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August 30, 2011 at 6:31 pm #48088c.kellyParticipant
Been working on a Bulova 7AK wristwatch recently. Cleaned and oiled. replaced mainspring but with all that watch would still run and stop. Before I put hands on you could not keep it stopped. In any position you could stop balance but as soon as you removed pressure it would start right back up. With hands and cannon pinion it runs and stops. Hands were not touching dial and not hanging on each other. Last night was doing some more checking and found that if I tried to set watch counter clockwise that the sub second hand would stop and even move backward a bit. Took dial off again and without hands I decided that setting gears seemed way too tight. Put another cannon pinion on and eveything loosened right up. Watch no longer stops when set counter clockwise and as of now hasn’t stopped at all. I’m guessing maybe someone before me put wrong pinion on it. Could sure tell difference when i put the one I had on it. Setting was much easier. I’m now trying to work out in my mind exactly why a tight cannon pinion would stop watch. I can see it when setting but in normal operation it seems to me as if pinion is supposed to be held by shaft it is placed on by friction? Why would too tight stop watch? In this particular watch I know balance is good, hairspring looks fine under 16 power.
I am still trying to learn how to figure out issues of watches that aren’t running and get them going again and would appreciate any thoughts.September 6, 2011 at 10:56 am #50780Bob TascioneModerator
Good call c_kelly,
Your cannon pinion may have been the wrong one or it may have been corroded or possibly damaged in the past by an improperly performed adjustment. I believe the problem was either the meshing between the cannon pinion and minute wheel teeth and/or the fit between the hour pipe and the cannon pinion. The mesh with the minute wheel must be smooth with absolutely no catching. If the teeth were corroded or damaged then that may have been the problem. If the cannon had some kind of rust or corrosion or was distorted or a burr thrown up while trying to tighten the cannon pinion then it may have resulted in too tight a fit or catching with the hour wheel tube. This fit must be a close but smooth one with no resistance between the two surfaces. Any of these problems will cause undue dragging in the motion train which could stop a watch.
Hope this helps C_kelly
BobSeptember 17, 2011 at 9:04 pm #50781c.kellyParticipant
Thanks for your reply. Watch is still going strong. Guy at work has just asked me to take a look at some of his watches. One was a Caravelle pocket watch that was slipping badly when wound. Took stem out, put it back and tightened up screw and that issue went away. Other one is Elgin 12 size with exact same problem. wind it and it sllips. Other thing apparant is staining and bit of rust on winding gears. Told him would be good idea to replace those gears which I can easily do. Have not taken this one apart yet as it is also very dirty. Also looks as if whoever worked on it last was a bit off his game. Hands were installed wrong so that when minute hand is at 12 the hour hand is between hours. Another easy fix. Will try to get donor movement on ebay to replace stained rusty parts. He was so happy with caravelle when I took it back to him Friday that he said he was going to bring me another that he got for graduation present years ago. Am having a lot of fun and actually made a dollar or two this week. I will probaly post again when I get into the Elgin which is a 384 caliber if I remember right.
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