Selecting the correct balance shaft

[JohnTosto 1]

Hello everyone

this is only my second post (1st in intro).

I have a project pocket watch that I am working on (something for my younger son he like ww2 era ) lucky for me there seems to be a lot of scrappers out there (couple wheels had a bent or broken pivot) however not the greatest luck getting one with a good balance shaft.

I would like to try my hand at balance replacement, I have staking set tool and other necessary tools, below are the pocket watch details.

• elgin 16s, 7j
• grade 291
•  model 7 
• Class 110 
• Man yr 1943

I found the manufactures part number for the balance shaft (861) but then quickly discover (after searching ebay) there are a few version how do I determine which is the correct one, both pivots are gone.

[nickelsilver 693]

That's probably not the best watch to do your first staff on. There are probably at least two different pivot size options, then perhaps differences in the roller table fitting or balance hole diameter. Add to that it likely has been restaffed at least once to several times, and the balance jewels may be cracked or have been changed to different/wong size in the past.

All that said, there are references out there that should indicate the theoretical correct staff, a couple of members here have the info and will certainly chime in. Give it a try, but if you hit a snag don't get discouraged- it could be several things outside of your control.

[JohnR725 648]

Balance staffs for Elgin watches are always a challenge, pivots are not necessarily a prime problem right now?

Elgin balance staff numbers are interesting in that one number can refer to a whole bunch of different staffs not just pivots size variation. So for instance is This a old-style or a new style I'm going to attach snippets out of various PDFs. So first problem I'm having is from the normal source I look at its indicating it's a single roller but yet your picture is showing a double roller? This then requires going to a different book to find out it could be both? So I'm attached additional images it looks like it's not a problem it's listed as a single roller staff but it can have a double roller.

The first step with replacing a balance staff is measuring the old staff. This will avoid any unnecessary complication of problems later on or surprises. So remove the hairspring and the rollers. Then also depends on how you're going to remove the staff? If you're going to cut the staff out before you do so you need to take all of your measurements. Otherwise you can attempt to knock the staff out  and take your measurements after.

There are two purposes of measuring the staff first to verify what which staff that is second to measure the new staff to verify it has all the same dimensions. So differentiate between the two staffs it appears to be the total length and the hub size. You'll have to guess on the total length which is problematic without pivots if you're lucky the hub size will give you a clue. Then as you can see four different pivots sizes. This is where having a watchmaker's lathe is really nice in that if you're lucky you'll get the biggest size you can shrink to the smaller size if necessary. But as a guess because this is a seven jewel watch it probably has larger  pivots.

Then if you think this is complicated celebrate that you don't have the 18 size staff number 857. It comes in four different variations with some of those having up to five different pivots sizes. Most of the watch companies have unique numbers for each of their staffs not Elgin unfortunately.

 

 

[JohnTosto 1]

Hello all,

Thanks for taking the time to respond hoping you don't mind a couple follow-up questions.

Again very new to this, is there somewhere I can get my hands on an Elgin factory parts book or pdf or better yet a source were I could find parts books for all different manufactures?

I might be getting into the weeds but I have a few of the same grade (which had the same wheel and shaft part number) movements and found two that appear to have good balance shafts.

• Overall measurement of original shaft with both pivots broken is 4.80 mm, haven't removed roller yet (tool coming in mail) so really no other measurements
• 1st balance wheel/shaft I have overall measurement is 5.35mm with pivot of .13mm. This spins freely with balance cock seated but not screwed in and the moment I tighten down slightly it no longer free spins.
• 2nd balance wheel/shaft I have overall measurement is 5.27mm (which doesn't make sense unless it because the pivots are worn) and pivots of .12mm. This one spins freely even with the balance cock tighten however I found even if I apply slight pressure on the cock there is no effect. 

Based on the above here is what I concluded and hoping you will tell me if I am off base , correct or somewhere in between.

The overall length I want is 5.32mm,  my guess is why readings are not dead on to the chart  is my fear of damaging pivots while measuring, regardless I believe that wheel with overall measurement of 5.27 to be too short as I understand that slightly pushing down on the cock should stop the wheel or you have too much end shake.

I feel that .13mm pivot is too large and is why when have the 1st balance wheel installed stops moving freely when the cock is slightly tightened.

If I am correct with the 2nd balance wheel overall length is an in between measurement of what the charts say and its because it is worn then not a fair test for pivot size and it is possible if correct length I could see same results as 1st wheel. I have read in other posts that pivot size can be checked by placing one of the jewels on the pivot and it should just slightly pop out but is that a fair test if I suspect the pivot is worn?

[JohnR725 648]

I don't think there is one source of all PDFs related to watch repair in the universe. This is because it would take up a sizable quantity is space I have a moderate collection which is at 20 GB. Of discs I've bought over the years from eBay and a variety of sources downloaded etc. So most people don't have the bandwidth the store 20+ gigabytes of tech sheets.Then this doesn't even really scratch the surface of datasheets sometimes the answer questions on this group I have to physically scan something as it's not PDF anywhere. It would be nice if there was some magical source in the universe that had all known horological datasheets but it just doesn't exist.

So for pocket watches there is the pocket watch database found at the link below. Notice under the title various watch company names? So under each of these are subcategories of the various things that have been accumulated. Like for instance blank number two the Elgin Logs. If you scroll down far enough you get to one of the material guides inches length three.  Then this is by no means all of the Elgin stuff. I purchased a disk off of eBay that has a 1915 illustrated Elgin parts guide which is really nice because the 1927 just has the part numbers.

Did you notice in nickelsilver's Reply above the reference to things might've been changed over time? Working on vintage watches is interesting it's not black and white like modern watches were parts interchange where a predictable happy outcome is almost guaranteed it just doesn't Necessarily happen with vintage even if you think you know what you're doing.

The fourth link something interesting to watch.

So I've given you some stuff to get started.  Then my brain just isn't processing the rest your questions due to being distracted by rumors of a plague affecting the universe.

 

 

https://pocketwatchdatabase.com/

https://pocketwatchdatabase.com/guide/company/elgin/catalogs

https://pocketwatchdatabase.com/guide/company/elgin/catalogs/elgin-watch-co-material-catalog-c.1927

https://youtu.be/ys4ChOWYNy8

 

[JohnTosto 1]

Thanks again for the information, the long and short of it is I think I might have made a few missteps when I was trying to use parts from a couple of scrappers I had that  i used pocketwatchdatabase.com helped identify.

Looks promising as I found a good balance wheel, hairspring and shaft of the same part number and after cleaning seems to swing freely after mounted.

I think I need the NS 861 .13 pivot shaft based out of what I was able to pull from the scrappers of same model and order one from ebay.

I already purchased a K&B 602R that came with the balance staff remover so hopefully this weekend I will have successfully replaced the broken shaft.

Thanks again

 

regards,

john

 

[JohnTosto 1]

Hi All

 

Thanks everyone for their help, I successful replaced the balance shaft, it took me two tries however learn from my first mistake and now on to the next issue.

Regards

 

John