Saturday at 8:52 AM
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G'Day Karl!
I suspect that it is somewhat newer technique taught at WOSTEP. Dewey Clark has fairly recently been attending course at WOSTEP school in Neuchatel, CH, and I remember him telling of truing balance and other wheels as well as about preparation of truing callipers for the work, by each student at the time. Perhaps he can shed some light on the subject. BTW, very few watchmakers actually talk about techniques they employ. For example, in UK, there is mailing list with mostly pro watchmakers, and very few were actually talking of the techniques they used routinely, if you do not count Alan Lewis, Dewey Clark, Matt Henning, Mark Pleshinsky (Aussie), Mike Kibby (occasionally) and only couple of other people including myself.
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Thanks for dumping me into the pot Dushan!
OK. I have about 6 different styles of calipers that I use depending upon my physical condition on that day (seriously). But generally, I use the lyre (Levin) style. Always under a microscope at 20 to 40x.
I have corrected many "destroyed" bimetallic balances with compound bends. For most balances the work is done in the calipers. In class we learned to correct very stubborn Glucydor balances. So it can all be done. Just have to decide that you can't make things worse.
For some situations, I use the Horia tool as a clamp (on the ARMS) as Karl's friend seems to have described and as I was taught. But I do not see a good way to provide the needed pressure on the assembly with a standard staking tool. Perhaps an issue with translation Karl? This is also helpful with the Glucydor balances. They take SERIOUS force to correct.
OK. For train wheels the traditional caliper is fine. The cone bearings are fine on the larger train pivots which will withstand the needed forces.
I even have a caliper that will accept barrel pivots.
But, balance assemblies do not like cone bearings. You just put in a new staff. You need to protect those pivots. You need the safety type runners as found in the Levin, Bergeon and other calipers.
Secondly, when making adjustments, the calipers must be TIGHT. You want all the pressure on the pivot cones.
Start by checking the plane of the arms. If out of plane, then one side is bent. If this cannot be seen visually, then put into the watch and decide which has the better clearance for the pallet bridge and center wheel. I mark the low side in red. Just develop a marking system and stick with it.
Also, I set the balance ABOVE the pointer. Again, pick a convention and stick with it.
The out of plane has to be corrected before proceeding further. Use the Horia if needed. Then I adjust the free arms by plain sight.
Replace in the caliper. Pick the worst out of flat free arm. The low spot will be closest to the pointer in my convention. Set the pointer to just clear the low spot at 10x. Mark the low spot. Rotate balance to determine where the bend starts. Repeat until the pointer shows no difference at 10 or 20X.
Unless a compound bend, this can be corrected in the caliper. Now do the other side.
Increase magnification and repeat until you can detect no change at 40x.
Now loosen the caliper for free play. Spin the balance and watch at 20x. You should see not wobble.
Now correct out of round. I adjust the pointer to show the joint of the steel and brass. There is nothing to be done with a solid balance other than verify it is correct or must be replaced.
Again, starting at 10 or 20x. Ensure both arms lengths are equal. I never encountered a balance from a reputable company that had been not been vandalized that arms were unequal. This is all about checking your datum; like first establishing arms are in plane.
Now at low mag, check the runout of one free arm. Correct if needed. This is somewhat paradoxical. The arms by definition are temperature sensitive. You
expect them curve inwards at 90 degrees F. I use bronze tweezers to make the adjustments as much as possible.
One side then the other. Reiterate at high mag.
Now check for flatness once again at high mag.
Adjust caliper for free play and spin. Joy.
I think this is pretty complete, but ....
The point is to develop a system. Just like every other aspect of watchmaking. Establish a datum, marking and SEEING before "correcting". (Dewey)