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  1. #1
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    Default How much pressure to use

    I've been a slacker and haven't done the pivots on the 1880 key wind yet. Nearly a year in limbo. So, to refresh memories, I have to reduce the pivots on a new staff from P16's to P15's and fit them to the jewels.

    I have a burnisher and pivoter with proper posts in good condition.

    I just don't know how hard to push in order to move the metal and reduce the pivot diameter. I know it's hard to tell me but anything helps. Is it moderately light and lots of bow driving? Or is there a heavy bearing down and only a few turns with the bow?

    I'm thinking Sunday I will try to do this.

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

    Great question Rob, like you I have two movements in 'limbo' which have new staffs and are running great but could do better with a little pivot burnishing... I have the tools, I have the time, I just don't have the experience which daunts me a little

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    Default Re: How much pressure to use (By: Mark UK)

    I didn't get to this yesterday. Just not enough sleep to be steady or able to concentrate. Which lead to no motivation.

    I have a lot of things to do before this one is ready for this step anyway. I have to restaff the balance wheel so I can drive the new staff off the arm (because I don't have the little clip-drive dog things). I have to pull the lower jewel from another movement to replace a bad lower in the 1880 too.

    Once the staff pivots are reduced, I will have to modify the lower jewel chaton to shorten the between-the-jewels distance. This is because the correct replacement staff is not available and I have to use a "new style" staff which is .001" shorter overall. (though I might get lucky and the burnishing might move enough metal to lengthen the pivots enough. I doubt it, but I can hope.)

    I need to check again to see if the front plate escape wheel bushing absolutely has to be repaired/rebushed. I don't like the looks of it, it looks pretty beat up. There's a raised ring of metal around the pivot hole in the plate. But that could be gilding flash.

    At least I made a written list of the things this one needs. That way, if it takes another year to get back to it, I'll at least know where I left off. So, I actually did accomplish something. I definitely feel the itch to get this one off the bench, so I'm looking to find a few hours here and there this coming week. We'll have to see.

  4. #4
    Registered User gmorse's Avatar
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    Default Re: How much pressure to use (By: Rob P.)

    Hi Rob,

    ... This is because the correct replacement staff is not available and I have to use a "new style" staff which is .001" shorter overall. (though I might get lucky and the burnishing might move enough metal to lengthen the pivots enough. I doubt it, but I can hope.)...
    You're right to doubt it, you won't stretch it by that much.

    The burnisher needs to travel about 15mm in each direction for about 50mm of bow stroke, so the pivot is always turning before any pressure is applied by the burnisher, otherwise you risk forming a flat. The right pressure is difficult to describe but it needs to be firm and held so that it produces a cylindrical surface. Checking the fit after every few strokes will soon show you whether you're having any effect. The amount of metal being moved does depend on the hardness of the staff and the way the burnisher is dressed, as well as the pressure you apply. Be careful when burnishing staff pivots that you don't apply any pressure to the cone, or you risk a breakage. Some Jacot tools have a guard to keep the burnisher away from the cone. Mine didn't have one so this is home-made.

    Regards,

    Graham
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    Default Re: How much pressure to use (By: gmorse)

    Thing that makes me procrastinate is finding a suitable staff to turn down to from my pile of unsorted staffs. It's more work to find one that I can make work by adjusting in the lathe than maybe to turn the thing by scratch from stalk. Depends on how lucky I get. I measure length first by guessing (usually have to add for missing/broken pivot and adjust caliper) and then do a "go or no go" through the caliper on the possible staffs. I eyeball the thickness to pick the best of the candidates and then measure and hope they are equal or bigger.

    You ever notice though that it's the first move thing that causes the most delay. I find that if I just open the case or remove the movement then I am prone to continue. But otherwise I just sit and dream about something else. The internet is a time sucking vampire.

    RJ
    The bitter the challenge, the juicy the reward.
    Conquest->https://www.youtube.com/watch?v=MV0F_XiR48Q

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    Default Re: How much pressure to use (By: RJSoftware)

    Hi RJ,

    ...The internet is a time sucking vampire...
    You're so right . . . .

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

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    Default Re: How much pressure to use (By: gmorse)

    I spent a couple of hours this morning on this one replacing the cracked jewel with a pair from another KW I have that's a parts only movement of the same grade. Someone wrecked the heck of of that one, stripped screw holes and everything - it's toast.

    As for the 1880, I got the balance restaffed too. So, all that's left is to fit the pivots to the jewels. I think maybe Saturday I'll try to get back to it for this task. Then we mock it up and see if the overall length works or not.

    I think the scale I'm going to use to describe the pressure needed is going to be from 0 to 10. With 10 being unreasonable and guaranteed breakage and 0 being just resting the burnisher on the pivot with just it's own weight. 5 should be something like light draw-filing on steel. I'm thinking a 3 should be the right amount of pressure. I'll find out.

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

    3/10 sounds about right

    I like the idea of the guard that Graham suggested as I can't afford too many breakages, staffs aren't that expensive but the cost of postage trebles or quadruples the price.

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    Default Re: How much pressure to use (By: Mark UK)

    One good thing to keep in mind that I learned from a helpful someone here is to remember to always rest the burnisher flat on the edge of the BED. Not the pivot. If you rest it on the whole flat of the bed right away you will only contact the tip of the pivot and it will become conical as the tip dips away from the burnisher when the whole pivot is reduced. You need to keep the burnisher in good contact with the edge of the bed at all times. That way you are taking off an equal amount along the lenght of the pivot the whole time. When you are finished the burnisher should be resting perfectly flat on the bed.

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

    Hi Rob,

    You have the right approach; start light and get the feel for the action, checking all the time, and don't forget to keep everything well lubricated. A light spindle oil like 3-in-1 will do.

    That steel guard piece is illustrated and described in "Watchmaking" by George Daniels.

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

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    Default Re: How much pressure to use (By: karlmansson)

    Karl, do you mean rest the burnisher flat on the back edge of bed or front edge of bed? I imagine the answer depends on if you only burnish on the down or up stroke of the bow..... and whether the staff is rotating clockwise or anti-clockwise.... and whether the bed is on left of jacot or on the right.... or am I making it seem harder than it really is

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

    What he said was to just rest the tip of the pivot (the cylindrical part) on the selected Jacot bed. And to set the burnisher/file with rounded corner towards the cone portion of the pivot but first work the cylindrical portion.

    This is what I find. Holding a long burnisher/pivot file by the end and trying to feel if it is laying flat on the oh so small Jacot flats is difficult. What I did cut a small portion of my pivot file so I could use one finger to hold it.

    When I hold a long file by hand and the file does not fit squarely on the flats I find I wind up present the pivot with an escape route and it will roll out. Also is the dreaded snap from when the pivot rolls out of the bed and then binds in crack between flat and file held at not so perfectly square to the Jacot flat.

    So I cut a portion of my pivot file about 1/2 inch long. Then when I set the tip of the pivot in the bed of my choice I carefully lay the file as described and hold my finger on top which has better ability to keep the small portion of file flat to the Jacot flats.

    This increase in control actually allows me to start off with larger stock in the Jacot bed. So I can start reducing a couple/few sizes larger than the goal bed. I really don't have to do anything but hold the portion of file squarely to the bed as it seems to cut just fine. But I move it a small amount anyway for improvement. Some say to load a file with chalk to prevent clogging. Also an ultra sonic is suppose to help in unloading clogged file. But I think that is for larger work. I have not tried it.

    The whole purpose of using the Jacot tool is the controlled reduction. The pivots laying in the bed can only be reduced to the depth of each bed, but they do not start out that way. So they are problematic as the extra height above the bed affects how well one can hold the file to the flats.

    The ultimate solution is like the Roll-o-fit. Where the Jacot tool is held in a device and a controlled arm with a carbide wheel descends in perfect position on top of the pivot to reduce the cylindrical part by micrometer adjustment. All while turning a hand crank and applying simple finger pressure with little skill required.

    I created my own Roll-o-fit type tool and it's base is a vise that I can power my turns, pivoting tool and Jacot. It does not have the controlled arm with the carbide wheel but after cutting the portion of pivoting file I realize that I don't need it.

    I recently installed a window crank for a handle. Basically it's just one upright board with hole for 1/4" all-thread axle that turns a large wood drive pulley with a groove for a rubber-band that drives the Jacot pulley/dog. The upright board is attached to a wood base which has a mini vise screwed down to hold the Jacot. (I hate that my camera sucks).

    Anyway, it makes life easier. To further improve the Jacot situation I put a coil of pocket watch mainspring and cut a notch on end so that I could reach up with the spring and attach it to the balance staff. What I wanted was a way to keep the balance staff (I always have balance wheel attached to drive it) and balance wheel in place. So the spring notch is set on the staff so to keep it from jumping out of the bed -ever.

    It worked so-so. The ability to adjust the downward tension of the spring needed improvement. I could crank the wheel at full speed and it would stay in the bed. But the extra effort to hang the spring on top and not have it pull to hard was issue. The other side of the spring was super-glued on to the Jacot tool and it broke off and I never felt compelled to have it on again.

    I improved my design as of lately to finally get my pivoting drill to work. I made mine out of aluminum with 1/8th inch brass inserts.

    The 1/8th inch size is all about the Dremel. Yes...!!! Love it. Now I have finally made my pivoting drill to use the carbide bits and it works like a dream.

    Well, it' didn't at first. I was going nuts. I got my pivoting tool all done took my time. Then came the Chinese PCB carbide bits. I ordered a bunch of them cause they are cheap. Start off at .1mm so it's small enough to do the staffs and others stuff. (cant' wait to have to do an anchor pivot).

    Anyway, so I get the bits. I get to work on a staff. All needed to do was remove the hairspring and then grind a small flat of the broken pivot which was on the hairspring side.

    So I get to drilling. I look, got a nice dimple. Drill some more. Still only a small dimple. What the heck...?

    I busted a bunch of the smallest bits I had. Kept freaking trying and trying. What the heck is going on.

    Then I realized... the balance wheel was slipping on the staff. So the wheel was spinning away but the tiny staff wasn't turning.. Rats....!

    So I staked the staff on tighter and then whaaaa lahhhh success...!

    I had 5 sets of those drill bits and ate every small one I had.

    Oh and another thing. I had some bust on me as they tend to roll off of a flat surface. So I screwed a magnet to the upright to grab the bit.

    The small drill bits are soo delicate. Like an uncooked blond angel hair pasta from Save-A-Lot.

    RJ
    Last edited by RJSoftware; 04-19-2017 at 08:22 PM.
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    Conquest->https://www.youtube.com/watch?v=MV0F_XiR48Q

  13. #13
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    Default Re: How much pressure to use (By: RJSoftware)

    No RJ, what I said what was Mark was asking about. I usually use the back edge of the bed. But as you say each their own!

  14. #14
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    Default Re: How much pressure to use (By: RJSoftware)

    Hi RJ,

    I believe Rob and Mark are talking about burnishers not files, and the Jacot is really best used for burnishing pivots which are almost to size to start with. I'm not clear how you can give the file/burnisher enough travel if it's only 1/2" long. One thing about placement of the burnisher is that you can hear a different sound from when it's acting correctly on the pivot and when it's just on the edge of the bed.

    Regards,

    Graham

    "Ut tensio, sic vis" - Robert Hooke

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    Default Re: How much pressure to use (By: gmorse)

    I normally use around 1/2" of travel when burnishing small pivots. Maybe that's what RJ meant?

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