Bulova 10BZAC beat regulation

[Levine98]

Hi,

FIrst, Happy New Year to all--

I just put a Bulova 10BZAC on my bench and it has an interesting thing-a-ma-jig on the stud screw that I'm wondering if it is used for adjusting the beat error?

I've included a picture from the internet and circled what I'm talking about--the screw that holds the hairspring stud to the balance cock has some sort of cap on it that I'm assuming can turn the stud?

Anyhow if anyone has any experience with this movement would appreciate hearing about it before I attempt to play with it.

Levine98

[Neverenoughwatches]

38 minutes ago, Levine98 said:

Hi,

FIrst, Happy New Year to all--

I just put a Bulova 10BZAC on my bench and it has an interesting thing-a-ma-jig on the stud screw that I'm wondering if it is used for adjusting the beat error?

I've included a picture from the internet and circled what I'm talking about--the screw that holds the hairspring stud to the balance cock has some sort of cap on it that I'm assuming can turn the stud?

Anyhow if anyone has any experience with this movement would appreciate hearing about it before I attempt to play with it.

Levine98

That would help centering of the hairspring if it did. Can you post a close up of it.

[Nucejoe]

40 minutes ago, Levine98 said:

circled what I'm talking about--the screw that holds the hairspring stud to the balance cock has some sort of cap on it that I'm assuming can turn the stud?

What purpose would turning the stud serve?   Did you mean to say "turn the stud arm" ? or stud carirer?  or Beat adjustor arm? 

Rgds

[Levine98]

Here are a couple of close ups--one from the top and the other from the bottom.

[Neverenoughwatches]

2 minutes ago, Levine98 said:

Here are a couple of close ups--one from the top and the other from the bottom.

Is it just not part of the stud carrier. Does it actually turn ?

[Levine98]

9 minutes ago, Nucejoe said:

What purpose would turning the stud serve?   Did you mean to say "turn the stud arm" ? or stud carirer?  or Beat adjustor arm? 

Rgds

I don't know, why I'm asking. However on closer examination under my microscope, I noticed that the stud arm may be adjustable. I'll find out when I clean it and reassemble tomorrow.

Edited January 2, 2023 by Levine98

[Neverenoughwatches]

5 minutes ago, Neverenoughwatches said:

Is it just not part of the stud carrier. Does it actually turn ?

Seems a bit of a new fangled design for a 60 year old watch.

9 minutes ago, Levine98 said:

I don't know, why I'm asking. However on closer examination under my microscope, I noticed that the stud arm may be adjustable. I'll find out when I clean it and reassemble tomorrow.

I cant see how it would change the beat, if it does turn it must have some other purpose. Looked at a few other examples and all are like this. They seemed a high grade movement for the time with 6 adjustments and temperature controlled isochronism. So is this another adjustment feature ?

[Levine98]

I've worked on a bunch of Bulova 10BPAC and 10BOAC. Those two movements share 99% parts and have fixed stud on the balance, making adjustment a real pain.

This is my first 10BZAC and although the base movement looks to be the same as the two above, the stud configuration is different (and I'm hoping adjustable)--maybe it was considered an improvement since according to pink pages the 10BZAC seems to be the a successor to the 10BOAC and 10BPAC movements. 

[JohnR725]

You'll notice your stud holder looks like it's made out of a different material Then the rest the balance bridge. It probably can be pushed and used to put the watch in beat usually when there a different Material that's what happens. It just happens to be a strange design.

[Levine98]

Just an update--it is an adjustable stud arm. However I still don't know what the donut shaped thing is for that is part of the stud holder, but not going to worry about it  

[Neverenoughwatches]

1 hour ago, Levine98 said:

Just an update--it is an adjustable stud arm. However I still don't know what the donut shaped thing is for that is part of the stud holder, but not going to worry about it  

Like John said just a strange feature of the movement.  I was initially thinking that if it turned to center the hairspring it might be some kind of predecessor of an Etachron stud adjuster.

[Levine98]

21 hours ago, Levine98 said:

Just an update--it is an adjustable stud arm. However I still don't know what the donut shaped thing is for that is part of the stud holder, but not going to worry about it  

After assembly and regulation. BTW this was a non-runner bought on eBay for $20. Amplitude dial u/d is closer to 260 with 60 year old orignal mainspring. 

[Nucejoe]

Good show and Congrat Levine. 

If I remember right, hasn't been long since the bug bit you. 

Rgds 

 

[Levine98]

Correct, Jan/23 is my one year anniversary--started with Mark's online classes last January then invested in tools and put together a dedicated workshop in my house over 2022.

I had to give up two other lifelong hobbies a couple of years into my retirement, so endded up with lots more time than planned. Wife encouraged me to take the plunge when she noticed me following several watch repair youtubers for a couple of years.

[Neverenoughwatches]

24 minutes ago, Levine98 said:

Wife encouraged me to take the plunge when she noticed me following several watch repair youtubers for a couple of years.

good wife, look after her. Some  complain rather than encourage .

[EddieZ]

My first time working on the 10BZAC. What lift angle should I be using on my timegrapher ? Mine is a M3, all original parts from what I see.

thanks,

Ed