How to shorten the Balance Fork on my balance for the Seth Thomas repair

Probox

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Hi. I was cleaning and reassembling this Seth Thomas clock and when I was using the lathe to polish the pivots I had a little mishap with the fork arm. It got bent. I simply straightened it and reassembled. Now the forks are touching the balance pin thus stopping the balance from freely rotating. Any ideas on how I can shorten this? It's the distill end of one of the forks only that touches the balance wheel stake. 20210622_193055.jpg 20210622_193102.jpg 20210622_193112.jpg 20210622_193119.jpg
 

Probox

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The adjustment screw on the top affects the pallets and the fork. Can you adjust it so the pins pass?
Hi Wow, yes, I thought of that as there is a bridge for adjustment but I was a little worried I might mess up the proper pallet EW depthing so I didn't want to mess with that! I may have to consider it though.
 

Probox

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With this type of escapement a proper beat adjustment usually fixes the issue.
Hi. I do have the balance wheel pin centered between the forks when it is all at rest. I assume that's what you mean by in beat? Or is there something I am missing?
 

wow

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What Rough is referring to is the even ticks which is adjusted by removing the little pin at the end of the balance spring and adjusting the spring so the ticks are even and the clock is in beat. With my suggestion, insert a small screwdriver through the escape wheel so it can’t turn and then loosen the screw slightly moving the tab a tiny bit away from the escape wheel. Then tighten it and carefully check it. The fork will also move when you move the pallets.
 

Probox

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What Rough is referring to is the even ticks which is adjusted by removing the little pin at the end of the balance spring and adjusting the spring so the ticks are even and the clock is in beat. With my suggestion, insert a small screwdriver through the escape wheel so it can’t turn and then loosen the screw slightly moving the tab a tiny bit away from the escape wheel. Then tighten it and carefully check it. The fork will also move when you move the pallets.
Okay, I'll give that a try but it will have to be just an every so soft adjustment so that the pallets are still interacting correctly with the EW.
 

Simon Holt

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I do have the balance wheel pin centered between the forks when it is all at rest.
I was waiting for someone else to comment on this assumption. I have very little experience with this type of escapement, but I wondered whether 'at rest' is the same as being 'exactly between ticks'. Maybe it comes to rest after being pushed in one direction by the escape wheel, and is therefore would not be centered.

Feel free to ignore this if I'm talking rubbish!

Simon
 
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wow

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Okay, I'll give that a try but it will have to be just an every so soft adjustment so that the pallets are still interacting correctly with the EW.
Yes. After adjusting, hold the EW with your finger and rock the pallets to be sure they escape properly and the EW does not spin freely. Tiny adjustments.
 

Probox

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I was waiting for someone else to comment on this assumption. I have very little experience with this type of escapement, but I wondered whether 'at rest' is the same as being 'exactly between ticks'. Maybe it comes to rest after being pushed in one direction by the escape wheel, and is therefore would not be centered.

Feel free to ignore this if I'm talking rubbish!

Simon
Yes, Simon, my assumption as well. Could be wrong. For example is there a difference if there is power to the EW compared to when no power to the EW? I have the mainspring unwound with no power to the EW and I centered the balance pin within the center of the forks. I'm not sure.
 

Simon Holt

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Yes, Simon, my assumption as well. Could be wrong. For example is there a difference if there is power to the EW compared to when no power to the EW? I have the mainspring unwound with no power to the EW and I centered the balance pin within the center of the forks. I'm not sure.
If you watch the action of the wheel and fork when the clock is running, you will see how much 'overswing' there is. In other words, at one end of the swing the pin will exit the fork before the wheel reverses direction. Look to see how far the pin gets beyond the fork in each direction. If the distance is the same in both directions, then that would be a visual indication that the clock is in beat. You should also be able to tell by how it sounds, or you could use a smartphone application to display the beat (I use Clock Tuner on an Android phone).

Simon
 

kdf

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Aug 26, 2011
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I'm not fammiliar with this clock, but this type of fork is common in alarm clocks. In most of these fork is not straight, it has courve in the midlle - this courve is there to adjust fork lenght. If I understand well you simply straightened it so it's clear that fork became too long... Adjust it carefuly by bending it in the midle and do not touch the bridge, it is for adjusting anchor and not the fork.

DPP_0001.JPG DPP_0002.JPG
 
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wow

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I'm not fammiliar with this clock, but these type of escapements are common in alarm clocks. In most of these fork is not straight, it has courve in the midlle - this courve is there to adjust fork lenght. If I understand well you simply straightened it so it's clear that fork became too long... Adjust it carefuly by bending it in the midle and do not touch the bridge, it is for adjusting anchor and not the fork.

View attachment 660207 View attachment 660208
That’s it. I didn’t read well. Good catch, KDF.
 

RJSoftware

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The balance wheel is put into "beat" by adjusting thehairspring collet. The hairspring collet is friction fit to the balance wheel arbor. To adjus stick blade of small flat head screw driver in the slot of hairspring collet, hold blade stationary then turn balance whee in desired direction. Even beat is established when balance wheel impulse pin travels equal amounts on both sides of imaginary line between balance arbor and fork arbor.

Adjusting the hairspring terminal location is how timing fast/slow is established in the rough. The ideal termination lands the regulator dead center. Fine tuning with regulator a few degrees off center is acceptable, however, a sign of poor regulation is one set to far end +/-. When you see this you got other issues most likely.

Try to re-establish original hairspring termination. Look under high power loop for tell tale bends.

The whole issue was when you flattened out the curve. You might still have beat. As to the termination, someone may have spent considerable time and effort in a process called "vibrating the hairsring". It is a long laborous process of selecting, fitting and regulating with a special and expensive tool that allows clock/watchmaker to compare and tune the exact length and termination point.

Not only that, but there are no more manufacturing of the old style clock hairsprings. Modern hairsprings are much different and unusable as they are more stiff and require many extra loops to work. Extra loops cause the hairspring body to be too large and wont fit regulator.

Once you restore the fork curves, two needle nose pliers, so that fork tongs pass by balance arbor, restore original hs pin termination, you should be ok.

If it's off beat be careful, take your time inserting small blade in collet slot, it's easy to slip and bend up hairspring.

Adjust beat with fully assembled movement in hand. What I do. hold movement in left hand. With left finger or thumb, whichever easier, roll balance wheel around till hairspring collet slot is seen. Hold small thin blade screw driver right hand finger & thumb, test fit, a good fit will have bite. Rest right wrist against movement, now holding both hands in front of face, like sandwich. Dont push screwdriver hard, the collet friction fit will slide easy enough. Roll the balance wheel a few degrees while collet stays stationary. Test results.

By resting hands against movement I reduce errant movement, slips etc. I even form a bridge by holding left hand to face. 3 contact points. But the right magnification and lighting comes into play. Holding left hand against face holding movement with both hands for me prevents errant movement. For others resting arms on table while holding movement both hands. Vision becomes the issue.

Look for balance impulse pin to travel equal distances on each side of imaginary line between balance arbor and fork arbor.

Also, the. 3 positions on fork end. Center slot and two side slots (one each side) they ate for over banking which happens on clocks too. They prevent balance pin from crossing over to wrong side, lock out. So test that when you adjust length.
 
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Uhralt

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I'm not fammiliar with this clock, but this type of fork is common in alarm clocks. In most of these fork is not straight, it has courve in the midlle - this courve is there to adjust fork lenght. If I understand well you simply straightened it so it's clear that fork became too long... Adjust it carefuly by bending it in the midle and do not touch the bridge, it is for adjusting anchor and not the fork.

View attachment 660207 View attachment 660208
Exactly!

Uhralt
 

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