Jump to content

Use of Jacots Tool

jdrichard

By jdrichard
in Watch Repairs Help & Advice

 Share

Recommended Posts

jdrichard Distinguished Member

jdrichard

Posted
  • Author
Posted
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?

Sent from my iPhone using Tapatalk

Link to comment
Share on other sites
david WRT Addict

david

Posted
Posted

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

Link to comment
Share on other sites
david WRT Addict

david

Posted
Posted

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

Link to comment
Share on other sites
szbalogh Super WRT Addict

szbalogh

Posted
Posted
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?

Sent from my iPhone using Tapatalk

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

  • Like 1
Link to comment
Share on other sites
david WRT Addict

david

Posted
Posted

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  

  • Like 1
Link to comment
Share on other sites
jdrichard Distinguished Member

jdrichard

Posted
  • Author
Posted
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.

Sent from my GT-N5110 using Tapatalk

Link to comment
Share on other sites
david WRT Addict

david

Posted
Posted (edited)

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 by david
  • Like 1
Link to comment
Share on other sites
szbalogh Super WRT Addict

szbalogh

Posted
Posted

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.

  • Like 1
Link to comment
Share on other sites
jdrichard Distinguished Member

jdrichard

Posted
  • Author
Posted
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.


Sent from my iPhone using Tapatalk
Link to comment
Share on other sites
szbalogh Super WRT Addict

szbalogh

Posted
Posted

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.

 

wax chuck.jpg

  • Like 2
Link to comment
Share on other sites
jdrichard Distinguished Member

jdrichard

Posted
  • Author
Posted
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.

 

wax chuck.jpg


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


Sent from my iPhone using Tapatalk
Link to comment
Share on other sites
 Share
Go to topic listing


  • Recently Browsing

    • No registered users viewing this page.

  • Topics

  • Posts

    • Jon
      Breitling Navi Heritage (ETA 2892A2) seconds subdial skippiness...

      By Jon · Posted

      To be honest, they're not a good movement to have in a chronograph for several reasons. The first is the chronograph mechanism is a 'bolt on' module; If you look at the side of the watch case the crown won't be in line with the pushers, therefore only the branded company would have the ability to swap out the module because they aren't designed to be serviced and definitely not by an independent watchmaker. Secondly, the ETA 2892 A2 is a great movement, but when the chrono module is used with it it becomes pants, in my opinion/experience. So, going back to your watch. The problem isn't with the base movement, which is the 2892A2, as there would never be that amount of backlash/flutter in the gear train of that particular movement, it is with the chrono bolt on module that the problem lies and when the chrono sweep second hand is engaged the flutter of the second hand is remedied by the stability of the chronograph mechanism negating that flutter. Everything in the chronograph mechanism of that movement is powered by a wheel in the centre where the cannon pinion/driving wheel would normally be. I think it is a crappy design deliberately engineered to be disposable due to the time taken to service the module. Give me a 7750 any day!
    • Neverenoughwatches
      Citizen Technical Info

      By Neverenoughwatches · Posted

      Yeah not much going on in the town , Scarborough is a bit better,but the missus and me love York. Good antique shops there, The antiques center on stonegate has a good selection of vintage watches, top price though.
    • oldhippy
      Good evening and hello there.

      By oldhippy · Posted

      Thank you for your introduction and welcome to this friendly forum. We all look forward to your contributions and continued involvement. 
    • Chief
      Citizen Technical Info

      By Chief · Posted

      Brid isn't what it used to be, I only really go to Morrisons in brid. I avoid the town. But Scarborough is nice! I don't mind a wander round the beach between jobs
    • Simeon
      Orient Automatic Crystal and Bezel

      By Simeon · Posted

      I have had a few issues with my Orient Automatic crystal and bezel. The bezel came off with a case knife and I haven't been able to refit it. Doing a bit of research on here, I think that it is an arrangement where the crystal is snapped over a lip on the caseback and then the bezel is installed over the top like a tension ring. I have managed to crack the crystal trying various attempts to press it onto the case. Measuring the crystal with Vernier calipers, I think it is a Sternkreuz XS 314.171 but I can't correspond that to the reference/ case number on the caseback. I also measured the outer diameter of the lip on the case that it may fit over and this is 30.5mm, which is actually 0.7mm bigger than the static inner diameter. Is it likely that the crystal can be expanded enough to snap over that? The inner diameter of the bezel/ tension ring is 32.2mm which works with 31.4+0.7 = 32.1mm Does this sound correct? What method should I use to snap the crystal and then bezel into place? I have a cheap case back press with nylon dies but I managed to break the old one with this method.       
×
×
  • Create New...