I bought an inexpensive Chinese manual wind wristwatch for my grandson. It is a skeleton style watch based on the communist Tongji movement.
Above, the watch looking pretty flashy in gold coloured finish. The gold plate wore off the band in just a few days to reveal a brass band tarnishing by the hour. The bezel is probably base metal and will corrode in no time.
Out of the box, it was a terrible timekeeper, and very sensitive to attitude, low amplitude and with really bad beat error of more than 5ms (the probable cause of the latter).
Regulation of isochronism and timing improved the watch, but it was difficult to get error within 30s/day.
Rumor is that these are shipped unoiled… so a dry movement would contribute to the problems.
Closer inspection shows that the plate jewels do not have an oil cup in them, they have a flat outer surface with no reservoir for oil other than within the jewelled pivot.
A thought was to oil the high speed wheels, balance, escapement palettes and impulse pin… but I had seen online discussion of how fragile the shock setting springs have proven.
Above is the balance cock removed, and the shock setting spring can be seen in the setting (capstone removed).
Well, the advice is correct. Even expecting it was easy to break these springs and taking great care, above shows the inevitable it seems broken shock spring. The material and conditioning renders a spring that lacks sufficient ductility to remove and replace it without it fracturing.
Interestingly, the top of the mating surfaces of the shock setting jewel and capstone are both flat, again no reservoir for oil.
So, is it worth trying to get a spring (probably impossible anyway).
Let’s pressure test it first.
Above, a 3bar pressure test sees bubbles pouring out of the case back and crown seals, even though freshly greased (they were dry). The substantial leak at the crown is from the case tube which was so loose in the case that it could be pulled out with tweezers (loose fit, no sign of sealant or adhesive) The metal surface against which the o-ring bears is very roughly machined, so little wonder that it leaks. I was refunded on the basis of gross water resistance failure.
So, there it is, a tray of bits… the Tongji communist watch, as much about ideology as Chinese culture.