Training Background
In 2017, while we were carrying out repair work on the Terra Ring smartwatch, we conducted a technical training session using the rangefinder mechanism of a Leica M6.
This is one of the training projects we conduct on an ongoing basis. Its main purpose is to help engineers understand the basic principles of precision mechanical structures and develop practical skills in disassembling and reassembling precision mechanisms.
How the Rangefinder Works
The Leica M6 uses a mechanically coupled rangefinder. As the lens focusing ring turns, the lens’s control cam transfers the focus movement to the camera’s internal linkage. This moves the secondary rangefinder image in the central focusing area of the viewfinder. When the two images align, the rangefinder indicates that the focus position is correct. leica-camera.com
With continued use, the M6 rangefinder mechanism can develop vertical misalignment, leaving the two images unable to coincide fully. This deviation can gradually accumulate over time. Inspecting and correcting the image alignment was the central focus of this training.
*The image above is for illustrative purposes only. After a period of use, the two rangefinder images may become slightly misaligned vertically, making it difficult to judge visually whether the subject is accurately in focus.
Training Content and Key Procedures
The training covered basic Leica M6 top-cover removal and reassembly, how rangefinder misalignment can occur, and how to inspect and correct it. After adjustment, the engineers checked the alignment of the superimposed images and then checked the rangefinder’s focusing accuracy.
Careful preparation is essential when working with precision mechanisms. Before disassembly, important component positions should be marked and key structural details recorded. Removed parts should be arranged in the order in which they were taken out. Reassembly should then follow the reverse order, restoring the position and relationship of each component step by step.
Applying the Training to the Terra Ring Repair Project
The Terra Ring smartwatch has a special sensor beneath its rotating bezel. The sensor records the number of gear teeth as the bezel is turned. Users can use this function to make adjustments, such as operating controls similar to up and down buttons, and to play games.
The sensor is very small and is difficult to see with the naked eye. If the rotating bezel is not reassembled in the correct position relative to the sensor, the sensor may fail to detect the movement. During the repair project, we found that engineers needed more practice positioning the bezel and assembling it in coordination with the sensor.
The Leica M6 training gave engineers a practical way to study the positioning, structural relationships, and reassembly of precision mechanical components. After the training, their ability to position the Terra Ring’s rotating bezel and assemble it in coordination with the gear-tooth sensor improved noticeably.
Supporting Local Photography Clubs
The precision disassembly and reassembly experience gained through this training has also supported our work with local photography clubs and provided a technical foundation for camera maintenance.