Omega 420

[Jim]

Hi its been a while since I have posted   I have run into an interesting problem while servicing an Omega 420 movement     I will attach a photo   I fully serviced the movement  very clean now the photo was a before shot.   No broken pivots no cracked jewels.  But when I leave the screw that I have the blue arrow pointing to loose the watch runs  if I tighten the screw it stops.  No other screws seem to make any difference.  I have checked end-shake on all the gears.  while the screw is loose the watch will run all the way down.  I did notice that in stem down position the watch runs -100 spd  slow  dial up or dial down its fine  and long as the screw is not tightened?     All suggestions welcome.

Sincerely

 

Jim

 

 

[oldhippy]

Have you checked to see if the plate has been bent. Make sure the jewels both ends are clean, the same with the pivots. When you have the plate screwed down do you still have good end shake? Is it the right screw. Is the jewels seated correctly.

[Jim]

yes I have checked end shake and the jewels   with the screw tightened   every thing is very clean  the plate doesn't  appear to be bent  Its the large plate if it was machined improperly the watch would have never worked.    I am thinking one of the pivot ends may be slightly deformed I only looked at them under a loop    guess I need to look at each one under my microscope.

Thank you for your thoughts

 

Sincerely,

Jim

 

[oldhippy]

As you have a microscope that would be the next best move.

[Geo]

Take it apart and put only one wheel in at a time to see if you find a tight one.  Doing this with only one wheel will hopefully find the bad one.  Do this procedure with each wheel in the train, and rember to tighten the plates fully before testing how well each wheel spins.

If you don't find a single tight wheel, keep adding one extra wheel, tightening the plates every time intill yo have them all fitted, at some point along the the line you will probably find the offending combination that causes it to go tight.

[Jim]

Great advise Geo    I think the tight one is the double wheel that connects the train to the second hand.  I will try that one first alone.   I am thinking one might be slightly bent  because each wheel by itself seems loose even when I tighten the screw.   But the train wont spin freely even with the pallet fork removed once the screw is tightened fully  1/2 turn and it spins fine      I think that is why the watch was put away so many years ago.    The double wheel is a pain to get in place  lol 

 

Thank you sincerely ,

Jim