Since the revival of the mechanical watch industry during the mid 1980s enthusiasts have become ever more absorbed by mechanical chronometry, taking pleasure in comparing the performance of new and old models alike. The very finest of detail can create a perceived or real difference in feel when wearing a favourite timepiece. But there are some fundamental strength requirements which all watches, mechanical or digital, must withstand and are routinely verified by producers as part of their quality-control process.
A leading Swiss watch producer needed to evaluate the torque characteristics of a rotating timer bezel on a dive watch. The minute-clicking bezel is designed to be rotated on one side, to prevent accidental adjustment when underwater, and able to be set by the diver when wearing gloves.
Bezels operate by means of a ratchet mechanism and, with intensive use, the small metal spring can become worn, resulting in a slightly loose bezel, or one that turns in both directions. The test method required the measurement of the torque to initiate rotation of the bezel and keep it turning over a specified number of degrees.
Mecmesin designed a lower fixture out of Delrin to match the exact geometry of the body case and hold it in place. An upper fixture was produced to locate snugly around the bezel. The fixtures were connected to Mecmesin’s precision torque test system fitted with a static torque sensor and controlled by Emperor Torque software. Data was displayed graphically and the peak torque, in N.cm, over the specified angular rotation was automatically calculated. The results and graph were exported to a PDF report to produce full traceability of the test.
The design engineers in Switzerland were then able to evaluate the graph characteristics against their specifications for positive engagement and feedback in incremental adjustment, to optimise the quality feel and functional performance of the bezel.
Other related torque tests include testing watch stepper motors, winders, mechanical drives, gears, plus friction of watch parts including watch hands and other micro-mechanical components.
Helixa-i precision torque tester
Torque cell matched to the expected values
Custom fixtures to hold the watch casing and to engage and turn the bezel