Pallet fork problems?

[Stevelp]

Hello all, I hope this post finds you all well!  I’ve been working on a small ladies watch with an FHF 60 movement.  I’ve cleaned and oiled the movement and replaced the balance assembly due to a bent pivot.  With the watch completely assembled, amplitude is almost non existent.  With the pallet fork removed, the gear train moves very well, with that slight reverse in motion evident in the escape wheel.  With the balance installed without the pallet fork , the wheel spins freely for quite some time, so no issue there either.  So at this point I believe I my loosing power through the pallet.  When I move the pallet back and for with watch wound I don’t get a good snap back and forth to the banking pins.    I don’t have much experience in escapement testing and adjusting.  My first thought is if the lock is to deep.  I thought it seemed ok, but would like to know what others with more knowledge on the subject think.  It’s hard to get pictures of both stones as one is quite hidden and a picture from the front through the inspection holes doesn’t show it very well.  Both stones are about the depth in the picture provided.  If this looks ok, any other tests that would be recommended?  I apologize if the picture quality isn’t great.

[Klassiker]

The lock does look quite heavy, but I don't think it is the cause of your problem. If the fork is not snapping back and forth, then check the pallet fork pivots and holes are clean and smooth, and check the end-shake.

If you are sure the fork is moving freely, then focus on what you changed. Maybe there is interference between the guard pin and your new balance, or between the impulse jewel and the fork horns.

[watchweasol]

Hi. Follow what klassiker said but also check the balance is free running. Take the fork out (remove power first). And fil balance and give it a puff of air,  does it swing ok for up to 25 secs freely.   Also check its pivots if it’s had a knock one of the levels may be broken or cracked.

[VWatchie]

I agree with @Klassiker. Also, make sure that you do not oil the fork pivots. Have you oiled the pallet stone impulse surfaces? The type of oil that you use and how much can make a dramatic difference. Even dry impulse surfaces make a dramatic difference.

[Nucejoe]

No study of the cosmos, a test for the fork and balance assembly is to put  just the fork/cock  and balance/cock on the mainplate and observe, this will also provide wider angle of side view to see fork/ roller engagement.

 

 

[nickelsilver]

With just the fork installed, no power, it should move easily with a light puff of air. Then, as you have already checked the balance freedom, check with fork in no power (without escape wheel would be best).

 

As said, no oil on the pivots, peg the jewels, no oil on the roller jewel (!), make sure the fork slot that interacts with the jewel is dead clean, also have a look at the roller jewel, they sometimes are grimy even after cleaning. While the lock does look a bit heavy, there's a whole checklist of things to examine before considering moving a/both stones or adjusting the bankings.

[Stevelp]

Thanks everyone for your input!  So I removed and re-cleaned the pallet fork and its pivot jewels.  I don't oil fork pivots so there was no concern there.  As far as lubricating the pallet stones I use Moebius 9415 on the exit stone.  I've seen it applied to only the exit stone and also both stones as well.  Is one more acceptable than the other?  After cleaning again, the action of the fork seemed to be better, but with the balance installed it would still hardly run.  The only balance ran in horizontal positions, but not in vertical positions, so I decided to try the old balance to see if things would work better, and sure enough it did!  I swapped over the roller table to the new balance and it ran much better.  I will do some more comparison to see what the difference might be between the two tables causing the issue and post again shortly.  

[Jon]

From the photo, the pallet fork arbor jewel looks massively worn to me creating a big side-shake and a much deeper and shallower lock in vertical positions because of the excessive side shake reducing your amplitude because of that deep lock.  A shallow lock may cause mislocking

There should be no discernable or visible side shake, so if you give the pallet a wiggle and see the arbor visibly moving sideways, that is far from acceptable. There should be about 0.01 mm to 0.015 mm side shake of the pallet fork.

Edited September 7, 2023 by Jon

[Stevelp]

Thank you Jon for the excellent advice!  Ill have a good look under the microscope to confirm.