Servicing a Dreadnought Automatic: Restoring Precision to the SW200-1
This week, we were pleased to welcome a robust Dreadnought automatic watch to our workshop in Lewes for a full service and repair. Known for their utilitarian design and “tank-like” build quality, these timepieces are designed for endurance. However, even the toughest tool watches require regular maintenance to ensure long-term reliability.
While the watch was in working order upon arrival, the owner noted that it was not keeping time correctly. This is a classic indicator that the oils inside have dried or degraded and that specific components within the movement are struggling to operate efficiently. A full service was required to get this heavy-duty diver back to keeping precise time.
Disassembly and Diagnosis: Inside the Sellita SW200-1
The Dreadnought is powered by the popular and reliable Sellita SW200-1 automatic movement. This 26-jewel calibre is renowned for its robust nature and offers excellent performance when maintained correctly, making it a perfect match for a watch built to withstand harsh environments.
The repair was carried out here in our fully-equipped, on-site workshop in Lewes by BHI Accredited Watchmaker, Dan Stent.
Upon initial inspection and full disassembly of the movement, Dan diagnosed the core issues causing the poor timekeeping:
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Weak Mainspring: The original mainspring had lost its elasticity over time. As the power source of the watch, a tired mainspring is unable to deliver the consistent, strong torque required for stable amplitude and optimal timekeeping. A new mainspring was fitted into the barrel to restore full energy transmission.
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Worn Reversers: The reversing wheels—key components in the automatic winding module—were worn out. These wheels are responsible for converting the bi-directional rotation of the rotor into a single-direction force to wind the mainspring. When worn, the watch fails to build up a power reserve efficiently while being worn. These were replaced to ensure the automatic winding system functions smoothly.
The Service Process: Precision and Attention to Detail
The entire Sellita SW200-1 movement was fully stripped down into its individual components.
All parts were meticulously inspected for wear and then thoroughly cleaned using a multi-stage process in our specialist cleaning machine. This ensures every component is free of old, dried-up oils, dirt, and microscopic debris that can dramatically impact a watch’s performance—often the primary cause of a watch “working but not keeping time.”
Once the parts were immaculate and dry, reassembly commenced. Dan meticulously rebuilt the movement, carefully installing the new mainspring and reversers. Crucially, all lubrication was applied strictly according to the official Sellita technical documents, ensuring the correct oils and greases were used at every friction point to minimise wear and maximise efficiency.
Final Stages: Testing and Quality Control
With the newly serviced movement reassembled and back in the case, the Dreadnought underwent our rigorous final testing phase:
- Timekeeping: The watch was checked on our Timegrapher to ensure it was running to precise factory tolerances. The new mainspring ensured excellent amplitude, and the beat error was corrected.
- Automatic Winding: The efficiency of the new reversers was tested, confirming that the rotor now winds the watch reliably and smoothly.
- Power Reserve: The full power reserve was confirmed, ensuring the watch now holds its charge for the maximum duration.
This Dreadnought automatic is now fully restored and functioning at peak performance. It is once again the reliable instrument it was designed to be, ready for many more years of daily wear. Regular servicing is vital for any automatic movement, and we were delighted to bring this impressive timepiece back up to standard.
Need Your Watch Serviced or Repaired?
Take advantage of our Royal Mail Special Delivery FREEPOST service for a secure and hassle-free experience. Your watch is fully insured for up to £20,000 throughout its entire journey, from the moment it leaves your hands until it’s safely returned to you. Trust our expert watchmakers to restore your timepiece with precision and care.