Servicing my Hamilton 992B Railway Special - Model 2 - 1947 - Pt 2

JimInOz · May 6, 2017

Thanks for the help gents. The guidance and information given is appreciated more than you could imagine.

I decided to check everything again under the microscope. And what did I notice about the balance on the poising table?

While the pivots are not centred correctly in this video, the "high spot" is always where the pivot is in the "sag" position so the balance may be poised but the error is caused by the pivot.

It's times like this I feel like going back to motor bikes, but I don't want to give up.

So, do I use my staking set to correct the bent pivot (I don't have a pivot straightener attachment)?

Or bite the bullet and order a new staff?

Canuck · May 6, 2017

From the sound of it, you have rather high expectations of this watch. I suspect the pivot may have damage other than the bend. Should you succeed in straightening the pivot and repairing any other damage to it, you'll likely end up with a watch that you will never be able to make perform as well as it seems you would like. I'd replace it if it was my job.

JimInOz · May 7, 2017

Canuck
From the sound of it, you have rather high expectations of this watch. I suspect the pivot may have damage other than the bend. Should you succeed in straightening the pivot and repairing any other damage to it, you'll likely end up with a watch that you will never be able to make perform as well as it seems you would like. I'd replace it if it was my job.

I think that'll be the best solution, I may try to straighten it in the meantime though.

Following your tip, I spent the afternoon trying to get the collect over centre. It was rather exhausting and I had to take a few breaks. Every time I did an adjustment and re-fitted the spring it was a bit different. I finally ended up with this. I'm afraid it will have to do, the concentration and hand skills are almost as arduous doing hard labour!

JimInOz · May 8, 2017

Project now on hold until receipt of balance staffs from USA.

Postie postie don't be slow, be like Elvis, GO MAN GO!

JimInOz · May 24, 2017

Getting items from the USA makes for long wait times, but these have arrived and are ready for the next step, putting the balance assembly back together.

JimInOz · May 26, 2017

I dragged my trusty (rusty) old staking set out for the next step, putting the balance assembly back together.

Here you can see the bare balance wheel on an anvil with the bore sized to clear the upper part of the staff. That's confusing because the upper part of the staff is actually pointing downwards here.

The balance wheel of the Hamilton 992B is an interference fit style where the staff is pressed into the blue steel collet which is permanently fixed to the axis of the wheel. You can see here that the staff has only been set in position with tweezers and is sitting proud of the collet.

Above the staff is the hollow pointed rod or "stake".

This is first checked for correct size. Too big and it will slip over the staff and not do anything, too small and it could jam the staff in the stake.
Next, the hole in the stake is checked for any gunk or left over evidence of previous watchmaker's failures. Remains of a broken pivot or other material could wreck the delicate pivot on the staff so a bit of fine brass wire is used to clean and check the stake hole (I also take them to the garage and use an air gun to blow any dust/gunk out before use).

The stake in the pic above is being held in place by a spring loaded screw, so as I start to set the staff I hold the stake with the fingers of my left hand, loosen the holding screw, and then tap the top of the stake with my hammer (actually an old bit of 4x40x90mm brass plate).

By listening to the sound the hammer makes and feeling the stake moving between my fingertips I can tell when the staff has been seated, and then one more little tap for luck and it's done.

The next step is to fit the rollers, but I didn't take pics of that so you'll just have to imagine.

PS: I really understand now, how much time our other mentors (@Archer, @ChrisN et al) must spend in developing posts like this one (well, I flatter myself a bit saying that).

It takes a lot longer than doing the actual task!

Deafboy · May 26, 2017

JimInOz
The stake in the pic above is being held in place by a spring loaded screw, so as I start to set the staff I hold the stake with the fingers of my left hand, loosen the holding screw, and then tap the top of the stake with my hammer (actually an old bit of 4x40x90mm brass plate).

By listening to the sound the hammer makes and feeling the stake moving between my fingertips I can tell when the staff has been seated, and then one more little tap for luck and it's done.

Without being judgmental, would there have been the option of press fitting the collet to the staff (as opposed to hammering)?

JimInOz · May 26, 2017

Deafboy
Without being judgmental, would there have been the option of press fitting the collet to the staff (as opposed to hammering)?

Not seeing it as being judgemental at all.

Maybe something like a jewelling tool setup could press fit but my jury rigged jewelling tool would probably not give the "feel" needed.

While I said "hammer" I use an old brass plate (not a hammer) so as not to deform the heads of the stakes, and it's not so much a "hammer" but gentle taps while feeling the movement with the fingers holding the stake. The tapping also lets me rotate the wheel every tap so as to even out the force being applied downwards.
Whether this an old watchmakers trick, or even necessary, I feel my engineering background telling me it can't be detrimental.
The sound of the hammer changes as the staff seats and that, with the feel between the fingers, tells me when to stop.

Hope this answers your question, and I would welcome comment from other "watchmakers" and Watchmakers.

ChrisN · May 26, 2017

Neat job Jim. These press fit staffs that don't need rivetting have some advantages as, in theory, you won't disturb the truing of the wheel or the poise so, it's a neat system in some respects. I've not replaced one of these but have read about them and have the stumps in my staking set. I'd use a staking set as well but, you could probably press them in with a Seitz or Horia as an option, if you have a suitable stump.

There are special stumps in some staking sets for these, some examples:

It looks like you selected one of those as it was clear to you that you want to support the blued bush/hub and not the wheel spokes (your spokes look clear of the stump). I use a similar method to you when tapping with the stake but I rotate the stake instead of the job. It just seems natural, as you say.

Now, I assume before going to all of that, you put the staff in the cock on the plate to check the shakes? There can be variation in these so easier to find out before you've fitted it to the balance😁

It's becoming a big job but a great way to learn and practice these things👍

Cheers, Chris

j.allen · May 26, 2017

Jiminoz, I thank you for this chronicle. I have a beautiful staking set as well as a jeweling set. I have never gotten any real use out of them except to tighten a cannon pinion or make a small adjustment to a jewel when the endshake was not right. I'd like to get more hands on experience but have never had the opportunity. They just collect dust, but I do love vintage tools.

j.allen · May 26, 2017

I have a watch or two which I would love to re-staff. However I don't have a lathe and I'm not sure punching it out is the best option. If the hole in the balance is distorted it won't exactly be easy to replace or fix. These are 1940's movements.

Larry S · May 26, 2017

Wow ... deep end of the pool. I'm just happy to have found an affordable/competent watchmaker! Great article.

JimInOz · May 28, 2017

ChrisN
..........Now, I assume before going to all of that, you put the staff in the cock on the plate to check the shakes? There can be variation in these so easier to find out before you've fitted it to the balance😁.........................

No, I have to admit I didn't, I find it easier to manage the staff when it's in the wheel.

Which leads to the next question.

I checked for end shake in dial down and there is a noticeable movement upward toward the balance cock. I'm unable to measure it but just by looks and guessing, it could be 0.2/0.25mm, which feels too much to me.

I also noticed when removing the balance assy again that there are three small digs or gouges in the plate just inboard of the balance cock screw hole 😵‍💫.

After some research I found out that this is an old "watchmakers" trick to adjust end shake and they go by the cute name of "pig's ears".
A graver (or probably just the nearest screwdriver) is used to gouge up little hills in the metal either inboard or outboard of the balance cock screw hole, depending on whether you want to raise or lower the end of the cock.

So I have pigs ears that were done to increase the height of the balance cock and I have too much end shake with the new staff.

Would I:

1 - scrape the hills down to the original surface of the plate to reduce the distance,

or,

2 - Leave the pig's ears and adjust the height of the bottom jewel which could be a fraction under depthed?

As usual, any advice is welcomed and appreciated.

ChrisN · May 28, 2017

Hi Jim

Ah, the joys of watchmaking and finding the "tricks" that other people have done🙄

First, and it seems a silly question, but you do have the cap jewels in before checking end shake? If not, it will be huge, obviously, but we all do daft things sometimes.

If you really have 0.20/0.25 mm then it's about ten times what you want so, far too much. I'd measure the lengths of the two staffs you have and see if the other is a little longer as it would be easier to replace that staff again than anything else. At least with these, staff removal is easy so, you've lost nothing by fitting it to the wheel.

Possibly, the previous watchmaker couldn't get the correct staff so fitted a bestfit item and had to fix the end shake. Pigs ears is not the preferred way but, it's quick and dirty and obviously worked in this location for them. I've seen a piece of wax paper cut to fit under the balance cock which again is not ideal! It seems anything goes with some people. Out of interest, Poljot use factory steel shims to adjust endshake which fit under the balance cock in the same way as the paper did but, usually with a shock system, you'd move the lower jewel as you're proposing. I am not sure with the watch that you have if there is any adjustment in the lower cap jewel but it seems unlikely.

So, way forward for me would be:
1. Check the cap jewels are properly seated.
2. Fit the fork and this should have very little end shake.
3. Fit the balance and it should have a little more or about the same as the fork.
4. Have a look from the side where the fork end is in relation to the ruby pin - it should be more or less central in the height of the pin.
5. At the same time, see if the guard pin on the fork is in the middle of the safety roller - it should be.
6. Move the balance up and down and see if you still meet items 4 and 5.
7. Based on that, you can see which side of the shake needs to be reduced - for example, if you can move the balance up by adjusting the lower cap jewel, you may find that now the fork is clashing with the roller table and that's not going to work. Probably, you'll end up removing the pigs ears as that is what is not as designed.

I know you can read this so, here's a picture below showing what I mean. On the section is the main roller table at 0.2 mm thick with the ruby pin showing to the right of that and the fork is exactly mid height of the ruby. The guard pin on the fork is exactly mid height of the safety roller - well, that's where I drew them😁 but, that's what you're looking for.

Good luck!

Cheers, Chris

ChrisN · May 28, 2017

Not quite right for item 7:

7. Based on that, you can see which side of the shake needs to be reduced - for example, if you can move the balance up by adjusting the lower cap jewel, you may find that now the fork is clear of the ruby and that's not going to work. Probably, you'll end up removing the pigs ears as that is what is not as designed

JimInOz · May 28, 2017

Thanks Chris, I'm enjoying a wee dram at the moment so doing things that require fine motor skills and a clear head are best left until morning so I'll do some more detailed examination tomorrow.

Archer · May 28, 2017

j.allen
I have a watch or two which I would love to re-staff. However I don't have a lathe and I'm not sure punching it out is the best option. If the hole in the balance is distorted it won't exactly be easy to replace or fix. These are 1940's movements.

I personally would never punch a riveted staff out. The rivet does break off to an extent if it was made correctly, but there will still be a portion of the staff that is flared that will remain, and can distort the hole in the balance as you punch it through. I use a lathe and cut the hub off - this way the rivet actually stays put and you slip the balance off the other end of the staff, so the hole in the balance doesn't need to go over any enlarged portion of the staff.

If you don't have a lathe there are a couple of alternatives - one is grinding the hub off - they actually make little machines for this purpose but you may be able to do it with something like a Dremel or Foredom style tool, but this would require some very careful set-up, and there is risk involved for sure.

Now if the balance itself is not made of steel (if it's Glucydur or other non-ferrous material) a better alternative is to remove the balance spring, remove the roller, and dissolve the old staff out using an alum and water mixture. This will dissolve the staff and leave the wheel behind. But again you need to make sure there's no steel on the balance.

Cheers, Al

Archer · May 28, 2017

JimInOz
Would I:

1 - scrape the hills down to the original surface of the plate to reduce the distance,

or,

2 - Leave the pig's ears and adjust the height of the bottom jewel which could be a fraction under depthed?

As usual, any advice is welcomed and appreciated.

Would not call people who do such things watchmakers, but unfortunately it's quite common. I keep a very small Arkansas stone at my bench for removing these...

JimInOz · May 29, 2017

I used a fine graver to scrape off the hills from the plate and now I can see why they call them "pig's ears".

Balance end shake is now barely perceptible. Next step is to clean everything up again so no swarf or dust gets into the works and then try another test run.

Getting better bit by bit.

Deafboy · May 29, 2017

JimInOz
Getting better bit by bit.

👍