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Techniques for straightening watch pivots

karlmansson

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This started as a comment in a different thread but I thought it might deserve its own. I've seen questions on pivot straightening pop up ever so often. I hope to gather a smorgasbord of different techniques here, if people care to share!

I've always been a little confused with the various pivot straightening tools present in the tool market. Most of us have a very accurate way to both hold cylindrical pieces and check for runout: the lathe. For clock parts, depending on the size, I either chuck the pivot in a collet in my Lorch 6mm or in my 102 W20 bench lathe (collets go down to 1mm). Then it's just a matter of seeing how far in the pivot will go into a well sized collet, clamp it where it won't go in further and then rotate the spindle by hand and see where the highest point is in relation to a tailstock center. Then you just keep going, heating if necessary in the middle of the process. I don't think I've snapped a pivot in this way, but then again I've only attempted pivots that have been less than 15 degrees off or so.

My 6mm collets go down to 0,4mm so they are still too large for watch work. I've heard about using a jacot to straighten but here I have more or less ONLY managed to snap pivots off. My experience so far is that any attempt to straighten by rotating is bound to be a disaster. I need to find a way to push the pivot true in a jacot. Maybe rest with the highest point of the pivot down and press down on the arbor? But then the elasticity of the steel will make the pivot spring back when I release as it will only hit the bed as the furthest point.

Any suggestions? How do you deal with bent watch sized pivots? Always re-pivot?

Regards
Karl
 

gmorse

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Hi Karl,
My 6mm collets go down to 0,4mm so they are still too large for watch work.
I was fortunate when I bought my 6mm some years ago that it came with a reasonably complete set of collets, including all the sizes from 1 to 8 and only a few gaps after that up to 50. I do use it as first choice if a pivot is not too badly bent, but of course the definition of 'badly bent' does vary with the nature of the material. It's mostly down to feel when deciding how far is too far!

Regards,

Graham
 
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Skutt50

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I hate bent pivots specially if it is the pivot for a seconds hand.... I would rather straighten a hairspring......lol

I also use my lathe but fit the arbor in the chuck and then a pair of heated pliars. Slowly rotating the arbor and slovly closing the pliars around the bent pivot sometimes does the trick, but far from always......

I have had some thoughts about straightening balance pivots. Does straightening not make the pivot weaker and a candidate for future bends compared to a non corrected pivot?
 

DeweyC

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This started as a comment in a different thread but I thought it might deserve its own. I've seen questions on pivot straightening pop up ever so often. I hope to gather a smorgasbord of different techniques here, if people care to share!

I've always been a little confused with the various pivot straightening tools present in the tool market. Most of us have a very accurate way to both hold cylindrical pieces and check for runout: the lathe. For clock parts, depending on the size, I either chuck the pivot in a collet in my Lorch 6mm or in my 102 W20 bench lathe (collets go down to 1mm). Then it's just a matter of seeing how far in the pivot will go into a well sized collet, clamp it where it won't go in further and then rotate the spindle by hand and see where the highest point is in relation to a tailstock center. Then you just keep going, heating if necessary in the middle of the process. I don't think I've snapped a pivot in this way, but then again I've only attempted pivots that have been less than 15 degrees off or so.

My 6mm collets go down to 0,4mm so they are still too large for watch work. I've heard about using a jacot to straighten but here I have more or less ONLY managed to snap pivots off. My experience so far is that any attempt to straighten by rotating is bound to be a disaster. I need to find a way to push the pivot true in a jacot. Maybe rest with the highest point of the pivot down and press down on the arbor? But then the elasticity of the steel will make the pivot spring back when I release as it will only hit the bed as the furthest point.

Any suggestions? How do you deal with bent watch sized pivots? Always re-pivot?

Regards
Karl

Hi Karl.

I can tell you the best use for the Seitz pivot tool is to break the pivot. The second best use is to use it for measuring pivots (has 1/2 sizes).

I agree with both Graham and Skutt. A slightly bent pivot can be straightened. I do it with a Jacot. When it breaks, I repivot.

Skutt is right about the microfractures that occur with a hard pivot. Hopefully it breaks before you return the work.

With the carbide micro drills available today, it is not such a chore to repivot. And if precision timing is your goal, then a "straightened" bent escapement pivot is probably going to interfere with your objective. Further down (up?) the train it is not as much of an issue.
 
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Jerry Kieffer

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This started as a comment in a different thread but I thought it might deserve its own. I've seen questions on pivot straightening pop up ever so often. I hope to gather a smorgasbord of different techniques here, if people care to share!

I've always been a little confused with the various pivot straightening tools present in the tool market. Most of us have a very accurate way to both hold cylindrical pieces and check for runout: the lathe. For clock parts, depending on the size, I either chuck the pivot in a collet in my Lorch 6mm or in my 102 W20 bench lathe (collets go down to 1mm). Then it's just a matter of seeing how far in the pivot will go into a well sized collet, clamp it where it won't go in further and then rotate the spindle by hand and see where the highest point is in relation to a tailstock center. Then you just keep going, heating if necessary in the middle of the process. I don't think I've snapped a pivot in this way, but then again I've only attempted pivots that have been less than 15 degrees off or so.

My 6mm collets go down to 0,4mm so they are still too large for watch work. I've heard about using a jacot to straighten but here I have more or less ONLY managed to snap pivots off. My experience so far is that any attempt to straighten by rotating is bound to be a disaster. I need to find a way to push the pivot true in a jacot. Maybe rest with the highest point of the pivot down and press down on the arbor? But then the elasticity of the steel will make the pivot spring back when I release as it will only hit the bed as the furthest point.

Any suggestions? How do you deal with bent watch sized pivots? Always re-pivot?

Regards
Karl
Personally I have not had good luck straightening pivots with commercial tools designed for the job nor suggested methods from publications.

These methods tend to suggest bending a pivot in a single direction applying a lot of abrupt stress in a small area. However if the bend takes place slowly while the the pivot is rotating and rests for at least 180 degrees of rotation, the stress is distributed over a much larger area at a much slower rate.
I demonstrate this procedure in the NAWCC workshop WS-117 Beginners Lathe class, but it is hard to explain in words and I am not setup for Videos.

However I may be in luck, well sort of.

Over the years, NAWCC members have expressed some concerns that the school is in the East and they are on the west coast, thus options were discussed. While some courses only require a class room that is easy to find (Sometimes) a Lathe class is another issue in that all machines and tooling would need to be shipped.
It Should be noted that in 2019 The NAWCC worked out an arrangement with Sherline where they would supply all machines, tooling and a class room
Free of charge for a NAWCC Lathe class. They are on the west coast near Los Angeles.

As I was on my lunch break, the Sherline sales manager requested a short on the spot demonstration for their records. Since I did the procedure mentioned above, there is the attached video.


While the video shows a Clock arbor, the procedure is identical for watches. The setup for watches can be seen in the attached photo.
In addition, since this was a on the spot demo, ALL bent pivots should be held in collets, not a chuck as shown in the video. Also for whatever reason the lathe appears to rotating faster than the maximum 250 RPM I would suggest in the video.

The procedure can also be used for and is equally effective on bent arbors.

Jerry Kieffer

DSCN1572.JPG
 
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karlmansson

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Hi Karl.

I can tell you the best use for the Seitz pivot tool is to break the pivot. The second best use is to use it for measuring pivots (has 1/2 sizes).

I agree with both Graham and Skutt. A slightly bent pivot can be straightened. I do it with a Jacot. When it breaks, I repivot.

Skutt is right about the microfractures that occur with a hard pivot. Hopefully it breaks before you return the work.

With the carbide micro drills available today, it is not such a chore to repivot. And if precision timing is your goal, then a "straightened" bent escapement pivot is probably going to interfere with your objective. Further down (up?) the train it is not as much of an issue.
Thanks Dewey! How do you use the jacot to straighten? In my attempts with rotating the pivot I've only succeeded in either breaking it off or scoring/flattening the pivot beyond repair. Spinning it under a burnisher loads the pivot unevenly.
 

gmorse

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Hi Dewey,
The second best use is to use it for measuring pivots (has 1/2 sizes).
That's all I use mine for, but as for buying one new (at around £550 the last time I looked) . . .

I suppose doing it in a Jacot tool, one would use a polished, flat (and lubricated) piece of steel to gently press the pivot back into shape as it turns.

Regards,

Graham
 

DeweyC

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Thanks Dewey! How do you use the jacot to straighten? In my attempts with rotating the pivot I've only succeeded in either breaking it off or scoring/flattening the pivot beyond repair. Spinning it under a burnisher loads the pivot unevenly.
Hi Dewey,


That's all I use mine for, but as for buying one new (at around £550 the last time I looked) . . .

I suppose doing it in a Jacot tool, one would use a polished, flat (and lubricated) piece of steel to gently press the pivot back into shape as it turns.

Regards,

Graham
Karl,

You start with a large notch and work your way down. Use a bronze or steel piece on top, with oil. This is recommended only for lower classes of work. First class work deserves a new pivot and besides, it will likely break the pivot of first class work. Think even pivots of good quality carriage clocks. But at least you no longer have a decision to make.

Years ago Jerry Faier (AWI Clock instructor) demonstrated a technique to straighten clock pivots using a lathe and a bar in the slide rest as a pusher to move the pivot as it rotates. But this only worked for soft pivots (American Clocks) and even then the success rate was far from 100%.

For me, it is easier to face off the pivot and drill. No time taken to dither on the decision and the pivot is not damaged. If done well, it is undetectable.

Graham,

I am astounded by the prices of Seitz/Favorite stuff. And I am talking about used prices! I encourage people to make their own gauges out of a piece of brass and several friction jewels of known sizes. No need to spend near $200 USD on used plate with many sizes that can easily measured with a $100 digital micrometer.

I poached an idea offered on this list to use broken balance staffs as oil pushers and pivot gauges.

I would like to see more offerings of such elegant solutions that are effective and simple to implement.

As the Swiss say "Why invent a tool when the back of a tweezers will do?" (unless you are Bergeon).
 
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Chris Radek

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I felt clever recently when instead of making a punch, I used an old staff with one pivot, stuck in a flat stake, to punch this broken index pin out.

I agree with Dewey: when you find a clever and simple solution to something, it's nice to share. I like reading these very much.
indexpins-before.jpg
 

karlmansson

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Karl,

You start with a large notch and work your way down. Use a bronze or steel piece on top, with oil. This is recommended only for lower classes of work. First class work deserves a new pivot and besides, it will likely break the pivot of first class work. Think even pivots of good quality carriage clocks. But at least you no longer have a decision to make.

Years ago Jerry Faier (AWI Clock instructor) demonstrated a technique to straighten clock pivots using a lathe and a bar in the slide rest as a pusher to move the pivot as it rotates. But this only worked for soft pivots (American Clocks) and even then the success rate was far from 100%.

For me, it is easier to face off the pivot and drill. No time taken to dither on the decision and the pivot is not damaged. If done well, it is undetectable.

Graham,

I am astounded by the prices of Seitz/Favorite stuff. And I am talking about used prices! I encourage people to make their own gauges out of a piece of brass and several friction jewels of known sizes. No need to spend near $200 USD on used plate with many sizes that can easily measured with a $100 digital micrometer.

I poached an idea offered on this list to use broken balance staffs as oil pushers and pivot gauges.

I would like to see more offerings of such elegant solutions that are effective and simple to implement.

As the Swiss say "Why invent a tool when the back of a tweezers will do?" (unless you are Bergeon).
So you use it like you would for burnishing? Only using a brass "burnisher"? Are the rpms about the same as for burnishing? Same pressure applied? Is it necessary to move the brass piece at all (I'm thinking as to prevent the pivot from digging into the brass)? Do you use oil?

Regards
 

Jerry Kieffer

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I have had some thoughts about straightening balance pivots. Does straightening not make the pivot weaker and a candidate for future bends compared to a non corrected pivot?
Skutt
This is a good point.

Not all pivots should or can be straightened but if your procedure only takes a few seconds you have nothing to loss.

In lesser quality movements, pivots are normally of lower quality materials and are generally to soft or brittle hard. In either case, I machine a new staff/ arbor or repivot per your concerns.

However in higher quality movements the "toughness" of the pivot is controlled by the quality and type and metals used along with tight hardening/tempering procedures. Under these conditions there is more flexibility in safely bending a pivot slightly without damage.
Information on metal working limitations can be found in a Machinist hand book or information sheets from a metal supply house.

However, straightening a pivot is only practical if there is no contact that would damage a pivots original surface finish and if the pivot runs true as original.
In use over the years, the procedure in post #5 has covered both of these concerns. The success rate has increased with the quality of the movement.

Jerry Kieffer
 

DeweyC

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So you use it like you would for burnishing? Only using a brass "burnisher"? Are the rpms about the same as for burnishing? Same pressure applied? Is it necessary to move the brass piece at all (I'm thinking as to prevent the pivot from digging into the brass)? Do you use oil?

Regards
Karl,

Yes to all except bronze (bell metal) and not brass. But as I said, only useful on lesser quality stuff.

Hi quality pivots usually break.
 

karlmansson

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Karl,

Yes to all except bronze (bell metal) and not brass. But as I said, only useful on lesser quality stuff.

Hi quality pivots usually break.
Thanks for clarifying! As I mentioned previously that’s my only outcome on the jacot so far. Do you have any method that usually does not break the pivot? Good quality ones as well?
 

Skutt50

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In use over the years, the procedure in post #5 has covered both of these concerns. The success rate has increased with the quality of the movement.
Thanks for your comments.
I have not yet used this method #5 but will give it a try next time I need to straighten a pivot. Is this equally useful for the extended pivot for seconds hands?
 

DeweyC

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Karl,

No, I do not have a reliable technique other than breaking them off. I do not agree with what has been written over the years about softening or using pivot tweezers and such on other than that of lower class work. On lower classes of work, you can get most of the damage out, polish down and fit new bushings. On good quality work you want to preserve the jeweling so it is important the pivot fit correctly.

As I said, today with good carbide twist drills down to 50/100 mm from China, there is little need to do anything but spot the center and drill. In the old days it was not so easy which is another reason why older writings are not necessarily the best advice for today.

Smaller holes can be drilled with carbide ckt board drills with care. I think I showed how I break them off the shank and chuck them up close in the tailstock to reduce overhang.

These techniques can be used in virtually any set up. It is even possible to use the ckt board drills by hand if the lathe T/S does not align with the headstock. Takes practice, slow speed, and a good female center, but it can be done.
 
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Jerry Kieffer

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Thanks for your comments.
I have not yet used this method #5 but will give it a try next time I need to straighten a pivot. Is this equally useful for the extended pivot for seconds hands?
Skutt
Yes, however in order to run true the bend must terminate at the entry point of the collet holding it. If unsuccessful, additional attempts can be made. For watch size parts, it is easy to bump the part further than is required, just take it very easy the the first attempt until you get the feel.

The key to success is the quality and style of the bearing.
For example, if you apply a stationary flat surface to a rotating pivot the result will more than likely be a broken pivot. The issue is that you are applying stress in two directions, One against the bend and the other at about 90 degrees one direction or the other as the pivot attempts to climb against the stationary surface.
The ball bearing eliminates the climbing effect thus about half of the stress, but must rotate against a very small watch size surface to do so. For this I use a 1.5mm x 5mm type 69 open race ball bearing dry without lubrication. A sealed bearing offers to much resistance and cannot be cleaned as required to maintain friction free operation.

Jerry Kieffer
 
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Jerry Treiman

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Levin & Levin (Practical Benchwork for Horologists) show a simple tool and method that I have used successfully to straighten several pivots, and have not broken one yet.
Pivot_strght.jpg
 
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John T.

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Levin & Levin (Practical Benchwork for Horologists) show a simple tool and method that I have used successfully to straighten several pivots, and have not broken one yet.
View attachment 666391
Levin & Levin (Practical Benchwork for Horologists) show a simple tool and method that I have used successfully to straighten several pivots, and have not broken one yet.
View attachment 666391
I just had these finally identified in the tools forum. Anyone ever tried using them on any level? B4D7C13A-6D17-4943-A087-AB15F67FCDB4.jpeg
 

John T.

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I just had these finally identified in the tools forum. Anyone ever tried using them on any level? View attachment 666614
Howdy,
Didn’t mean to be a thread killer. Had those tools for quite awhile never being able to pinpoint what they are for. See screen shot pic from Dave Coatsworth nailing it. Karlmansson explained in that thread how they might be used, heating and mending as needed. I was just curious as to whether anyone had actually used them or seen them used. I twirled one around a bent balance pivot that I actually bent trying to use it and it actually did straighten it back out a bit to the naked eye. I’m sure it would wobble in situ.

Jerry T.’s post of a sure fire solution is interesting but way beyond my scope, being a hobbyist,etc. When they say you have to make the tool that counts me out usually.

Anyhow interesting thread.

John T. DEB48C89-76BD-4423-84DA-BC8276F90DD5.png
 

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