Jump to content
  • 0

Source of Large Positional Variation?


Question

I've just serviced a previously running Seagull ST36, as part of Level 2 of Mark's watch repair course.  Prior to servicing, the rate in all positions was between -6 and +6 s/d and was steady for each position.  After servicing, there is a large positional variation between dial-up and dial-down.  In addition, in one position the rate takes one of two distinct values.

Dial-up, the rate is about +30 s/d.  Dial-down, it starts at -10, but will eventually switch to +30.  I find that if I tap the movement with my finger in dial-down, it will immediately switch rates from -10 to +30.  In all other positions the rate is a steady +30 or so, and the amplitude in all cases is between 270 and 290.  Interestingly, when the rate switches from -10 to +30 the timegrapher shows the beat error changing from 0.8ms to 0.1, although I don't know if this is an artifact.

What could be the source of this behavior?  Could it be improper oiling of the balance jewels?  I've had difficulty getting them perfectly oiled as per Mark's instruction, even after several attempts.  I can see a circle of oil in the upper jewel, although the width is a bit below Mark's recommended 50%.  The lower jewel appears to be slightly over-oiled, with oil extending to the edges of the jewel for about half the circumference.

Link to post
Share on other sites

5 answers to this question

Recommended Posts

  • 0
8 minutes ago, Giannifive said:

I've just serviced a previously running Seagull ST36, as part of Level 2 of Mark's watch repair course.  Prior to servicing, the rate in all positions was between -6 and +6 s/d and was steady for each position.  After servicing, there is a large positional variation between dial-up and dial-down.  In addition, in one position the rate takes one of two distinct values.

Dial-up, the rate is about +30 s/d.  Dial-down, it starts at -10, but will eventually switch to +30.  I find that if I tap the movement with my finger in dial-down, it will immediately switch rates from -10 to +30.  In all other positions the rate is a steady +30 or so, and the amplitude in all cases is between 270 and 290.  Interestingly, when the rate switches from -10 to +30 the timegrapher shows the beat error changing from 0.8ms to 0.1, although I don't know if this is an artifact.

What could be the source of this behavior?  Could it be improper oiling of the balance jewels?  I've had difficulty getting them perfectly oiled as per Mark's instruction, even after several attempts.  I can see a circle of oil in the upper jewel, although the width is a bit below Mark's recommended 50%.  The lower jewel appears to be slightly over-oiled, with oil extending to the edges of the jewel for about half the circumference.

Magnetism could be the issue. But more likely some issue with a pivot. Tapping and the watch rate changes might be a pivot slipping back into the jewel. As well, you may have a sticky hairspring and the tap releases it. Is it magnetized or perhaps some oil on the hairspring. Have a close look or videotape in slowmo with your iPhone and have a look. 

Link to post
Share on other sites
  • 0

Thanks for the suggestions.  Demagnetizing didn't have an effect, so I cleaned the balance again.  I used One Dip this time instead of naphtha like I had been using, and that did the trick.  The hairspring must not have been fully clean.

Link to post
Share on other sites
  • 0
1 hour ago, Giannifive said:

Thanks for the suggestions.  Demagnetizing didn't have an effect, so I cleaned the balance again.  I used One Dip this time instead of naphtha like I had been using, and that did the trick.  The hairspring must not have been fully clean.

Good job. Amazing how a gummed up hairspring impacts positional error

Link to post
Share on other sites
  • 0
1 hour ago, Giannifive said:

I used One Dip this time instead of naphtha like I had been using, and that did the trick.  The hairspring must not have been fully clean.

just to be clear rinsing solved all your problems?

then are you really using naphtha or lighter fluid?

then also helpful if you give us a picture of your timing machine results because sometimes we can see things in the graphical display that you might not see.

Link to post
Share on other sites


  • Recently Browsing

    No registered users viewing this page.

  • Topics

  • Posts

    • I bought this for my new watch bench. It is nice but because of the way you work on a watch bench, the lamp is mounted on the same plane as your work space (this is higher than if it were a typical work bench).  As a result, the lamp cannot pivot upward enough to get optimal positions. So, what I had to do was design and print an short extender that pushes the fulcrum of the lamp away from the manufactured pivot point.  This allows me more range of motion. I am pretty happy with how it turned out.
    • This purchase must qualify:
    • Please keep us posted though. It's a beautiful clock and well worth a bit of time and effort to get it back to it's original glory. Good luck!
    • Did a bit more today on my Hettich. I also mucked around with practising on the top plate from the second Hettich that I bought. The calico wheel can leave marks and I am being gentle. I am certainly not pushing the plate into the wheel. I could easily stall the bench grinder that I am polishing on. I am wondering if Hettich started to use a lower grade of brass? I still cannot polish the brass to a mirror finish. On my Hettich (older) I have had to emery one of the posts that supports the movement and after 600 grit then 1500 grit, straight to Tripoli on my stitched wheel, then green on the calico wheel and the post is spotless. Absolutely gleams. post has a steel nut on the top of it that was rusty and affected by the battery acid. It is now polished as best as can be done and then I mucked around with a bit of heat and have changed the colour of the nut which looks quite good now. It was black originally. I have done several jobs now by hand where a having a lathe would have been so much quicker. Have to get rid of the Esprit first. Then I might have a chance.
×
×
  • Create New...