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What Exactly Happens To A Mechanical Watch During The "break In" Period?


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I have a few questions of you horologists out there. Many times I have heard the advice to wait until a watch has gone through the "break in" period before making adjustments to get it to run accurately. Exactly, what is happening during this time period? Is it gear wear, lubrication break in, an overall geshtalt of relationships between moving parts etc...? Is there a difference between letting the watch run for a month unworn vs wearing it every day? If the actual wearing and associated movements is what effects whatever gets "customized" internally, can changing those wearing habits affect accuracy after the break in period? What exactly is the purpose of a COSC rating if the actual accuracy will change with use? Is it not a reflection of out of the box accuracy but rather an indication of "potential" accuracy once the watch is settled into user specific wear? How can they possibly predict this? Does one need to have a watch re-adjusted every time usage changes?????

Thanks

Chris

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I think you're mistaking reps with gens here ...

Well my genuine COSC rated SMP chrono ran like a top out of the box almost daily dead on but after 7 monts of 2-3 day/week use and 24/7 run time, it's now +7 sec/day. Is this an anomaly among genuine COSC watches and should I ask my jeweler for a free in warranty adjustment?

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When you're not wearing the watch, try experimenting with setting the case in different positions (e.g. dial up, dial down, crown left, right, etc). Some positions will cause your watch to run faster, slower, or dead on due to gravity, side load and so on. If you have your COSC certificate, it should list which positions your specific watch generates +/- as I believe they time the watch in the different positions over the course of their evaluation.

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it's now +7 sec/day. Is this an anomaly among genuine COSC watches and should I ask my jeweler for a free in warranty adjustment?

If your watch isn't COSC, you can get a warranty repair, I reckon.

Seconds per day:

Average daily rate: -4 +6

Mean variation in rates: 2

Greatest variation in rates: 5

Difference between rates in H & V positions: -6 +8

Largest variation in rates: 10

Thermal variation: +-0.6

Rate resumption: +-5

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When you're not wearing the watch, try experimenting with setting the case in different positions (e.g. dial up, dial down, crown left, right, etc). Some positions will cause your watch to run faster, slower, or dead on due to gravity, side load and so on. If you have your COSC certificate, it should list which positions your specific watch generates +/- as I believe they time the watch in the different positions over the course of their evaluation.

It sits in the box on it's...well whatever that thing is, dial up pitched at about a 30 degree forward angle. I'll try it in some different positions. I recall John H from the Poor Man's watch group posting how one obtains the COSC certificate for their chronometer. I think it involves actual letter writing and is not doable via the web.

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I have a few questions of you horologists out there. Many times I have heard the advice to wait until a watch has gone through the "break in" period before making adjustments to get it to run accurately. Exactly, what is happening during this time period? Is it gear wear, lubrication break in, an overall geshtalt of relationships between moving parts etc...? Is there a difference between letting the watch run for a month unworn vs wearing it every day? If the actual wearing and associated movements is what effects whatever gets "customized" internally, can changing those wearing habits affect accuracy after the break in period? What exactly is the purpose of a COSC rating if the actual accuracy will change with use? Is it not a reflection of out of the box accuracy but rather an indication of "potential" accuracy once the watch is settled into user specific wear? How can they possibly predict this? Does one need to have a watch re-adjusted every time usage changes?????

Thanks

Chris

As I understand it, the break in period allows the lubrication, which may have settled, to work through the moving parts of the watch. The main thing is in the balance and escapement. As the balance wheel has less friction due to the dispersement of lubrication, it is able to rotate more smoothly. If it doesn't travel its entire arc, the watch goes faster than it should because each rotation allows the escape wheel to advance the time by one beat. That is why a new watch slows down some over the break-in period.

Take it for what it's worth. I'm very much a novice, but I'm learning. If I'm totally off base I'm sure someone will correct me, but from what I've read, that is the basic idea of the break-in period.

Edited by shimside11
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As I understand it, the break in period allows the lubrication, which may have settled, to work through the moving parts of the watch. The main thing is in the balance and escapement. As the balance wheel has less friction due to the dispersement of lubrication, it is able to rotate more smoothly. If it doesn't travel its entire arc, the watch goes faster than it should because each rotation allows the escape wheel to advance the time by one beat. That is why a new watch slows down some over the break-in period.

Take it for what it's worth. I'm very much a novice, but I'm learning. If I'm totally off base I'm sure someone will correct me, but from what I've read, that is the basic idea of the break-in period.

I thought lubrication was only at the bearing points.

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