Jaeger-LeCoultre Calibers 240–245 – Technical Overview from Document 1094_JLC (Pages 7–13)

Pages 7 through 13 of document 1094_JLC continue the comprehensive technical exploration of the Jaeger-LeCoultre Calibers 240 to 245, focusing on detailed component diagrams, assembly procedures, lubrication specifics, and regulation techniques. This section is crucial for watchmakers performing maintenance, overhaul, or repair on these classic manual-winding movements.

Detailed Component Breakdown

• Exploded views of the movement show each part’s placement, including bridges, gear train wheels, keyless works, mainspring barrel, escapement components, and calendar mechanism (where applicable).

• Special attention is given to the seconds hand assembly, differentiating between small seconds (Cal. 240) and central seconds (Cal. 241, 243, 245).

• The calendar module components for Calibers 242 and 244 are illustrated with the date disc, jumper spring, and driving finger clearly identified.

Assembly Instructions

• Pages outline the step-by-step order of assembly, emphasizing the proper seating of wheels and pinions to avoid gear misalignment and excessive wear.

• The installation of the keyless works (setting lever, yoke, sliding pinion, winding stem) is detailed to ensure smooth crown operation for winding and time/date setting.

• Special notes highlight the importance of precise date jumper spring tension and correct positioning of the date-driving wheel for reliable calendar function.

Lubrication Guidelines

• A comprehensive lubrication chart specifies oil grades and exact application points:

  • Escape wheel pivots and pallet stones receive light, high-quality synthetic oil (e.g., Moebius 9010).

  • Barrel arbor and teeth require heavier grease to reduce wear during winding.

  • Calendar mechanism pivots get minimal oil to prevent sluggishness.

  • Keyless works are lubricated sparingly to maintain smooth clutch engagement.

Regulation and Timing

• The recommended regulation parameters include:

  • Beat error below 0.8 milliseconds

  • Amplitude between 250° and 280° in dial-up position

  • Rate adjustment via fine index regulator on the balance cock

• Instructions detail how to monitor the seconds hand behavior (smooth sweep for central seconds, steady rotation for small seconds) and ensure proper functioning after assembly.

Servicing Tips and Common Issues

• Watchmakers are cautioned to verify free play in the gear train before final assembly to avoid premature wear.

• Ensuring the date changes crisply at midnight is a key test for calendar calibers; soft or delayed changes often indicate weak jumper springs or dirt in the mechanism.

• The importance of cleaning all components thoroughly is emphasized to prevent oil contamination and gear binding.

• Special attention is recommended for the setting lever spring and sliding pinion, which are prone to misalignment during reassembly.

Applications and Model Usage

• These calibers were widely used in a range of Jaeger-LeCoultre dress watches from the 1950s to the 1970s, including models with and without date and with varying seconds displays.

• Typical case sizes for these movements range from 34 mm to 37 mm, crafted in stainless steel, gold, and platinum.

• Their versatility made them popular among collectors and watch enthusiasts who appreciate classic mechanical watchmaking.

Conclusion

Pages 7 to 13 of document 1094_JLC provide essential, detailed information for the successful maintenance and repair of Jaeger-LeCoultre Calibers 240 through 245. The clear diagrams, lubrication schemes, and assembly instructions ensure that watchmakers can preserve the precision and longevity of these iconic manual-winding movements. These pages serve as an indispensable resource for anyone servicing or restoring JLC’s classic mid-century calibers, combining mechanical complexity with timeless elegance.