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Transferring hairsprings between same-calibre balances


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Hi all,

I have an old Bulova that has been on and off my workbench for a few months now - it was one of the first watches I attempted to service. The original staff was bad, so I ordered another movement of the same caliber (8AH, or ETA 1000) in the hope of transferring the balance complete. After receiving the parts movement, I then completely fouled up the hairspring on the "new" balance, due to a tragic combination of large overlapping centre wheel and the softness of old Bulova hairsprings (I now never dangle balance wheels from the cock - a harsh lesson learned).

I've just got a staking set, which makes transferring balance springs pretty painless. The solution to my problem seemed obvious - put the old spring on the new balance. I did it, and it's running well with decent amplitude and minimal beat error. The problem is that the watch is running 2 mins slow with the regulator as far to the "fast" position as it can go.

I was aware of the risk here, as I know hairsprings are vibrated to specific balance wheels. However, I thought it wouldn't be a huge problem given that the watches are the same caliber. How wrong I was! My instinct is that the new wheel is too heavy for the old spring, causing the slower frequency. Is there anything relatively painless I can do to address this problem, or am I out of luck, barring getting yet another donor movement? I really just bought this watch for practice, and cosmetically it's a mess. I don't see the point in dumping more money in. Hoping there is a quick fix, but prepared to live with a slow watch a few times a month.

Thanks in advance,

John

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2 hours ago, JohnC said:

 The problem is that the watch is running 2 mins slow with the regulator as far to the "fast" position as it can go.

Running slow and by two minutes a day.

You need to reduce the working length of the spring, by about 1 to 3 mm, since you have a beat adjustor arm, this can be done with only one try, since there might be no need to reset the impulse pin in-beat.

This being your first try, do not cut the extra( free length) of the hairspring so you can go back in case you made a mistake.

Show a close up of adjustor and regulator arms and the rate so we may give you a closer estimate of the length to be shortened.

Regs 

Joe

 

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3 hours ago, JohnC said:

I was aware of the risk here, as I know hairsprings are vibrated to specific balance wheels. However, I thought it wouldn't be a huge problem given that the watches are the same caliber. How wrong I was! My instinct is that the new wheel is too heavy for the old spring, causing the slower frequency. Is there anything relatively painless I can do to address this problem, or am I out of luck, barring getting yet another donor movement? I really just bought this watch for practice, and cosmetically it's a mess. I don't see the point in dumping more money in. Hoping there is a quick fix, but prepared to live with a slow watch a few times a month.

Outstanding in that you did this. I thought I was going to have to give my classic lecture on why you can't do this but you solved that problem as you did it and it doesn't work congratulations. Then yes I'm really happy you did it because having given the lecture of you can't do this it's nice to have a proof that you really can't. If it's an American pocket watch hairsprings wrh vibrated separate from the balance wheels. This is because the terminal curve's have to be in a very exacting position. Balance wheels were matched to the hairspring they had the timing screws to do it. Although I have wondered on a modern Seiko watch for instance with the etachron system whether there be enough room with the regulating arms to work around this problem as they do of a lot of range.

As usual the multiple ways of solving problems. There is the modification to the hairspring described above and the method that I'm going to describe below.

It looks like the link below your balance wheel has screws on it? If it didn't have screws you could still do this with a carbide drill. You would drill indents on the bottom rim of the balance wheel lightning it this is where a poising toward be really nice to keep the poise. Unfortunately it's going to be trial and error.

As this is a really tiny watch and those are tiny timing screws that makes for an interesting challenge. Basically you're going to have to lighten opposites pair.  Than at the second link I snipped out an image at one time they made a special tool just to do this. It has a handle like a screwdriver a tube on the end. Inside the tube is a  cutter and as it describes the text below will cut a hollow recess into the screw head. That would be perfect to have right about now but unfortunately unless you find someone eBay I don't think they make them anymore. Worst-case you can attempt to file the screw heads.

 

 

So either you need a shorter hairspring or a lighter balance wheel.

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&ETA_1000

https://antiqwatch.com/master-watchmaking/tools-and-materials/467.html

 

balance screw cutters.JPG

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I see now its a fixed stud holder( Dr ranfft), so if your poising skil is decent, increasing the weight( inertia) of the wheel is actually the prefered approach as opposed to shortening hairspring length, for the simple reason that you will loose some amplitude with shortening hairspring length. 

 

 

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Posted (edited)

Thanks guys. @JohnR725 yes this movement is paying dividends in teachable moments for sure. @Nucejoe yes unfortunately a fixed stud.

So the ideal way here is to take weight out of the timing screws. Am I right that this is not a poise issue? So what I want to do is lighten the wheel by the same amount all the way around the circumference, working on opposite pairs of screws? I see screw cutters floating around on eBay, so I guess this is a possibility (although I would have to wait a while - my budget has taken a hit from the staking set).

This definitely seems easier than altering the hairspring, as I have spent a lot of time getting it nicely concentric and as I said, it is very soft and prone to distortion.

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Go carefully, I recently trashed the hairspring on an Omega 455 (movement 16mm dia) whilst trying to add timing washers. I've never seen such small timing screws. My smallest washers were much too big, so I was trying to file them flat when disaster struck.

This is where a balance holder becomes really useful https://www.watchrepairtalk.com/topic/17417-balance-tack/?do=findComment&comment=149926

 

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53 minutes ago, JohnC said:

So the ideal way here is to take weight out of the timing screws. Am I right that this is not a poise issue? So what I want to do is lighten the wheel by the same amount all the way around the circumference, working on opposite pairs of screws? 

You are right( I said it wrong in my post) , yes you lighten the wheel, however, keeping the wheel poised is easier said than done and if you attempt it with hairspring on the wheel, its then dynamic poiseing so we keep increasing the stakes and if you remove the hairspring then one normally risks increasing beat error " that is if we now have the  least to zero beat error". 

I don't think I can add anything to what Mike and John have already said, I personally have a safety razor to take the spring off the wheel with and a nail clipper to cut , so I choose the cheapest route to getting the job done.Unless one plans to become a jobber, cost of acquiring tools can add up insanely. 

Good luck.

 

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@mikepilk
that is a super cool tool. Sorry to hear about the Omega. I feel your pain on those small ladies watches - I recently broke a staff on a 464 and was pretty sad about it.

Thanks all, I have called this one "done" until I have the scratch to buy a tool to do the screws. I had to case it up, as having it in a state of disassembly for so long was driving me insane. Here's a pic of the old fellow - to be continued.

 

IMG_20210103_184618716_HDR.jpg

IMG_20210103_184640269.jpg

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On 1/3/2021 at 6:47 AM, JohnC said:

The problem is that the watch is running 2 mins slow with the regulator as far to the "fast" position as it can go.

Can you repin the hs a tiny length shorter.

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1 hour ago, JohnC said:

Here's a couple of sets, not too expensive. Anything in particular I should be looking for when buying?

https://www.ebay.com/itm/393059419271

https://www.ebay.com.au/itm/162597979187

The first link looks brand-new in the box. The problem with the set is you can't see the cutters there hidden inside the ends. Although if you're lucky they've seen very limited use solar probably in fine condition. There is no way of knowing until he actually get the set and try it out.

 

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2 hours ago, JohnC said:

@JohnR725
@Nucejoe
@mikepilk
Here's a couple of sets, not too expensive. Anything in particular I should be looking for when buying?

https://www.ebay.com/itm/393059419271

https://www.ebay.com.au/itm/162597979187

 

I have some of those balance screw cutters. You need some way of holding the balance securely, without damaging it, as you have to press quite hard to cut. Ideally you would take the hairspring off, but then you have to cut the screws, put the hairspring/balance back together and check the timing. Then strip it all down and repeat as necessary. Each time risking damage to the hairspring.

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@JohnR725
thanks, yes that's what I was thinking of. What the heck, I'll bite the bullet.

@mikepilk
yes I would assume I would have to remove the hairspring. Not sure how I'm gonna hold it... Between a stump and a hollow punch on the staking set? Just spitballing here, did not think that far ahead! 

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@mikepilk glad I found your old post where you asked about exactly this.

I have now had the same realization - I don't want to make a practice of marring screwheads. I'd rather undercut or file the slot. What did you decide on? Did you find the right file for the job? Thanks.

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6 hours ago, JohnC said:

@mikepilk glad I found your old post where you asked about exactly this.

I have now had the same realization - I don't want to make a practice of marring screwheads. I'd rather undercut or file the slot. What did you decide on? Did you find the right file for the job? Thanks.

I've been trying to find a slotting file to cut the screw heads, but haven't found one fine enough. Nor have I found any under cutters. So I ended up using the balance screw cutters. As long as you don't cut too much, it looks OK (usually it's a very small amount to remove).

I just hold it with a finger against a staking block, without taking the hairspring off - which is how I damaged the Omega hairspring 😧.  If you have one of the balance holders I mentioned above - it would be easy.

Depending on the size of the balance, you might be able to use a staking set - press down on one of the balance arms with a flat ended punch ?

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26 minutes ago, JohnC said:

Thanks @mikepilk
ill think it over. Would definitely prefer undercutters but as you say they may be hard to come by.

From the size of the movement, I don't know if you can get undercutters that small?

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Yeah, I think I am going to leave that movement for a bit. However in general I want to start replacing staffs, and following up with truing and poising. I've bought a couple of big pocket watches to practice with, so just want to get the equipment in order.

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21 hours ago, JohnC said:

@jdm
i think this is what Joe suggested above. I have never done this but it's a thought. However Joe thinks lightening the balance is preferred.

Sorry, I didn't realize this balance has screws. Maybe just my opinion, but dealing with a pin seems so much easier than fiddling with extremely small screws to remove material.

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