Runs Great in all Positions EXCEPT DIAL DOWN

[fourtimes4]

I resently serviced an Illinois Bunn Special it is a type III m#14 from 1928. My baseline prior to service was amplitude 210 gaining 35 seconds per day BE 5.2. During my inspection found the lower balance jewel was cracked so I replaced it. Once service was complete my dial down amplitude was 190 to 202 losing 500 seconds a day corrected BE .09. Now flip it over to dial up & I’m hitting 320 amplitude, gaining  52 spd with a BE .03. All other position relatively similar readings. I didn’t see any pivot damage to the lower pivot on the balance staff. Pallet fork and balance seem to have good end shake. 

[JohnR725]

1 minute ago, fourtimes4 said:

lower balance jewel was cracked so I replaced it

the replacement jewel are you sure it's exactly the same as whatever the original was? Like is the pivots size exactly what it's supposed to be? Then visually if you look at the amplitude and not rely on the timing machine when it's running at 300 and something does visually the balance wheel look like it's really running that that?

oh and other minor little thing your lift angle is probably not 52°.

oh another thing you want to look at is the hairspring regulator pins how close together are they. The farther apart they are and they're not supposed to be there supposed to be as close as you can get them without actually grabbing the hairspring for an over coil. But when you have amplitude changes lower amplitude in particular it watch will go slower because your regulator pins are too far apart. Although you really do need to fix the amplitude issues but still the regulator pins will really amplify this problem

[Nucejoe]

 The magnification you have might not show you scratches on lower pivot.

I  would  polish the lower pivot ?  or both. 

I also make sure roller table is not rubbing on fork .

 

Edited January 29, 2024 by Nucejoe

[TimeWerks]

Adding to the prior suggestions, make sure the safety roller is not rubbing against the plate, or (as Nucejoe mentioned) the roller table isn't rubbing against the pallet.  

When you replaced the lower jewel, the depthing may have changed which would impact the divisions.  Also If the pivot hole is larger than the prior jewel, the pivot could be riding lower down than it was before.  

The last balance staff I replaced, I used the hamilton staff specified for that watch, but the pivot holes of the jewels were not correct size.

[JohnR725]

5 minutes ago, TimeWerks said:

The last balance staff I replaced, I used the hamilton staff specified for that watch, but the pivot holes of the jewels were not correct size.

one of the things you have to be careful with American pocket watch staffs and jewels are. Despite having a parts book that says a exact specific staff and perhaps exact specific jewel goes in that watch you oftentimes find variations. Elgin intended to be better at documenting their variations so you can have one staff number that's actually see the three or four different staffs by GNU style and old-style slaves physical differences in the staff itself and then each staff couldn't have up to five different pivots sizes. Which is why of course you always need to measure before the staff came out in the staff that's going and just to make sure that they agree

then sometimes the aftermarket parts can be a different size. For instance the Hamilton 992B only has one balance staff but I've seen a replacement staff for it physically would not go in and it's a friction staff because it was too big.

so yes American pocket watch parts is not an exact science because there can be so much variation. But you can have a parts book that specifies a very exact part because maybe the book was written the early in the life of the watch and the watch was made for number of years.

 

[fourtimes4]

I did measure the lower pivot on my JKA micrometer and after several times it consistently came out as 11 so I that size for the replacement from Clean Time Jewels on eBay which I have had good success with his product. I will look at all areas mentioned above. I appreciate the helpful feedback. I have always assumed the lift angle is incorrectly set but I mainly use it for determining before I touch it and after to see if I’m improving the performance or not. 

[nevenbekriev]

There are two most probable reasons for wahat You describe:

1: Something wrong with pivots/stones

2: Hairspring.

To understand what is the problem, I will advice to take off the hairspring and to put on the pate the balance with it's cock. The lever must be out. Turn the balance and observe how it rotates free. When everything is OK, in horizontal positions it will rotate for long time and will slow gradually, and will turn with lo speed for a long time. Observe how it behaves in both horizontal positions and if there is difference between both position. If there is significant difference, search for the reason: Does the pivot head look normal (rounded, not flat and even riveted)?  Is the pivot not bent? The pivot head must rest on the cap jevel in a manner that if the cap lewel was not there, the pivot would get in the hole stone at least 0.05mm deeper.

If or when the balance slow  free rotation is/gets to normal, then the hairspring comes to turn. Of course You know that it musd be centered, level and not to touch anywhere, but one has to know where to look. In DD position, it may rubb in the balance arms. Thow in rest position it may not touch them, when balance is rotated, the things may change. In DU position, the spring may touch the studd bottom and the regulator pins, and the overcoil - the cock.

[fourtimes4]

OK I may have discovered my issue. The jewel setting that was cracked has an overall thickness of .49 mm the replacement measures .48 mm. Excuse me

if my terminology is incorrect. The shoulder of the setting that rest on the ledge of the mainplate is thinner. The original setting shoulder is .29 mm and the replacement is 

only .14 mm. or am I off base. I had an exact hole jewel replacement with the exception the hole was a .12mm. I set this one and it caused the watch to knock when in the 

dial down position. Would the cure be to swap the jewels from the settings.

[JohnR725]

2 hours ago, fourtimes4 said:

Would the cure be to swap the jewels from the settings.

it would be perhaps if it was really that simple. if it's an original jewel there typically burnished in. Removing a burnished in jewel and replacing it with another one can be done but it can be tricky. It's a modern reproduction it's probably pressed in removing that is relatively easy.

 

 

[nevenbekriev]

5 hours ago, fourtimes4 said:

OK I may have discovered my issue. The jewel setting that was cracked has an overall thickness of .49 mm the replacement measures .48 mm. Excuse me

if my terminology is incorrect. The shoulder of the setting that rest on the ledge of the mainplate is thinner. The original setting shoulder is .29 mm and the replacement is 

only .14 mm. or am I off base. I had an exact hole jewel replacement with the exception the hole was a .12mm. I set this one and it caused the watch to knock when in the 

dial down position. Would the cure be to swap the jewels from the settings.

If I understand all corectly, then simply the new setting stays higher than needed and in fact it doesn rest on endstone setting, but stays above it.  Then, if You press the new setting down untill it rests on the endstone setting, the things will get as they should be. If so, You will need to fix the settings sonmehow in this position, for example by making a washer that will stay above the settings and limit their movement up.