Broken stop-lever

This week I have started my final quarter of watchmaking education at North Seattle College here in sunny Seattle.  The primary focus of this last few weeks are to focus on finishing up remaining projects and final practice for the AWCI CW21 exam in August. 

Today I worked on a Rolex 3035, which is the previous incarnation of the 3135 that is found in many modern men's watches.  The watch had stopped entirely and I had to figure out why.

In this situation it was fairly obvious as there was something directly blocking the balance rim, the stop lever (also known as the hack) had broken.  In the 3035 the stop lever rides on the set lever.  When you pull the stem out into the setting position the set lever pivots, pushing the stop lever up where it lightly contacts the balance rim stopping the watch.  This allows one to easily set the watch to the second when changing time.

The hook at the back of the lever in this watch has broken off and the part was sliding freely, blocking the balance regardless of the position of the stem.  Fitting a new part confirmed that the slot where it rides and the set lever and in good condition and the old one has most likely broken due to fatigue because of improper assembly.  With the part being replaced the mechanism is once again working as designed.

Broken!

The new part with the old, broken part