Adjusting pallet forks

[Shane]

I have an odd situation and a follow up question.  I have made several searches and read several post that really didn't pertain to my issue.

I am working on a previously mentioned AS 976 and find the impulse jewel seems to be to wide to fit between the pallet fork horns without help.  Since the impulse jewel is unlikely to have grown, I can only imagine that the fork has been damaged or parts have been mismatched.  As all the pieces came as an assembly (in very bad condition) from a jumbled box of movements, either is plausible.  If the fork is bent, I feel confident that I have not mishandled it.

my question is, has anyone adjusted the horns of a pallet fork?  At this scale, I have no way of determining whether or not they are now parallel and realize that if they are now, they wouldn't be after adjusting.  I can't see why that would be important anyway.  I also have no way of accurately measuring the impulse jewel without removing it first.

How would you proceed?

I'm sorry.

After posting I went back to the beach to tinker with it again and found the root cause of my problem.

I removed the fork for a better look and found nothing worth noting.  So I dropped the balance back in without the fork and found the same problem.  It wasn't an interference between the impulse jewel and the fork.  It was that the balance screw that swung the largest circle was hitting a nick in the mainplate.  It just happened that it was timed to coincide with the jewel entering and exciting the fork.

I gently scraped the plate, removing the nick, cleaned up the crumbs and reassemble.  It came back to life.

That being said, has anyone ever ajusted the width of a pallet fork?

Shane 

[Shane]

I just got this running the other day but I have family visiting this week and until this morning, have been unable to spend much more time than winding it in the mornings.

Ok, so it is running with acceptable amplitude... face down.  Drops totally dead face up.  The hairspring looks flat, even and reasonably concentric while running (just one coil is uneven but I can't see that as causing my problem) and I see nothing interfering.  I have taken the balance out several times and can see nothing that could be making contact.  I removed the pallet fork again and sure enough the balance still stops face up.  Just to be sure, I redressed the area that it was hanging up on before, that didn't help at all.  There is no perceivable end shake so my first thought was that the staff couldn't be rubbing on the under side of the jewel when inverted but the position the wheel stops at when inverted does not seem consistent, suggesting the interference is.  That being said, I will pull the balance and see if there is any possible space between the jewel and the end stone (there is no shock system).  If I can move the jewel closer to the end stone that might help.  If the end stone moves also that shouldn't help.

Any thoughts?  I will be going out with the family for most of the day but I'll try to give this more thought myself.

Have a good day yourselves.

Shane 

[Nucejoe]

Have you removed end stones to clean and inspect?

[Shane]

Yes, removed and cleaned.  I was planning on removing them again upon my return this evening.  I will inspect more thoroughly at that time.

Shane 

[Shane]

 

5 hours ago, Nucejoe said:

Have you removed end stones to clean and inspect?

I've taken both end stones off and they look fine. Both are clean with a crystal clear drop of 941 covering about half of their surfaces.

 

It looks as if I may be able to recess the hole jewel a very few thousands of an inch deeper. That might be enough. What are the odds of me pushing the jewel just past the top surface of the balance cock and then pushing it back down against it's domed side with a tool larger than the hole (so the cock and jewel wind up being tangent to each other) without cracking it?

 

Shane 

Edited August 27, 2022 by Shane

[Nucejoe]

 Good idea, and putting penetraing oil around the jewel reduces the risk, though I don't think there is much of a risk, I done lots of such jewel adjustment and don't recal breaking one. 

Good luck