Hamilton 940 Escape Wheel

[Bruce W Sims]

Hi, Folks:
Reassembling my 940 I am taking some exra time to check the diameters of my pinions as I think I may have inadvertantly mixed some parts from another project.
Oddly enough I noticed a bit of variance in the escape wheel and compared it to a spare that I had from a Donor watch. Note that the item on the left has considerable more distance between the wheel and the pinion though the staves are of the same
length. AFAIK the wheels are secure in their positions but frankly I am not sure which
wheel I should use. I believe the clearance above the pallet fork is the same for both of them. Any thoughts how I can decide which is the better assembly candidate?

Best Wishes,

Bruce

 

[Skutt50]

Is the overall length the same for both?
Is the wheel diameter the same for both?
Are the pivot diameters the same for both?

You can always install one and see how it interacts with the pallet fork and the fourth wheel.
If both seems fine try them both and keep the one that gives you the best readings on your timing machine.

 

[Dave Coatsworth]

It's a bit hard to tell from your photos, but the 940 escape wheel would have conical pivots. The lesser grades have straight pivots. Do both wheels have conical pivots?

 

[Bruce W Sims]

OK...have some stats and new photos. Overall length of the staff for one wheel is
4.45mm while the other is 4.37mm. Pivots are .14mm all the way around. The wheels,
themselves turn on the staff as they seem to be set in a sort of brass bushing through
the hub of the wheel while the pinion is quite firmly set in place. Three questions then:
1.) Ought I use the wheel with the shorter staff to allow for greater end-shake?

2.) Can/need I move the wheel to approximate the same length as the lower end of the pallet fork staff?

3.)Is it necessary....of even possible...to peen the brass so as to hold the wheel in position on the staff, without damaging the wheel or pinion, using my staking set?

dave: This is about as clear as I can get it but I can't say I am altogether sure what I am looking for that would make the pivot
"conical". Does this help?

Thoughts

 

[Skutt50]

Try to install the shorter wheel and check the end-shake. If it is moving up/down excessively, try the other wheel. You want a small end-shake.

The wheel should not spinn but be fixed to the arbor. The pinion is typically cut from the same piece of steel as the arbor so, no spinn there. Often the pinion has a small sholder where the escape wheel is fitted You could try to re-fit the escape wheel and then rivet it slightly by "folding" the sholder over the wheel. This is best done with the staking tool.

When installed, the teeth of the escape wheel should be about centered to the jewels in the pallet fork. Since the pinion is at a fixed height the escape wheel, when fitted, should be at the correct height.

If the escape wheels are fitted at different heights this could be used as a way of figuring out which of the escape wheels that belongs to the movement.

 

[Bruce W Sims]

Thanks, Skutt..... I had used my staking kit to install the Balance Staff so I have some insight into riveting. My strategy for this escape wheel was to rest it in the staking tool
bed so all the energy from working the center of the wheel would be taken by the pinion. I intended to use the smallest round
punch that slips over the shaft. However, I also considered a slightly larger round punch
so as to move material towards the staff. Any thoughts on this thinking?

 

[Skutt50]

I probably would remove the wheel and close the brass fitting slightly in the staking tool.
Then re-fit the wheel and press it down to the proper position on the arbor.

I use a rounded punch for closing a hole.

 

[Dave Coatsworth]

This is about as clear as I can get it but I can't say I am altogether sure what I am looking for that would make the pivot
"conical". Does this help?

That is a conical pivot. A 'straight' pivot would be exactly what the name implies - straight. Not the conical shape of the pivot in the photo.

 

[Bruce W Sims]

Thanks, Dave...... I was also wondering if those are worked differently during polishing.
Judging from the videos I have seen, the technique of using, say a JACOT would tend to take any contour out of the pivot.......or am I thinking about this wrong.....?

 

[Bruce W Sims]

I probably would remove the wheel and close the brass fitting slightly in the staking tool.
Then re-fit the wheel and press it down to the proper position on the arbor.

I use a rounded punch for closing a hole.

Well..... I did dismount the wheel from the shaft....quite easily. I gave the brass a tap with a round punch.....and then had quite a time remounting the wheel, needing to poise the wheel as remounting caused the brass hub to deform with the re-introduction of the shaft. AFAIK the wheel is firmly mounted and the rim of the wheel is true. Now to mount this and see whether the longer or the shorter staff is the better choice.......

 

[gmorse]

Hi Bruce,

Judging from the videos I have seen, the technique of using, say a JACOT would tend to take any contour out of the pivot.......or am I thinking about this wrong.....?

I expect the videos you've seen of the Jacot tool have shown its use on straight pivots with square shoulders, for which a burnisher with sharp edges is necessary. However, the proper burnishers have one edge slightly radiused to avoid forming a ridge where the conical part begins on conical pivots on balance staffs and escape wheel pivots such as yours. The angles of burnisher edges aren't exactly 90º, they're a parallelogram, (or should be), to allow the burnisher to work fully into the shoulders, and because of this they come in two varieties, a left-handed and a right-handed. To decide which one you need, you first need to decide whether you'll use it on top or underneath the work; on a Jacot tool you have to use it on top. You also need to decide whether you use the tool with the beds on the left or right; the picture of the tool in its case is the opposite way round to the way it's mostly used if you're right-handed, ie, with the pulley on the left and the beds on the right. Using this tool with the beds on the right, as in the middle picture, and the burnisher on top, you would need a left-handed burnisher.

When you're burnishing conical pivots, you must be careful not to put any pressure on the unsupported conical part, possibly resulting in a broken pivot, and there's a special guard, (missing from most second-hand tools), which is designed to prevent this. The cone is polished during the turning in the lathe, not in the Jacot tool, which only works on the parallel portion of the pivot.



Regards,

Graham

 

[Skutt50]

I gave the brass a tap with a round punch.....and then had quite a time remounting the wheel,

Easy does it. It is better to use several light taps and test several times on the arbor, to avoid overdoing it.

 

[Bruce W Sims]

Thank you for take the time to lay that all out. In fact I have a version of a JACOT
which I had originally intended for polishing pivots, but your response is exactly why
I have not put it to work. The version I have was purchased used and is the version that does Not have the arrangement necessary to drive with a bow.

BTW: I have also been in the market for a HORIA tool after seeing one used to adjust
the position of a wheel on its staff in a YT video. The Swiss items are costly as are the
items on EBay. However there is a clone from the PRC through ALIBABA for about
$100USD. Seems to come with all the stumps, etc. Here's me thinking they were only for jeweling. Thoughts?

Best Wishes,

Bruce

PS: I'm including a photo of the JACOT version I have.
Note: Absence of wheels and pullies ....... oh....and the tools have obviously been badly handled.......sheesh....

 

[gmorse]

Hi Bruce,

The version I have was purchased used and is the version that does Not have the arrangement necessary to drive with a bow.

These are not uncommon and are used with a split pulley fitted directly onto the staff which allows it to be driven with a bow. I have to assume that whoever owned this in the past had no idea what it was for or how to use it!

I have no experience of the Chinese Horia clone tools, but DeweyC has experimented with one I think. I use a Favorite jewelling press for that sort of work.

Regards,

Graham

 

[DeweyC]

Hi Bruce,


These are not uncommon and are used with a split pulley fitted directly onto the staff which allows it to be driven with a bow. I have to assume that whoever owned this in the past had no idea what it was for or how to use it!

I have no experience of the Chinese Horia clone tools, but DeweyC has experimented with one I think. I use a Favorite jewelling press for that sort of work.

Regards,

Graham

Graham,

I have and do use the clone of the Horia jewelling press stumps. They are an exact fit into the Horia 4X4 press and serve quite well. These are now selling with the press (which I would think worth trying) for the price I paid for the full set of pushers/stumps.

FWIW, this is the tool I use for removing and replacing jewels in pocket watches as well as for replacing rollers and balance springs and such.

 

[Bruce W Sims]

Thanks, Dewey.... what caught my attention was the micrometer build into instrument where I don't remember seeing the jeweling presses (see: Seitz). I will assume the knurled knob under the press handle serve a comparable purpose. Frankly after hearing how the lathes from the PRC do not work with WW colletts, I was a little leary. Thank you for soothing my troubled brow.......

Best Wishes,

Bruce

Graham: I remember that you expressed the opinion that De Carlo was a bit dated and I have taken to using his book (see: "Practical Watch Adjusting"). What are your thoughts on his approach to fine adjustment
with vintage watches? Just wondering.....