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More info about truing calipers please!


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I just learned that the above tool is called a truing caliper, and from what I gather or conclude by searching the Internet it can be used to determine if a balance wheel and/or a train wheel is in good condition. That is, that the wheel does not wobble vertically or horizontally. I also believe I read somewhere that a truing caliper can be used to rectify a faulty wheel, but I may have misunderstood?

Anyway, I always wanted a method to at least be able to determine that all train wheels and the balance wheel are in good condition, that they don’t wobble, that the pivots are perfectly straight, and so on. Would a truing caliper like the one in the picture help me achieve this, or would there be a better option? I guess as the balance is freely visible it’s pretty easy to determine if it wobbles in any direction, but what about the train wheels?

If someone can shed some more light on this tool and its use I’m sure more than I would appreciate it!
 

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The only use of this I have seen are to bring back out of round balance wheel or level the rim on one.

I don't see any use of this with an escape wheel. 

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17 minutes ago, Nucejoe said:

I don't see any use of this with an escape wheel. 

Thanks joe! So, that brings me back to my major question about what would be a the best or a good way to determine that all train wheels and the balance wheel are in good condition, that they don’t wobble, that the pivots are perfectly straight and so on.

Based on your reply I would assume that a truing caliper is the best option for a balance wheel, but what about the train wheels, for example, an escape wheel? How can we best determine that it is perfectly straight when it comes to how the wheel rotates between its jewel bearings, that the arbor and the pivots aren't bent, etc.? I guess eyesight goes a long way, but in the realm of micro mechanics a few hundreds of a millimetre do count and I would assume aren't always visible?

Edited by VWatchie
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Hi, 

Three are following your thread and the only response( mine) didn't really address your questions, that means bunch of us are waiting to learn from answers given by knowlegable folks here  @oldhippy & @nickelsilver  and more.

I had a watch that ran accurate FU & FD but inaccurate in pendent up or down , took me couple of months to find the cause was out of round balance wheel. 

I am self though you know and this was several years prior to start of this forum.

Regards    Joe

 

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Hi  These poising calipers come in various design like the one attached below and all do the same job. That is to say determining whether a balance rim is running flat and also not out of round. Never having had to use on  train wheels as yet does not mean to say that the same principal can not be used to determine the same. If and when you have to change a train wheel arbour you have to set it up as was (flat and parallel to the arbour) and in the round so as not to cause depthing problems and intermittent stoppages of the watch/Clock.  I have used a home made device for checking clock wheels  after pivoting and checking after mainspring breakages spinning the wheels in the lathe and monitoring its flatness and round.

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The Bergeons above are specifically for checking balances for flatness, and in the case of split balances for trueness in the round (a solid balance that isn't round or is eccentric is a bigger problem than what these can handle). The pivots are held by the conical portion, and quite a bit of force can be exerted on the rim to bring it true. The adjustable "finger" is for a visual reference while truing. The truing itself is done simply by finger or with non marking stout tweezers.

 

The one below is a typical caliper for checking and truing train wheels. It holds by the end of the pivot, in V shaped cups. The little tool with the dovetail filed in is the traditional visual reference, it is simply slid around until a point is near the wheel rim, the wheel turned by hand, and checked for flatness. That little dovetail tool is usually one of the first projects a student makes in school, I don't think they sell them (I think my daughter made this one a couple of years ago as a project, hahah). Adjustment is carried out with stout tweezers, with one tip pressing in the center by the pinion, the other side of the tweezer is lifting on the rim at an arm. If a bend is discovered between two arms then the correction is at both arms. Bending between arms is a good way to kill the wheel. Obviously a bit of feel is developed to not strain the pivots.

 

To check pivots for straightness the best is to run them in a lantern in either a Jacot tool or in the turns. If you have a good lathe with good collets that can be used too, I regularly check and straighten balance pivots in my lathe.

 

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Thank you very much @nickelsilver! For an enthusiast like me this kind of info is really priceless. Despite being explained in a clear and detailed language with illustrations I still need to struggle to fully understand and create a clear image of the procedure.

One of the things that I struggle to get my head around is the thing about using a "lantern" in a Jacot tool. I got myself a Jacot tool some time ago but having no prior experience of micro mechanics or education in this field I can't figure out what a lantern is. My native language is Swedish but trying to translate "lantern" just doesn't make any sense to me.

Oh well, I realize that I must look like a hungry chick that demands you to feed me, but to don't worry, I realize your time is limited and I'll will of course eventually figure it out if you haven't got the time (or interest, which I'd fully respect) to elaborate.

Anyway, again, thanks a ton for the input!

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A little while back, I made this set of trueing calipers.  It was originally meant to tide me over until I could buy a pretty, vintage, German pair I had my eye on.  It's just a billet of brass which I cut to shape, and where I drilled a single hole through both arms for the pivots, then holes for the set screws which I tapped for threads, then a threaded hole for the reference arm.  The pivots are just thin  steel bar stock with highly polished divots in the ends.  

I keep not getting around to snatching up a nice vintage set.  Mine works well, despite lacking any real aesthetics, so I just keep using it when I need to.  But I swear, one day I WILL pick up a nice German pair.  One day.

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