If the balance wheel’s weight is not correctly distributed, then you will end up with a heavy spot, or an unpoised balance wheel.
When a watch is in either the dial up or down position, the balance wheel will be horizontal and therefore the effect of any uneven weight will be virtually negated. However if the watch was placed on its side; in the 12, 3, 6 and 9 high positions, then as the balance wheel will be oscillating the heavy spot will have a noticeable effect on the timekeeping on the watch, as it will add and subtract momentum from the oscillating balance wheel
This is called a positional error. As the watch has a fault in a certain position.
Positional error is not always caused by a poising problem. In a modern watch balance wheels are built, assembled and adjusted by machines and so they almost always leave the factory without issue. A more common cause of a positional error would be a fault with the balance spring or with the balance wheel jewels or pivots for example.
However if the balance wheel otherwise looks fine, then it is fairly straightforward to check for a poising problem and correct it if necessary. This is called static poising.
There are some additional ways that balance wheels can be poised, or the effects of an unpoised wheel can be averaged out.
6 comments
DanielB
23 September, 2013 at 1:05 am
Another great blog entry! I was shown to blow air with the dust blower to give the balance a swing. That being said, I like your brush technique and will give it a try. I have a steel jaw poising tool and it works for me. Cheers!
Hi
It is mentioned above “ The jaws can be adjusted independently to one another, and so here we have lowered the right jaw to ensure that it is perfectly parallel to the left one.“ I’m wondering how can you adjust them independently?
I do have a Levin poising tool that have the same problem; one jaw is higher than the other and I don’t know how to adjust them. It will be very nice if you will explain with more detail how to do the adjustments. Many thanks in advance
The sides of the jaws will usually have a screw or bolt in the side that you can loosen and adjust the jaws as needed.
I have previously owned a set of jaws that were steel and could not be adjusted and so if they were not parallel you would need to file the tops of the jaws flat.
Hi, I am wondering where you acquired the brush you have pictured in your article “How to poise a balance wheel”? I an interested in purchasing it or one like it. Thanks in advance ! D
Hi Duane, I think the brush would have been part of the kit you receive as a WOSTEP student, so I don’t know where exactly it came from. It’s just a dusting brush though, nothing special, with one of the hairs bent. Colin
DanielB
23 September, 2013 at 1:05 am
Another great blog entry! I was shown to blow air with the dust blower to give the balance a swing. That being said, I like your brush technique and will give it a try. I have a steel jaw poising tool and it works for me. Cheers!
Colin
24 September, 2013 at 1:47 am
Thanks a lot Daniel! A dust blower would work well too, although i do like the fact the hair can also be brake if needs be.
Doreen
15 January, 2020 at 10:59 am
Hi
It is mentioned above “ The jaws can be adjusted independently to one another, and so here we have lowered the right jaw to ensure that it is perfectly parallel to the left one.“ I’m wondering how can you adjust them independently?
I do have a Levin poising tool that have the same problem; one jaw is higher than the other and I don’t know how to adjust them. It will be very nice if you will explain with more detail how to do the adjustments. Many thanks in advance
Colin
17 January, 2020 at 10:50 am
Hi Doreen,
The sides of the jaws will usually have a screw or bolt in the side that you can loosen and adjust the jaws as needed.
I have previously owned a set of jaws that were steel and could not be adjusted and so if they were not parallel you would need to file the tops of the jaws flat.
I hope that helps.
Colin
Duane Funk
20 January, 2023 at 1:50 am
Hi, I am wondering where you acquired the brush you have pictured in your article “How to poise a balance wheel”? I an interested in purchasing it or one like it. Thanks in advance ! D
Colin
23 January, 2023 at 9:54 am
Hi Duane, I think the brush would have been part of the kit you receive as a WOSTEP student, so I don’t know where exactly it came from. It’s just a dusting brush though, nothing special, with one of the hairs bent. Colin