Valjoux 72c Minute Recording Jumper/Pawl

[sstakoff]

Working on a vintage Heuer V72C. Just fully disassembled and all basically OK except the minute recording jumper is fractured

I believe it is part #8270.  Anyone have a line on a reasonably priced source for this part??? I suppose I can make one but thats a bit more work than
I was hoping to do on this piece.

Thx,

Stu

[HSL]

That part is insanely expensive nowadays, one has to be really carefull working with them especially when polishing the functions.
There are two versions of this movement and both are availible on ebay..

Version 1.
https://www.ebay.com/itm/VALJOUX-23-72-72c-88-PART-8270-MINUTE-RECORDING-JUMPER-SPRING-NOS/264722494307?hash=item3da2b0b363:g:DZUAAOSwF7lcMxT1

Version 2.
https://www.ebay.com/itm/VALJOUX-23-72-72c-88-PART-8270-2nd-Version-MINUTE-RECORDING-JUMPER-SPRING-V7/202640976401?hash=item2f2e57ea11:g:gMAAAOSwzAhdcrYW

Edited July 13, 2020 by HSL

[sstakoff]

4 hours ago, HSL said:

That part is insanely expensive nowadays, one has to be really carefull working with them especially when polishing the functions.
There are two versions of this movement and both are availible on ebay..

Version 1.
https://www.ebay.com/itm/VALJOUX-23-72-72c-88-PART-8270-MINUTE-RECORDING-JUMPER-SPRING-NOS/264722494307?hash=item3da2b0b363:g:DZUAAOSwF7lcMxT1

Version 2.
https://www.ebay.com/itm/VALJOUX-23-72-72c-88-PART-8270-2nd-Version-MINUTE-RECORDING-JUMPER-SPRING-V7/202640976401?hash=item2f2e57ea11:g:gMAAAOSwzAhdcrYW

Thank you - these parts are so very delicate so it's not surprising that after many decades and however many services that they break. The one I have is slightly fractured and a bit of a twist at the fracture as well. I wonder if there's a way to repair it? I fear that an attempt to solder it will just cause it to break from the heat.  This is the exact same watch as Mark's video: https://www.youtube.com/watch?v=pFOQm9sAzE8&t=932s. He runs into the exact same issue. Mark chose to make a replacement and was kind enough to record the whole process. I am leaning towards doing the same.

In Mark's replacement, I do not believe that he created the alignment pins to the part. I am curious as to whether or not this is a concern as I would not want the jumper to move over time. I was thinking about ensuring the new part was in very close proximity to the balance cock and/or the chrono bridge to prevent rotation.

 

 

[HSL]

They usually are so brittle so if you don't want to buy one I think making one is the best alternative I think, will take an hour or two but is faster than ordering em.
The thing with that minute jumper I guess is that it sometimes will not work correctly, people then tend to bend them to make them "stronger" and they crack, but if one think about it they worked fine as they came from the factory and probably never will lose their springiness.
The trick to get them into shape again and get a snappy  minute tick is to polish the faces of the function ( the part that goes inbetween the gears), this should be mirror polished. Often one can see it is neglected when servicing this beauty. 

27 minutes ago, sstakoff said:

I am curious as to whether or not this is a concern as I would not want the jumper to move over time

On the valjoux 72 version 1 it is fixed into place by two pins and should not move. On the version 2 it can be moved up and down by an excentric wheel.  Both are fixed in place with one screw when in position.

[sstakoff]

That's great advice - thank you. What do you use to polish the function? 
On a related note - I would assume it is equally important to obtain a mirror finish on the surfaces of the hammers and the hearts for the chrono wheels. Would you use the same technique??

Regards,

Stu

[nickelsilver]

I feel that the steady pins are necessary. Especially on jumpers like this that aren't adjustable, once the position is set (you have to adjust the position of the jumper point by filing) then it is set for life. I think he may have left them out to provide a little bit of adjustability, plus it's tricky getting them in the right locations, and you have to make them on a lathe, and press fit, and so on so it's actually a fair bit of work.

[HSL]

 

16 minutes ago, sstakoff said:

I would assume it is equally important to obtain a mirror finish on the surfaces of the hammers and the hearts for the chrono wheels. Would you use the same technique??

I do it much like polishing the pallet fork jewels but with different abrasives, first one hold the function of the part with like a bergeon 30433 pallet fork holder, then under the microscope I gently take away the scratches one can see with a 3M 2500 grit stick. When the parts looks good I polish them of with dialux blue spred on a flattened peg wood.
One could probably use a stong lupe too instead of the microscope.

Edited July 13, 2020 by HSL

[sstakoff]

Thank you! I prefer to do this type of work under the stereo microscope as well. Appreciate the help!

[nickelsilver]

There's a big difference in making a functional part and making one that's right and looks the part too. I think a good minute jumper, that's indistinguishable from factory would take a skilled watchmaker more than an hour or two. If it is steady pinned and unadjustable, and especially if it's beveled, definitely more.

Here's one I did this year for a Longines 30CH. This poor thing had had a jumper from a stopwatch cobbled in, they used one of the steady pin holes for the new screw, so it had been threaded and thus was off location (and the new pins are two different sizes). For this one I used a toolmaker's microscope to locate the steady pin holes and screw hole in relation to where the beak needed to be (hammer down so minute wheel was positioned correctly). Imported an image of an original in cad, scaled it and traced the outline. Cut out the part with cnc, the spring portion oversized, hardened and tempered, thinned the spring down (much easier when heat treated) made and fitted steady pins, fine tuned the beak, polished beak, beveled the foot. That was about a 3 hour job but I'm a prototyper so it's normal work for me, and I have cnc.

I left the steady pins visible (with polished ends) as the locations had been changed and this part likely won't fit another 30CH- a little heads-up to a future watchmaker I hope.

[HSL]

2 hours ago, nickelsilver said:

Imported an image of an original in cad, scaled it and traced the outline. Cut out the part with cnc

That was a good tip, think I will try it out after my vacation, thanx.
Guess it will be some tweaking to get it completely correct.

 

[sstakoff]

Really great explanation - and looks like a beautiful job.

HSL - is that CAD a properly dimensioned part? If so, any chance you'd post the .dwg file???

Stu

[HSL]

The CAD model still has to be scaled, I just took a picture of a minute valjoux 72 minute jumper and imported it to a rapid CAD tool.
One still have to meassure the part under a microscope with a reticule. I don't have one at home with that feature, and I just began my 5 week vaccation.
If you can meassure the distance between the pins and the hole you could scale it quite easy yourself. Just pop me a pm and you can have the file.

 

Edited July 13, 2020 by HSL

[jdm]

4 minutes ago, HSL said:

One still have to meassure the part under a microscope with a reticule.

If you take a good straight picture, and measure the biggest dimension, can't derive all others in software?