 2, 3, 4, 5]
How It Is Done
- Testing: The balance pivots rest on parallel ruby jaws. A very light touch (such as a single hair) or a puff of air spins the wheel. If it stops repeatedly in the same spot, that side is too heavy. [1, 2, 3]
- Correction (Screwed Balance): Watchmakers adjust or file down timing screws, undercut the screws, or add tiny timing washers in pairs. [1, 2, 3]
- Correction (Screwless Balance): Material is carefully drilled or shaved from the underside of the rim or wheel itself
2. Removing the Winding and Escapement Parts
- 2a. Remove the Ratchet wheel: Unscrew and remove the ratchet wheel.
- A ratchet wheel is a circular gear with asymmetrical, saw-shaped teeth that allows motion in a single direction while blocking movement in the opposite direction. [1, 2]How It Works
- Unidirectional Motion: The wheel pairs with a pivoting, spring-loaded finger called a pawl (or click). [1]
- Forward Rotation: As the wheel turns forward, the pawl easily slides over the gentle slope of each tooth. [1]
- Backward Lock: If the wheel tries to reverse, the pawl catches against the steep, vertical edge of a tooth to lock the mechanism in place. [1]
Common Applications- Mechanical Watches: The ratchet wheel sits atop the mainspring barrel and winds the mainspring when you turn the crown, while a click prevents it from unwinding backward
- 2b. Remove the Crown wheel (Reverse Thread): Unscrew the crown wheel using a right-to-loosen (clockwise) and left-to-tighten rule, which is the opposite of normal screws.
- Don't forget to remove the metal shim
- 2c. Remove the Click and click spring: Remove the click and pick up the tiny spring underneath it.
- Its made up of the click screw, the click itself, and the click spring.
- The spring has one end that points up, and one end that points down.
3. Disassembling the Bridges and Gear Train
- Remove the Barrel bridge: Unscrew and lift off the barrel bridge.
- Its held with two screws
- 3a. Remove the main train wheel bridge and the small escape wheel bridge.
- Removing the Train wheel bridge
- It's the long bridge that goes over the centre of the movement.
- Its held in with 3 screws.
- Remove the escape wheel bridge.
- Its a baby bridge that lies over the escape wheel.
- Held with 1 screw
- Its job is to be the upper pivot for the escape wheel
- Remove the 4 Gear train wheels: Take out the wheels in order: center wheel, fourth wheel, third wheel, and escape wheel.
- remove the pallet fork
4. Keyless Works and Motion Works (Dial Side)
- Flip the movement: Turn the movement over to access the dial/plate side.
- remove the Setting lever/yoke spring: Remove the flat screw and the spring-loaded setting lever spring.
- It's spring loaded ... be careful when you remove as there is some tension
Motion works: Take out the minute wheel and the 2 intermediate wheels.- Yoke and yoke spring:
- Stabilize the high-tension yoke spring with a screwdriver, lift it out, and remove the yoke.
- don't let it fly away !!!
- remove the yoke
- The yoke is also called the "return bar"
remove the sliding clutch & clutch wheel.
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Lubrication
To oil a Seagull ST3600 (a clone of the ETA/Unitas 6497-2), follow standard mechanical pocket-watch lubrication practices, matching the exact oils and greases to the movement's load and speed. [1, 2, 3]
Discussions on the Watch Repair Talk Forum note that standard Swiss ETA 6497 technical and oil charts apply directly to the ST36xx series. [1]
Recommended Lubricants
- Light Oil (e.g., Moebus 9010 or equivalent): Use on fast-moving, low-torque parts like the escapement jewels, escape wheel pivots, and fourth wheel pivots. [1, 2]
- Medium-to-Heavy Oil (e.g., Moebus 90, HP-1300, or D5): Use on the center wheel, third wheel, and dial-side jewels. [1, 2]
- Grease (e.g., Moebus 9504 or HP-300): Use on high-friction sliding parts like the keyless works, sliding clutch wheel, winding stem, and mainspring barrel walls/arbor. [1, 2]
Step-by-Step Oiling Guide
1. The Mainspring Barrel
- Barrel Walls & Coils: Apply a very thin film of grease (such as HP-300 or Moebus 9504) around the interior wall of the barrel and lightly coat the mainspring coils to prevent stiction.
2. Gear Train (Train of Wheels)
- Center Wheel & Third Wheel: Place a tiny micro-droplet of medium/heavy oil (HP-1300 or D5) on the upper and lower pivots after the bridge is set. [1, 2, 3]
- Fourth Wheel: Apply lighter oil (such as Moebus 9010) to the fourth wheel pivots as it rotates faster. [1, 2]
- Rule: Never over-oil. A tiny droplet that covers about one-third to one-half the diameter of the oil sink is enough. Too much oil will bleed and stop the movement. [1]
3. Escapement
- Escape Wheel Pivots: Apply a micro-drop of light oil (Moebus 9010).
- Pallet Stones: Lightly grease or oil the tips of the pallet stones using a specialized grease like Moebus 9415 (or a tiny touch of light oil), letting capillary action form a microscopic film with the escape wheel teeth. Do not flood the pallet jewels. [1, 2, 3]
4. Balance Wheel
- Balance Pivots & Cap Jewels: Oil the upper and lower balance jewel/cap jewel assembly with a very small drop of light oil (Moebus 9010). Use an automatic oiler if available to keep the drop uniform. [1, 2]
5. Keyless Works (Dial Side)
- Winding Stem & Sliding Parts: Apply a thick grease (Moebus 9504) to the sliding clutch wheel, setting lever, yoke, and any sliding/friction points on the winding stem.
- Setting Lever Screw: Place a microscopic amount of 9504 grease into the setting lever screw hole before seating the screw
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