This Sinn 103 chronograph came in for a problem with the crown to be sorted, only a small job really but as you don’t see these very often and it’s such a gorgeous Bundeswher type chronograph it would be a sinn not to show it (geddit?)!
The problem was the crown had detached from the stem, not because the stem had broken or stripped but because the spring loaded section had come apart. This meant the watch couldn’t be wound or hacked to set the time.
Obviously the spring inside was missing and whilst a repair could be made the best solution would be to order a new crown. Or so I thought! I contacted Sinn and the UK agent to order one but heard nothing back, this went on for a while so I decided to do the next best thing and repair the original. A spring was harvested from a suitable springbar and cut to size.
The end of the crown ‘tube’ had to be crimped back over the hexagonal end that was still attached to the stem so as to grip the it correctly to enable winding, date and time setting. When the crown is screwed home the hexagon joining section slides away from each other and the crown then disengages from the stem and spins freely to enable it to be screwed home without forcing a fully wound mainspring. To do this accurately I used my Seitz jewelling tool fitted with a flat anvil and a lanterning tool (for tightening canon pinions). This tool allowed the tube to be creased extremely accurately and prevented to much force being used or crimping the tube to deeply which would render the crown useless.
Once the crown was crimped in six places it now held together properly and slid against the internal spring pressure so it can disengage when needed.
The crown and stem were refitted and it now works as it should, however there was one more problem and that was the day ring wasn’t advancing correctly or sitting centrally in the frame. As with most watches this means the dial and hands have to come off to access the components.
Once the back was off again the signed Valjoux 7760 handwinding movement can be seen.
The movement was taken out and all those hands and dial were removed….
….which left the calendar components ready to be inspected. The problem was the offset day ring had ridden on top of its jumper, so that was refitted correctly.
Dial and hands back on, a bit fiddly when you can’t find your Valjoux movement holder! Just the main chrono sweep to go back on now.
All done and ready for recasing.
What a beautiful watch, I’d love to have one in my collection to be honest!