Turning a balance staff--check my numbers

[LittleWatchShop]

This topic is part of my Cyma watch repair, but I thought it would be a good stand-alone thread.

Background:  I am trying to make a staff for a Cyma watch.  I had the original staff but it flew away.  So, I start from scratch.

The Bestfit manual indicates that the staff is a Besfit number 242.  I have compared the Bestfit numbers to those on balancestaffs.com and they comport well enough.

Not all numbers are provided (e.g., the length of a pivot), so I have measured some pivots of similar sized staffs and used that as a guide.

What I am showing in these two figures are the Bestfit data and my working drawing using the principles I recently learned from @nickelsilver

I would appreciate someone looking over my shoulder and comment on these numbers.

 

I may flip this over so that I can turn starting at the collet side rather than the roller side.

Edited April 24, 2022 by LittleWatchShop
fixed figure

[nickelsilver]

Looks pretty good. I would definitely recommend going the other way though, top side first. One question- does your watch have Incabloc? That will change some things. The pivots seem a bit large in diameter for the size of watch but I reckon you know what they should be. The length you've assigned for the pivot+ conical portion is probably right at the limit, could be slightly shorter but fine there. The taper for the roller looks too steep, most staffs will only have perhaps 0.05mm difference over that length at that start dimension. I'd drop the diameter above the hairspring collet diameter a bit, maybe 0.5 or 0.55. But looks good. If I recall correctly you do have a slide rest, no? What steel will you be using?

[LittleWatchShop]

6 minutes ago, nickelsilver said:

watch have Incabloc

No, just a fixed cap jewel.

6 minutes ago, nickelsilver said:

The pivots seem a bit large in diameter

I will check these again.  If I measure the hole in the jewel (which I can do easily with my tool), how much should I back off from that number?

8 minutes ago, nickelsilver said:

could be slightly shorter

I just took a SWAG at that number...will reduce it a bit

 

8 minutes ago, nickelsilver said:

The taper for the roller looks too steep

Another SWAG, but was looking at your taper when I came up with it.  Will adjust.

11 minutes ago, nickelsilver said:

I'd drop the diameter above the hairspring collet diameter a bit, maybe 0.5 or 0.55.

Not sure I understand this.  I was following the published number...assuming we are talking about the same dimension.

12 minutes ago, nickelsilver said:

ou do have a slide rest, no?

I have a three-axis cross slide.  Right now there is no attachment or assembly for a rest.  Maybe I need a picture of what you mean. 

Once I get your comments I will update the images.

[nickelsilver]

Sorry, too hard to quote-quote- For the pivots, at this size watch, about 0.01mm under the hole size is good for the pivot. On the taper for the roller, if you look at my drawing there's 0.01mm taper, haha, yes it's quite a small staff. You have 0.19mm on the drawing, that's a lot. The diameter above the collet- not listed on the Bestfit, it's the diameter above "D". Probably not an issue at the dimension you have though.

 

Slide rest= cross slide, unless talking to a regular machinist (for them a cross slide is the slide that has the crank in front of your belly when standing at the lathe). I highly recommend trying yours out if you haven't already, it is a life changer.

[LittleWatchShop]

3 minutes ago, nickelsilver said:

if you look at my drawing there's 0.01mm taper, haha, yes it's quite a small staff. You have 0.19mm on the drawing

my bad...I took ratios, not linear distance.

 

5 minutes ago, nickelsilver said:

Slide rest= cross slide, unless talking to a regular machinist (for them a cross slide is the slide that has the crank in front of your belly when standing at the lathe). I highly recommend trying yours out if you haven't already, it is a life changer.

OK, I am attaching a picture of what I have.  While I have wanted to use it, the backlash drives me nuts.  Time to rethink I guess.

Attached is an updated drawing though I have not revisited the pivot diameter yet.  I reduced the pivot length, diameter of the region to the right of the collet and fixed the taper on the roller side.

I am using blue pivot steel now, but I can switch over to silver steel...I have some.  Not sure I have mastered hardening, however.  Have not mastered anything yet, frankly.

Using two different hole gauges, I measure the jewel hole on the balance cock be 14.6 and 14.7.  The gauge is marked in integers so I interpolated between 14 and 15 to get these numbers.

[LittleWatchShop]

This is better...measure w/r to the starting point.

[Klassiker]

Is B=205 or 230?

[praezis]

The taper for the roller is still much too steep. 
A taper about 1:50 is used, so the 62 will come to 59 at the end (not 47).

Frank

[LittleWatchShop]

3 hours ago, Klassiker said:

Is B=205 or 230?

Ah...good eye.  Let me do a revision.

Here is my progress so far

48 minutes ago, praezis said:

The taper for the roller is still much too steep. 
A taper about 1:50 is used, so the 62 will come to 59 at the end (not 47).

Frank

OK...will adjust

Per dimensions in the horizontal plane (as drawn) A, and B are critical, I believe.  Thus they must not be violated.

From there, I am somewhat on my own but guided by other components (roller, balance arm (beam) and HS collet).  I have measured those to be 128, 30, and 67 respectively (rounding to integer values).

I am thinking the collet shoulder should be longer than 70.  Or at least the combination of that shoulder and the one in series to the pivot (31) should be longer. 

???

Note that the hairspring for this watch has an overcoil.  Thus it does make sense to me to add more length to the hairspring side.

[LittleWatchShop]

Well...it is about the journey, not the destination.  I show the progress here in this figure, but there is a problem.  The dimension for the balance beam hole specified did not work for my balance.  Probably been wallered out over the years of repairs.  Instead of 120, I get 133.  Discovered that AFTER the cut.

I can save it by going back to the pivot and working inward.

[LittleWatchShop]

OK, here it is.  I dont think I gave enough of a depth on the HS side.  I can put it back in the lathe and improve it.  I did not do a single-pass mill.  Instead, I flipped it to do the roller side.  Never would have happened for me the other way.  I have pretty good Levin collets, so it remained quite true after the flip.

This has been extremely hard and took SO many hours.  I have great respect for you professionals who do this regularly!!

While fitting the roller, I noticed that some previous watchmaker crimped it...I guess to tighten the fit on the balance staff that was perhaps the wrong diameter.  Anyway, while doing the fitting, it began to split at the crimps.  Oh well.  I think it will still work.

 

Edited April 28, 2022 by LittleWatchShop

[Neverenoughwatches]

1 hour ago, LittleWatchShop said:

OK, here it is.  I dont think I gave enough of a depth on the HS side.  I can put it back in the lathe and improve it.  I did not do a single-pass mill.  Instead, I flipped it to do the roller side.  Never would have happened for me the other way.  I have pretty good Levin collets, so it remained quite true after the flip.

This has been extremely hard and took SO many hours.  I have great respect for you professionals who do this regularly!!

While fitting the roller, I noticed that some previous watchmaker crimped it...I guess to tighten the fit on the balance staff that was perhaps the wrong diameter.  Anyway, while doing the fitting, it began to split at the crimps.  Oh well.  I think it will still work.

 

Cool. LWS it looks  good.  You've made a decent  looking bal. Staff. How many on  here can say that. Probably not many . 

[LittleWatchShop]

Well, when testing the staff in the watch, I discovered that one of the pivots was a little too big, so I had to chuck it up and turn it down a tad bit.

Now the balance is fully assembled and running in the watch.  Have not put it on the timer because I want to enjoy this victory before taking any hits for erratic behavior.

As noted earlier, the roller is not in great shape. I tweaked it as best I could.  If there is an issue, I will blame it on the roller and not my staff!!!

[LittleWatchShop]

Update on this work.  When I started turning the staff, I found a balance complete on ebay and ordered it.  I needed a backup.  It arrived today and I noticed that it was not a breguet hairspring as indicated on ranfft and also my observation of the hairspring that was on the watch when I started.  I installed it regardless and it is obvious that the hs sits too high and that the regulator pins are short thus supporting the idea that would have been a breguet.

I looked at the hs that came on the watch and it looks like it was modified (bent) to form a breguet arrangement.  Not a great job, but who am I to judge!!

Kind of at a crossroad now.  Maybe I will fit the old hs on the new balance and staff.  Kinda dont want to take a crack at bending an breguet geometry onto a hairspring.

[grsnovi]

What watch is this for @LittleWatchShop

[LittleWatchShop]

3 minutes ago, grsnovi said:

What watch is this for @LittleWatchShop

Cyma 571

[Neverenoughwatches]

On 5/1/2022 at 11:59 PM, LittleWatchShop said:

Well, when testing the staff in the watch, I discovered that one of the pivots was a little too big, so I had to chuck it up and turn it down a tad bit.

Now the balance is fully assembled and running in the watch.  Have not put it on the timer because I want to enjoy this victory before taking any hits for erratic behavior.

As noted earlier, the roller is not in great shape. I tweaked it as best I could.  If there is an issue, I will blame it on the roller and not my staff!!!

Haha lws. You are funny. That's my attitude.  I've made a part for it, it runs. What more can you ask, I don't give a shit as to how it's running I'm pleased it just does, and if its crap then something else must be wrong. Love it haha

33 minutes ago, LittleWatchShop said:

Kind of at a crossroad now.  Maybe I will fit the old hs on the new balance and staff.  Kinda dont want to take a crack at bending an breguet geometry onto a hairspring.

I saw it done, using paper templates. Made it look quite easy, and maybe had a dozen distorted hairsprings in the waste bin behind him.

[Klassiker]

On 5/5/2022 at 10:56 PM, LittleWatchShop said:

Cyma 571

Well, Ranfft says Breguet. My guess is, back in "those days" (1930s), the hairsprings we're supplied coiled, fitted and vibrated to the balance, but unfinished - overlength, no terminal curve - and a watchmaker was expected to have the skills to finish it off, perfectly matched to the watch in question. Does that seem plausible?

[LittleWatchShop]

5 hours ago, Klassiker said:

Well, Ranfft says Breguet. My guess is, back in "those days" (1930s), the hairsprings we're supplied coiled, fitted and vibrated to the balance, but unfinished - overlength, no terminal curve - and a watchmaker was expected to have the skills to finish it off, perfectly matched to the watch in question. Does that seem plausible?

I just don’t know. What you say is plausible, however.

regardless, I am going to have to learn to bens a Breguet.

[nickelsilver]

I haven't seen a balance complete that was intended to have the overcoil formed by the watchmaker, but it could exist. One thing to check- pretty much all Breguet springs have a collet with the hole for the spring significantly lower than a normal collet (normal would be hole right in the middle of the collet height). If your spring is in the middle, it was to be a flat spring.

[LittleWatchShop]

16 minutes ago, nickelsilver said:

I haven't seen a balance complete that was intended to have the overcoil formed by the watchmaker, but it could exist. One thing to check- pretty much all Breguet springs have a collet with the hole for the spring significantly lower than a normal collet (normal would be hole right in the middle of the collet height). If your spring is in the middle, it was to be a flat spring.

The hole is definitely off center. 

[nickelsilver]

1 hour ago, LittleWatchShop said:

The hole is definitely off center. 

Like, it's lower than normal?

[Klassiker]

6 hours ago, nickelsilver said:

I haven't seen a balance complete that was intended to have the overcoil formed by the watchmaker, but it could exist

Likely to exist only in my imagination in that case.

Here is what a balance complete with a Breguet hairspring looks like for the calibre:

https://primetime305watches.com/store/watch-parts/breguet/balances-breguet/cyma-16-1-2-caliber-510-671-670-breguet-complete-balance-swiss-made-1-piece/

[LittleWatchShop]

29 minutes ago, Klassiker said:

Likely to exist only in my imagination in that case.

Here is what a balance complete with a Breguet hairspring looks like for the calibre:

https://primetime305watches.com/store/watch-parts/breguet/balances-breguet/cyma-16-1-2-caliber-510-671-670-breguet-complete-balance-swiss-made-1-piece/

Here is what I purchased.  I have myself to blame, as clearly there is no overcoil in the pictures

I have my eye on a couple of donors as a backup.  One is in the UK and the seller will not ship to US, but another has already made the trip.  As earlier stated, I will attempt the over coil...but I need a backup plan.

I have been in contact with the seller.  This is my mistake due to my inexperience.  The seller offered to refund the sale, but I did not accept it since I clearly could see what I was buying.  Lesson learned.

The 571 can come with and w/o the over coil as seen in this document image.

New question.  Is the only difference between the planar and over coil implementations the regulator pin length?

Although the package shows a breguet.  Whatever

 

[praezis]

14 hours ago, LittleWatchShop said:

New question.  Is the only difference between the planar and over coil implementations the regulator pin length?

The whole piece is different. Breguet regulator pins have less distance from center than flat hairspring ones (unless you have a very very rare "100" curve).

Frank