Superior Knowledge Required

[ftwizard]

I've just rebuilt a movement using a donor movement. It's the same Cal. P 320 as the original, but I need a removed second hand, so had to replace the wheel with the one from the original, with the extended pivot.

The problem is, the new movement has cap jewels for the train wheels, and the donated wheel shaft is too long. It jams if I tighten the cap plate up.

At the moment, I've left the cap jewel off, and it runs fine, but has a lot of end shake. I feel I need to shorten the pivot a little.

The question? Is that the correct way to go about it? If it is, how do I measure it, and how do I shorten it. If it's not the right thing to do, what is?

The picture is of the actual watch, from the auction.

 

 

[jdm]

A diamond file should be fine, followed by buffing stick. I would consider investing a micrometer to see how much are you knocking off.

 

EDIT: mine is not superior knowledge. Just honest advice based on experience and common sense,

Edited August 18, 2016 by jdm

[ftwizard]

So, I measure the wheel that fits, end of pivot to end of pivot, then shorten the other one to the same length? I have half a dozen micrometers, so no problem there.

How would I hold it? Tweezers? I'm thinking it must be incredibly easy to break it off.

Not looking for superior knowledge overall, just superior to mine.

Edited August 18, 2016 by ftwizard

[clockboy]

Is it possible to change the jewel. If so this would be the best & easiest solution.

[jdm]

31 minutes ago, ftwizard said:

So, I measure the wheel that fits, end of pivot to end of pivot, then shorten the other one to the same length? I have half a dozen micrometers, so no problem there.

Send me one then

Quote

How would I hold it? Tweezers? I'm thinking it must be incredibly easy to break it off.

What about the wheel over an holed small block, hold it down flat with an ice cream stick and caress the pivot with the file.

 

Edited August 18, 2016 by jdm

[ftwizard]

26 minutes ago, jdm said:

"Send me one then" 

Yeah I know. I went through a phase of collecting old Starrett and Moore & Wright instruments, so I have a few.

"What about the wheel over an holed small block, hold it down flat with an ice cream stick and caress the pivot with the file"

I think this would be the best idea. I'm sure it would snap off without support.

 

 

Edited August 18, 2016 by ftwizard

[ftwizard]

38 minutes ago, clockboy said:

Is it possible to change the jewel. If so this would be the best & easiest solution.

What do you mean? That doesn't sound that easy to me.

Do you mean move the jewel? Is that possible?

What if I shimmed the cap jewel plate?

Edited August 18, 2016 by ftwizard

[vinn3]

shimming is a sort of "jury rigging"  is it not ?

[transporter]

Ebay search for another movement mate, not being funny but going at it with a file etc there is a massive chance of snapping the pivot, then if you manage to file it down to the correct length you will need to dress the end you have filed otherwise it will run like bag of nails against that jewel.

What's being said so far is possible to do, as for holding it with tweezers id steady it with tweezers and maybe stick it in some pith. The pivots are very hard but extremely brittle so go very carefully if you go ahead without another movement to hand.

[ftwizard]

OK. Is it possible to adjust the cap jewel in the plate. i.e. push it in a little. I don't have a staking tool.

[ftwizard]

21 minutes ago, vinn3 said:

shimming is a sort of "jury rigging"  is it not ?

I got a bit desperate  

[jdm]

25 minutes ago, ftwizard said:

I got a bit desperate  

How much difference are we talking about ?

[ftwizard]

I haven't measured yet, but if I loosen the cap screw by one turn, it's enough to free the wheels.

Also, I think the bottom jewel could move down a little without causing any problems. It's just a matter of the best way to do it with limited tools.

Edited August 18, 2016 by ftwizard

[szbalogh]

 Adjusting pivot lenght (endshake) is done by trial and error, file down a bit and then try it.... until it has no endshake but spinning freely. 

Pivots are shortened (and polished thereafter) on a Jackot tool or on a dedicated pivot polishing tool:

 

 

[clockboy]

I hope you are dong this move it with a jeweling tool. You must move the jewel precisely so if the wheel teeth no longer mesh to can put the jewel back to where it was originally. What I have read it seems that the pivot is only a fraction too long. If so you can hone the pivot down BUT use the correct tools either a lathe or a jacot tool & hone it down gradually. However if the set up is the same as the second pic below my original suggestion is the best because if it does not work no un-reversable damage has been done. But again use a jeweling tool & measure the pivot with the tool below. This is a relatively simple job providing you use the correct tools. If you have not got the correct tools I suggest you purchase another bridge.
Also see below a pic of the two types of pivot/jewel set up so you can see what you are trying to achieve.

 

Pivot measuring tool.

[vinn3]

yes, honeing;  it is better than fileing.  hone stones are available in 3  degrees of  grit.   vinn

[david]

Ftwizard,

If the original staff wasn't binding and running then its pivot is probably the correct length. I would first measure the original staff and compare it to the replacement staff. If the pivot on the  replacement staff it too long then it will need to be shortened. This is done with a Jacot Tool (using the lantern) and a burnisher. If you go Youtube and pull up a Steffen Pahlow video called "MAKING A GLASUTTE BALANCE STAFF",  you can see how the pivot end is filed down on a Jacot Tool. There are also many watch repair books that cover this subject.

david