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  1. #16
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    Default Re: How much pressure to use (By: karlmansson)

    I think Rob was intending to reduce a pivot size whereas I would like to burnish a few pivots following successful re-staff using 'unfinished' staffs I got from fleabay - so I am probably confusing things.

    I have a couple of oversize staffs but no lathe, but I do have a couple of spare beds that I am tempted to keep to one side just for filing, and keep the good beds for burnishing.

    RJ, those cheap PCB drill sets are pretty handy. I got my monies worth out of a .2mm bit the other day before it snapped on me, so I ordered a few more sets.

  2. #17
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    Default Re: How much pressure to use (By: Mark UK)

    Ok, no problem. I'll explain.

    I do filing on the Jacot and burnishing.

    And yes I physically cut a chunk of my pivot file off the end that also included the one section with the tiny round edge.

    I got the pivot file/burnisher with a bunch of other tools. So I figure why not.

    But, it works.

    If you can't understand how it can still file, ask yourself how many teeth that chunk of file has. Probably in the range of 50 or so... In case of newbians don't understand, a pivot file has teeth finer than frogs hair. It's much finer than even the small jeweler files. The teeth are soo small you have to use magnification to see them. But then now you know why they are expensive.

    Why did I do it? Well, because I have difficulty with my finger sensations. It took me a long time before I could feel ant bites or even hot water on my left leg. My arms and legs have difficulty with sensation and numbness.

    This is not a pity thing. I am doing well. I am use to it and I don't even think about it hardly.

    But, the issue is there.

    So I resolved it. Now I can place my finger firmly on the small piece of pivot file and then turn the crank which powers the Jacot which files the pivot down.

    Now you guys say... well your' suppose to have pivots mostly done and only need to slightly modify I guess.

    Ok, but seems sometimes I miss the mark. But I get there...

    So say the objective is to produce a common staff with pivots at 9. I crank out a staff on the lathe and wind up with pivots at 11. I just do the rest on the Jacot tool with the pivot file. Why not?

    Lay the 11 size pivot in the 10 bed, put the piece on top and turn the crank. I do a little wiggle so to improve the cutting but not much. Before you know it, it's done. Then I move to the 9 bed and same thing.

    The last step I do burnishing.

    Thing is I might not be in the same quality of results as you guys. But what I do works.

    RJ
    The bitter the challenge, the juicy the conquest.
    Conquest -> https://www.youtube.com/watch?v=NGaVUApDVuY

  3. #18
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    Default Re: How much pressure to use (By: RJSoftware)

    I see what you mean now RJ.
    Does give you good results? What you are describing is basically turning as your file isn't moving but the work is. The pivot files I have are all cross cut. That means that they need to be kept moving or the grain of the file will imprint on the work. A burnisher on the other hand, that is "single cut" perfectly perpendicular to the work, will leave no such imprint. It also needs to be kept moving though to prevent any buildup of metal particulate from scoring the pivot. That and any lateral movement will average out the inconsistencies in the burnisher.

    I see how this is the optimal solution for you, considering your condition. But I think the visual and sensory aid of a longer burnisher is preferable for someone with well functioning sensory systems. It's easier to tell if your tool is slanting if it's longer. And it's also easier to tell if you're rocking the burnisher of its long.

  4. #19
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    Default Re: How much pressure to use

    Well I figured it out. A 3 or maybe a 4 is about right. You don't need a lot of pressure to either reduce or burnish. Mostly it's the speed of the bow that does the work. I also wiped the tool with oil rather than dropping oil onto the pivot. Much less messy and the pivot got oiled during the work.

    Unfortunately, I snapped the pivot during the final burnishing after I fit the thing to the jewels. I knew I probably would, but I'd hoped not to. My luck is like that - do everything perfectly up to the very last second then BAM!, it's ruined and now I get to start over. Oh well, off to find a new staff.

    I did notice I had a pretty good step at the bottom of the cone. Is this normal after reducing pivot size? Or do I not have enough of a rounded edge on the file? Hmmm, maybe I need a new file too...

  5. #20
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    Default Re: How much pressure to use (By: Rob P.)

    The step is sometimes there but the goal is to have no step. You should burnish the cone as well, just take care not to put the pressure concentrated on it. That will snap the pivot. I think pivots reduced by the Pivofix machines often have a rounded step after burnishing. at the very least the step should have a radius.

  6. #21
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    Default Re: How much pressure to use (By: karlmansson)

    I looked at my tooling; the rounded edge which should go next to the cone is pretty sharp. So I'm going to do some shaping on it. I can still use this staff for more practice.

    What was interesting to me was that the pivot snapped halfway rather than at the bottom next to the cone. I still can't see how I managed it, the pivot was fully filed and the tip was not even near the edge of the cradle when the tool slipped into the gap between the cradle and the bed. I shouldn't have been able to damage it at all, but when it slipped I heard that tiny snap and knew it was gone even before I visually checked it.

  7. #22
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    Default Re: How much pressure to use (By: Rob P.)

    Hi Rob,

    I'm not sure what you mean by the cradle, is it the land behind the bed without the recess for the pivot? When you're reducing a pivot to fit in a given jewel, it's better not to file until it fits fully, but until it just about fits, then burnish the rest of the way to a proper fit. In theory, it doesn't matter if there's a step if all the part of the pivot that fits in the jewel is cylindrical, but it does look better aesthetically.

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

  8. #23
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    Default Re: How much pressure to use (By: gmorse)

    Rob, I've had the same thing happen. The cause is trying to burnish too much. You should get it down to where you are a couple of thousands away from final dimension, either on the late or by using a pivot file. The staff breaks like that due to stresses in the material. It's like bending steel wire back and forth. The staff work hardens and the more you keep compressing it the harder it gets. Finally it gets dead hard all the way through or
    the stresses from the pressure you apply gets too much. While
    burnishing takes off a minuscule amount of material the majority of the reduction comes from compression.

  9. #24
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    Default Re: How much pressure to use

    Graham, I've wondered about the "trumpet" shape of balance staffs. My understanding is that it's there as a compromise between a thin pivot and a strong pivot. It grows thicker as the leverage from the jewel increases. In other words, there should be no weak spot where the staff can break if subjected to shock. But wouldn't a staff with a step in it from burnishing have such a weak spot?

  10. #25
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    Default Re: How much pressure to use (By: gmorse)

    Quote Originally Posted by gmorse View Post
    Hi Rob,

    I'm not sure what you mean by the cradle, is it the land behind the bed without the recess for the pivot? When you're reducing a pivot to fit in a given jewel, it's better not to file until it fits fully, but until it just about fits, then burnish the rest of the way to a proper fit. In theory, it doesn't matter if there's a step if all the part of the pivot that fits in the jewel is cylindrical, but it does look better aesthetically.

    Regards,

    Graham
    Terminology, I suck at it.

    What I call the cradle is the part with the semi-circular recess for the pivot. It cradles the pivot while you work on it.

    The bed is the wide flat hexagonal area. There's a gap between the cradle and the bed - maybe 1/16" wide.



    I believe the cone is just a stress relief radius. Sharp corners in metals that are stressed tend to break at the base of the shoulder. A radius reduces that chance.

    While I'm looking for a new staff, I'm going to get some wire and make a set of pivot gauges. I'll get more practice and hopefully won't break the next staff. And I get new tools too!

  11. #26
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    Default Re: How much pressure to use (By: Rob P.)

    Hi Rob,

    ...What I call the cradle is the part with the semi-circular recess for the pivot. It cradles the pivot while you work on it.
    The bed is the wide flat hexagonal area. There's a gap between the cradle and the bed - maybe 1/16" wide...
    I think you have that the wrong way round; the bed is the part with the pivot recess, and the part behind it is just the backing flange to support the burnisher. We all suffer from jargon!

    I should have added that the sweep of the cone from the cylindrical part of the pivot does make for a more robust job, as you rightly point out.

    If you haven't already got it, one of the most useful tools I can think of is a copy of "Watchmaking" by George Daniels.

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

  12. #27
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    Default Re: How much pressure to use

    I know this is true because I have done it a few times. Also this is why I go ahead and file with the pivot resting in a larger bed then when that is done proceed to next smaller till I get to target size.

    It's the control of the reduction provided by the Jacot bed that has it's appeal for using early vs struggling with measure on the lathe which sometimes promotes a snap.

    I have the microscope lens with the grid lines and pin gauges to do comparing. But these are rough estimators. Sometimes using them alone I fail at critical measure such as the hairspring collet portion. That one is more critical to me than even the roller side. This is because I can taper/feel my way for the balance wheel seat and taper/feel the roller. The hairspring/collet is too awkward to test so I wind up sticking the best fitting pin gauge in the collet and go from there. Many times I cut a tad bit too far and then I try to compress the collet to restore the grip. I can compress it with cone punch. But not always.

    Thing is, it's hard not to just try to slap the whole thing out with the lathe and then the Jacot. I have turn by centers and I have shellac chuck both are good solutions but I also just want to get the job done and find that I don't want to bother to set up either.

    I have to force myself to be more systematic. Of the two (turn by centers or shellac). Turn by centers is easy to remove and measure. Shellac you have to unglue.

    I see some people grab the jewel with some Rodico or similar and test fit the pivot. That would work on the lathe but for me, I don't know. I hate to drop stuff.

    If I can master the jewel on the stick trick, then I can skip the tbc and shellac.

    RJ

    Quote Originally Posted by karlmansson View Post
    Rob, I've had the same thing happen. The cause is trying to burnish too much. You should get it down to where you are a couple of thousands away from final dimension, either on the late or by using a pivot file. The staff breaks like that due to stresses in the material. It's like bending steel wire back and forth. The staff work hardens and the more you keep compressing it the harder it gets. Finally it gets dead hard all the way through or
    the stresses from the pressure you apply gets too much. While
    burnishing takes off a minuscule amount of material the majority of the reduction comes from compression.
    Last edited by RJSoftware; 04-24-2017 at 07:29 AM.
    The bitter the challenge, the juicy the conquest.
    Conquest -> https://www.youtube.com/watch?v=NGaVUApDVuY

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