Restoring a Silver Watch Case

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version.

A while ago I posted a description of how a watch movement is cleaned, in this post I explain how I restore a silver watch case. The case in question was made by John Woodman of Smith St, Northampton Square, London in 1888.

From the wear pattern you may be able to see that the back of the case is depressed, there is also a dink bottom left and there is a lot of pocket wear, in reality it actually looks worse than in the picture. So something had to be done.

The first stage is to get rid of the worst of the muck and oxidisation, this is done with silver polish and a glass fibre brush.

If this were not done the next stage would not work as effectively and the fluid would have to be changed more frequently, perhaps after each case.

The ultrasonic cleaning is primarily to get into the parts other processes cannot reach including into digs and scratches. The fluid bath is detergent based and the case will stay in for 30 minutes which seems about optimal for a silver case.

The second ultrasonic machine shown is loaded with a solvent based cleaner that I use for cleaning movements.

The next stage is to press, rub or hammer out the back and the dents. This process will be different depending on the way the case is made and any finish such as engine turning on the back. Swiss cases in particular are sometimes made with a bezel similar to that on the front with a silver disk inserted - if you press on that to hard it will come out and be a devil to get back in and it you hammered the edge probably impossible.

It is better to press or rub rather than hammer as it will cause less damage to the inside which is difficult to burnish out due to the shape of the case and the necessity of preserving the hallmarks. The amount of work done on the outside has therefore to be balanced with the amount of damage to the inside and possible distortion of the case which may or may not be readily correctable.

The picture above shows the case after this work, the dink still visible but it is now more of a scratch or dirty mark.

For a case with a smooth back now comes burnishing with increasingly finer abrasives. A balance has to be struck between the amount of silver removed compared to the gain achieved in appearance and possible loss of structural strength.

In general I do not try and take out all of the marks but to still give a nice finish. All of this is done by hand.

Ten Louis Brandt and Frère - Omega & Labrador watches.

In the last couple of months I have been able to buy in more "Omega's" than I normally would expect to get in a year, here are most of them, 2 at Brackley missed the group shot. They vary in size from approximately English size 10 to a rare size 18. 

They date from 1897 through to 1922 and all are essentially the classic François Chevillat 1894 designed Omega movement and have 15 jewels with a Breguet sprung cut compensating balance with double roller.

Two from 1900 are unusual in that they carry the Omega name or Logo but have screw mounted jewels on the top plate and a screw micro regulator and are therefore the higher grade Labrador in all but name, but this is before LB&F changed the company name to Omega.



 

The Safety Pinion (Fogg's patent)

A Reversing Pinion prior to assembly.

The Safety Pinion originated in 1865 when it was usually described as "Fogg's patent", it was intended to avoid damage to the movement in the event of a mainspring breakage, the spring being let down too quickly during maintenance or following failure of the click (ratchet stopping the mainspring arbor from "winding down" and forcing the barrel to move instead).

The problem was that with the very strong springs required at the time the backlash after a failure would go through the train and potentially break weaker parts, mainly I suspect the lever pallet and pallet jewels.

The solution is quite ingenious. Instead of the centre wheel pinion being fixed to the wheel / staff it is screwed on. In normal use the gear teeth on the mainspring barrel bear against the pinion and keep it screwed down.

A "Reversing Pinion" during assembly
but not yet screwed on.

If the pressure is suddenly reversed the pinion unscrews and no reverse power is applied to the rest of the movement.
This solution was initial used by Waltham and then by Elgin who presumably licenced it, but by the 1890's, if not earlier, the concept was more widely used in the USA (the example shown is from a Seth Thomas of 1896) and by a number of the larger makers in England including The Lancashire Watch Company and William Ehrhardt.

Waltham later introduced the "Safety Barrel" to address the same problem but as the amount of power a watch required reduce with the introduction of lighter movements, improved manufacturing tolerances and more jewelling, there was no longer a real need and safety pinions were discontinued.

Slow train, fast train

No not about railroad watches as such but about the frequency at which a watch balance turns. By the middle of the 19th century lever watches were pretty much standardised at 16,200 vibrations per hour (VPH). As watches got smaller and engineering tolerances got tighter makers started to move towards a faster beat of 18,000 VPH, usually referred to as a "Quick Train".

As usual the Americans moved first with Waltham changing the beat of their size 18 full plate 1877 model to 18,000 after launching it at 16,200 and the Illinois Watch Company changed quickly in about 1879.

The conservative English trade were, as usual, quite a way behind probably not helped by the investment required in redesigning their watches to change the gearing in the train and retooling costs which would have been more significant for the much smaller English companies than for the large American operations.

Generally it was the early 1890's before the Coventry and Lancashire trades started to use the faster train, led not unnaturally by newly introduced keyless three-quarter plate designs with some of the older full plate designs being allowed to die a natural death, particular Fusee movements,  and others being changed mid life or when Swiss Lever escapements started to replace the English Lever.

The London trade were even more conservative with some makers, notably P & A Guye and J.W. Benson persisting with the slower train up until around about the first World War. The lovely Benson Ludgate pictured was made in 1912 still running at 16,200 which does give it a very nice "majestic" tick.

Wrist watches, as one might expect, continued the development and my 1980s Rolex runs at 19,800 VPH with later ones running even faster.

Waltham Display Case

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As described in some detail in my post "the standard watch case" buyers could at some retail outlets configure their own watch by selecting a case, movement, dial etc. and then to have the watch assembled for them on the premises

The Waltham display cases as shown here could be used to display a selection of movements to help the customer decide. I suspect the hole in the base was used to bolt it down to stop people making off with a potentially valuable movement.

Now this type of case can be used to simply display the movement or to use it as a desk watch.

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The back of the case has a second crystal so that the movement, in this case a 17 jewel Waltham 1908 P.S. Bartlett from 1918, is visible.

A Double Own Label!

A 16J Errington, 1895.

At first sight this appeared to be a normal "own label" watch made for by C.H. Errington of Coventry for Curtis & Horespool of Leicester.

However looking at the hallmarks there are normal marks for Chester 1895 but one set of makers marks have been over-stamped by another.

Under high magnification and with a hint from another mark (see below) it is possible to read the second set of marks as belonging to Alfred Moss Jacobs & Co (Watch Makers), 18 Cross St, Hatton Garden, London.

The original marks are probably those of Errington.

Whats in beat?

A Swiss lever escapement

If you have ever set up a pendulum clock you will know that it is important to level the movement so that the pendulum swings equally to the right and left of a centre line that is perpendicular to the base of the movement, this will help in timekeeping, make the clock easier to start and, if it is driven by a spring, it will be less likely to stop as the spring gets closer to being fully wound down. It will also result in a nice even "tick - tock". 

It is the same with a watch except that it is now the balance wheel which has to swing an equal amount left and right from it's "in beat" position  - which for a Swiss Lever escapement is when the impulse jewel, balance staff and the lever pallet arbor are in alignment with the movement at rest. Its a little more complicated for an English lever with the pallet tangential to the escape wheel.

 

Before the advent of electro-mechanical and now computerised escapement analysers watch makers and repairers had to adjust  watches to be in beat by visual alignment and listening to the movement through a type of stethoscope, it is impressive how they achieved the accuracy that they did but some errors are fairly easy to detect by listening to the watch.

 

This is my Waltham 1899 Riverside Maximus from 1901, the movement is 0.3 milliseconds (mSec) out of beat which at a nominal rate of 18,000 vibrations per hour (VHP) is an error of 0.17% - that is as close to perfect as you are likely to hear from a 114 year old watch so run the video to see what it sounds like.

 

 

The next video is of  a job in process and the movement is currently out of beat by 2.1 mSec or 10%, run this video and you should notice the arrhythmia.

Correcting an out of beat movement is likely to be a combination of reforming or tweaking the hairspring (in this case it needs major reshaping due to previous tampering and there is a real possibility of work hardening causing the spring to break when adjustments are made), turning the roller or preferably the hairspring collet on the balance staff to improve alignment and possibly some adjustment of the banking for fine tuning.