ETA 6497 Disassembly

For the sake of full transparency the pictures presented in this post are of a Seagull ST3600 swan neck movement.

The Seagull ST3600 (or ST36) is the Chinese clone of the ETA/UNITAS 6497. 

We first list some of the key parts composing the ETA 6497:

  1. Hour wheel (31.046)
  2. Driver cannon pinion (31.080)
  3. Balance complete with bridge and ETACHRON system
  4. Pallet bridge, jewelled (10.057.07)
  5. Pallet fork (40.010)
  6. Crown wheel
    1. Screw for crown wheel (31.023.01)
    2. Crown wheel (31.023)
    3. Crown wheel ring (81.067)
  7. Ratchet wheel
    1. Screw for ratchet wheel (31.020.01)
    2. Ratchet wheel (31.020)
  8. Click (51.120)
  9. Click spring (61.080)
  10. Centre wheel (30.015)
  11. Barrel (20.010)
  12. Second wheel, with long lower pivot (30.027.13)
  13. Third wheel (30.025)
  14. Escape wheel (30.040)

Top-movement Disassembly:

Starting to work on the top of the movement we remove the hour wheel and cannon pinion.

Bottom-movement Disassembly:

When disassembling the back, we start by taking out the most sensitive component, the balance bridge (housing the balance spring). When unscrewing the screw for the balance bridge, make sure there is no force on the main spring. We recommend using a balance cock support tool to hold the bridge (allowing the spring to drop freely).

With the balance bridge out of the way, the pallet bridge is left exposed. Start by removing the two screws holding the pallet bridge in place, and the pallet bridge itself (that in turn holds the pallet fork). Finally remove the pallet fork.

To disassemble the crown wheel, turn the crown wheel screw clockwise to free the wheel, and do not forget to remove the crown wheel ring afterwards. Disassemble the ratchet wheel next, by turning the ratchet wheel screw clockwise and freeing the wheel.

To disassemble the click, start by removing the click screw, then free the click, and finally the click spring underneath.

Once the crown wheel, ratchet wheel, and click have been disassembled, unscrew and remove the barrel bridge. Unscrew and remove the train wheel bridge next.

Once the barrel bridge and train wheel bridge have been removed, you can complete your disassembly by removing the centre wheel, barrel, second wheel, third wheel, and finally escape wheel.

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