Waltham staff & jewel part numbers...

[flynwill]

I am working on my first attempts at replacing a balance staff.

The subject watches are a pair of Waltham 7-Jewel 12s Model 1894, with friction fit staffs. Which is a good thing as I don't yet have a lathe or the skills to use one. I do have a good staking set, and have already driven out one of the old staffs without incident, so I feel confident I can drive in the replacements without problems.

So with a little searching it appears that the proper staff is Waltham Part #8143, and the Upper/lower pierced jewels (which are broken as well) are part #8251 & #8252 respectively.

However, it appears that these came in sizes, in my searches I find pivot/hole sizes of 10, 11 & 12 (are those mm/100? in/1000?) Is the proper match of pivot to hole the same number? Or the numbers the actual size and some difference is needed? (ie pivot 10 needs hole 11)?

The bulk of the surplus parts I find at places like Dashto do not actually mention the pivot/hole size. Was there a standard that the bulk of the parts are made to (ie 11?) and only the over/undersized parts tend to me marked as such? Will a bulk lot of a dozen staffs typically be all the same or all different? I see the jewel settings sold in packs of 3, what are the chances that was a factory spares set with one each of the 3 sizes?

Any guidance would be appreciated. Thanks!

[richiec]

I checked my 2 waltham parts books and they mention nothing about pivot sizes in them but the rule of thumb is that you put the pivot into the jewel and it should only go tilt about 5 degrees off center if it is the proper size. they actually made two balance staffs depending if the balance wheel has a round hub in the center of the arms. I think the hub type balance wheel is not common. The balance wheel with the hub takes an 8143 staff which is a taper shoulder type while the regular balance wheel takes an 8142. The 8142 is kind of short and stout while the 8143 is very thin with a small shelf on the shaft where it butts against the balance wheel arms.

[flynwill]

Thanks for looking, that's interesting to know.

Yes I believe #8142 is the rivet style staff. I have one of those as well, but that staff is in ok shape -- it just has a hairspring that is going to need some serious tweaking.

I know about the 5 degree test from reading Fried. My current plan is to get a dozen staffs (which dashto has for a reasonable price) as well as a number of jewels, and see what I get and how well or poorly they fit.

[Don Dahlberg]

You are correct that the 8143 came in three pivot sizes 0.09, 0.10 and 0.11 mm. There was a U versions for unadjusted and a OV Hub version.

The hole jewels 8251 came in four hole sizes 0.10, 0.11, 0.12 and 0.13 mm and should be 0.01 mm larger than the pivot. The setting should be 2.03 mm in diameter, with a shoulder thickness of 0.40 and a total thickness of 0.65mm. It also had catalog numbers 13270 and 19347. Another version had a 0.35 shoulder thickness.

The problem is that you can seldom find what you need. You take whatever you can find. Often modern staffs have the largest pivots, so you can polish them down to size if you need to. You can make a pivot smaller, but you cannot make it larger.

A hundred years ago the supply house would match the hole jewels and the staff.
Today we often buy staffs from many locations hoping to get one the right size.

Also check out Uncle Larry at http://www.execulink.com/~lfoord/parts.html

If you want someone to talk to try Jules Borel at www.jborel.com They have the upper jewel for a P11. They also have the one with a 0.35mm shoulder for P10, 11 and 12. (you have to register to look at the parts catalog.) They have the staff with P10.

Don

Don

[flynwill]

Thanks for the help Don. It makes it even clearer why watchmakers tend to horde caches of parts. Also clear that there must be an awful lot of NOS watch material out there that will likely never be used because it is not properly cataloged.

Do you know why the variation in pivot sizes? Was it a gradual change over the production (I think this particular movement was in production for 20+ years so it wouldn't be surprising). Or did they use smaller pivots on the higher grade movements?

As for the different shoulder size of the upper jewel settings, here are the measurements of three that I have:

Upper #1, 2.04mm dia 0.63 thick, 0.33 shoulder
Upper #2, 2.04mm dia 0.62 thick, 0.39 shoulder
Upper #3, 2.04mm dia 0.65 thick, 0.38 shoulder

#1 came from the movement with the rivet style staff, so I'm going to speculate (on an appalling small amount of data) that the 0.35 shoulder corresponds to rivet style staff, and that the rivet style staff is 0.05mm shorter.

The other question is "Why make the lower setting different at all?" The one sample I measured (came from movement #3) measured the same 2.04mm diameter, but only 0.52 thick and a 0.23 shoulder. Now if I had been engineering this thing I would have either made the staff a hair shorter or modified the bottom plate so that the same setting worked in both places.

You're correct in that it might be worth giving Borel a call. You may have noticed however that the staffs are listed in BLUE. I don't know for sure what that means, but in my experience with them it seems to mean that they only think they might have the part somewhere...

Of course I starting on this purely as a learning exercise, I'm just learning a whole of things I didn't expect.

[Don Dahlberg]

I do not know why several pivot sizes were used and how they were changed. The jewel setting with the 0.35 shoulder apparently only came in 0.10 hole size. It was used in 12, 8, 6 and 0 size movements. The jewel setting with the 0.40 shoulder was used in 12, 6 and 0 size movements.

I have done a bit more reading on the model 1894.
Staff 8142 was the rivet version. Length is 4.75, balance seat 1.00, hairspring seat 0.70, roller seat 0.55 and hub length 0.44mm.

As I said before there were three versions of the 8143 friction staff. One was for the "unadjusted balance", one for the "adjusted balance" and one for the "position adjusted balance". The literature that I have suggests using the adjusted as a replacement for the positional. I assume these were all the same dimensions, and the difference was in quality. The listed dimensions were the same.

Don