Use of Jacots Tool

[jdrichard]

Can I use this tool to cut down the size of a pivot in a wheel to fit an existing jewel hole.

If so, how?

[vinn3]

nice

[oldhippy]

A jacot tool is only used to burnish pivots. For the work you want to carry out you need a watchmakers lathe.

 

 

[jdrichard]

A jacot tool is only used to burnish pivots. For the work you want to carry out you need a watchmakers lathe.

 

 

Poop. Thanks for the advice. Can I use a Drumel tool with a pin vice and files? Kind of armature however, I have a gear for a 7750 that just does not fit the jewel holes. This is a Chinese replica of a valjoux movement and I purchased a Swiss gear that needs the pinion filed down. Thoughts?

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[david]

JDRICHARD,

The odds of getting any concentricity using that method would be very slim.. There are now several videos on Youtube that demonstrate how to get good results when turning a watch part. One is a Steffen Pahlow called TURNING A GLASUTTE BALANCE STAFF. There is also a good one showing a guy from the SBHI making a balance staff from scratch using a watchmaker lathe and a graver. Maybe the forum members could talk Mark into putting out a video showing how to turn a staff and pivots.

david

[david]

JDRICHARD,

The odds of getting any concentricity using that method would be very slim.. There are now several videos on Youtube that demonstrate how to get good results when turning a watch part. One is a Steffen Pahlow called TURNING A GLASUTTE BALANCE STAFF. There is also a good one showing a guy from the SLBBHI making a balance staff from scratch using a watchmaker lathe and a graver. The title is TURNING A BALANCE STAFF FOR A WATCH OR CLOCK by SLBBHI HOROLOGY.

 

Maybe the forum members could talk Mark into putting out a video showing how to turn a staff and pivots.

david

[szbalogh]

8 hours ago, jdrichard said:

Poop. Thanks for the advice. Can I use a Drumel tool with a pin vice and files? Kind of armature however, I have a gear for a 7750 that just does not fit the jewel holes. This is a Chinese replica of a valjoux movement and I purchased a Swiss gear that needs the pinion filed down. Thoughts?

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I will make a video about my heretic pivot shaping method, stay tuned! 

[jdrichard]

I will make a video about my heretic pivot shaping method, stay tuned! [emoji3]

Big thanks. I will not give up on this.

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[david]

Jdrichard,

There is a sound mechanical reason that concentricity errors should be kept as small as possible. This is due to a property called moment of inertia.  I don't have the ability to use standard math symbols with my keypad so I will try to use what I have. The formula to describe this is:

I = int (m) R^2, dm.  

m=mass

I=moment of inerita

dm= small particles of mass

R=the radius from the center of gyration

The critical element in this is R^2 (R squared) which means that when the rotating element is not concentric, the error increases by the square of the radius. This is why it is so critical for the watch pivots to be as absolutely centered as possible.

david  

[szbalogh]

20 hours ago, jdrichard said:

Big thanks. I will not give up on this.

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As promised

 

[jdrichard]

Jdrichard,

There is a sound mechanical reason that concentricity errors should be kept as small as possible. This is due to a property called moment of inertia.  I don't have the ability to use standard math symbols with my keypad so I will try to use what I have. The formula to describe this is:

I = int (m) R^2, dm.  

m=mass

I=moment of inerita

dm= small particles of mass

R=the radius from the center of gyration

The critical element in this is R^2 (R squared) which means that when the rotating element is not concentric, the error increases by the square of the radius. This is why it is so critical for the watch pivots to be as absolutely centered as possible.

david  

As an Engineer, I do understand the math. The real question is how to turn a large diameter pivot into a smaller diameter pivot.

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[david]

JDRICHARD,

That question is a most important one in watch part making (not to be confused with watch repairing). A few years ago when I started looking into watch repair as a hobby, I watched every repair video I could get my hands on. Every video that dealt with a watchmaker lathe would begin with a statement that they were NOT going to show how to make a watch pivot. This would be followed by statements that a skilled person could make a pivot that is .1mm or .004" in diameter using only a graver and a T-Rest on a watchmaker lathe. Some claims were made on a previous forum that they could make a staff in less than 10 minutes using only a graver and a T-Rest completely by eye without measuring anything.  I have yet to see anybody do this but I have heard a lot of claims that it could be done. I know that I can not do that.

I have seen two Youtube videos showing pivots turned in this manner but they were obviously well over the .1mm in diameter. The two videos that showed success turning a precision .1mm pivot were made by Steffen Pahlow (TURNING A GLASUTTE BALANCE STAFF) and the old videos of the American Watch Factories (Elgin, Hamilton etc.). Neither of these videos showed the staffs and pivots being made using the graver and T-Rest. In both videos the staffs and pivots were made using special runners and fixtures.

Colin from THE GREAT BRITISH WATCH COMPANY who completed both the BHI and WOOSTEP programs  said that it took him six months of intensive practice to make a correct and concentric pivot. He also stated that it takes him about 8 hours to make one this way. 

 Something that looks like a pivot can be made by turning the end down to about .010" and grinding it in on the Jacot Drum down to .004" with a slip, but in my opinion the way to get something close to factory standards is the way Steffen Pahlow does it. The equipment he is using is not cheap but he figured out the process.

david

Edited September 3, 2016 by david

[szbalogh]

My method is relatively simple and need not much experience. Can be used with a new staff turned with rough pivots and then finished like in the video. It is safe, since nothing bad happens if your hand slips. The pivot will be absolutely concentric since it is turned between centers. With those different polishing paste grades one does not need many files just a flat steel piece. The "stregth" of the file depends on the paste used. Oe can relatively fast go down from 0.3mm (roughly turned pivot in the lathe for example) to the desired 0.1mm pivot. The pivots i made are going into holed jewels with 0.11mm and 0.13mm holes. Ususally i try the plate (hole jewel) on the pivot while it is in the tool and if the tip fits, then i change to a finer paste, grind it slower and do inspections more often. After the shaping of the pivot one can polish the pivot ends and sides as well without mounting in another tool. The drawback is that burnishing cant be done in this tool, since one cant push on the pice hard sideways. I will make close-up pictures of the finished pivots i grinded.

[jdrichard]

My method is relatively simple and need not much experience. Can be used with a new staff turned with rough pivots and then finished like in the video. It is safe, since nothing bad happens if your hand slips. The pivot will be absolutely concentric since it is turned between centers. With those different polishing paste grades one does not need many files just a flat steel piece. The "stregth" of the file depends on the paste used. Oe can relatively fast go down from 0.3mm (roughly turned pivot in the lathe for example) to the desired 0.1mm pivot. The pivots i made are going into holed jewels with 0.11mm and 0.13mm holes. Ususally i try the plate (hole jewel) on the pivot while it is in the tool and if the tip fits, then i change to a finer paste, grind it slower and do inspections more often. After the shaping of the pivot one can polish the pivot ends and sides as well without mounting in another tool. The drawback is that burnishing cant be done in this tool, since one cant push on the pice hard sideways. I will make close-up pictures of the finished pivots i grinded.

Thanks for taking the time to explain this. Is there the remote possibility that I could clamp the gear in a Dremel tool and turn the pivots down using a file and paste. I know this is a reach, but I do not have a watchmakers lathe.


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[szbalogh]

Well, You need at least a wax chuck and mount the gear in wax/shellack and make it centered while the glue is soft.

It wont be concentric if mounted directly in the Dremel.

I would do it like this. Take a 3.2mm diameter possibly brass rod and find its center in the Dremel. Turn a cone in the end. This will be concentric. Now add wax or shellack in the cone and while hot put the gear arbor in it. Then turn the Dremel slowly and with a toothpick align the other end of the arbor centered. I am using an AC speed regulator for my Dremel, or using the low speed stage. Try it first with a piece of steel not with the gear you want to reduce the pivot

Important, dont take out the wax chuck before the job is done. You wont be able to mount it concentric again.

 

[jdrichard]

Well, You need at least a wax chuck and mount the gear in wax/shellack and make it centered while the glue is soft.

It wont be concentric if mounted directly in the Dremel.

I would do it like this. Take a 3.2mm diameter possibly brass rod and find its center in the Dremel. Turn a cone in the end. This will be concentric. Now add wax or shellack in the cone and while hot put the gear arbor in it. Then turn the Dremel slowly and with a toothpick align the other end of the arbor centered. I am using an AC speed regulator for my Dremel, or using the low speed stage. Try it first with a piece of steel not with the gear you want to reduce the pivot [emoji6]

Important, dont take out the wax chuck before the job is done. You wont be able to mount it concentric again.

 

You are one inventive man. Let me think about this method....


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[szbalogh]

Just now, jdrichard said:

You are one inventive man. Let me think about this method....


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Hehe, not my invention

[jdrichard]

Hehe, not my invention [emoji4]

Did take the time to draw or find the drawing.


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