Friday, 29 April 2016

J.W. Benson Sales Catalogue - Part 1.

I recently obtained a J.W. Benson sales catalogue, unfortunately the first 8 pages are missing but with so little information available on the company, and much of what is available contradictory, it is worth spending time analysing what I do have.

The first thing to do was to date it, this was not as easy as hoped for, many of the watches shown were in production in one form or another for c 50 years and in any case there are unfortunately very few pictures of the movements to aid dating. It soon became clear that this 67th edition makes use of text and pictures that span many years. 
One movement is engraved “By Warrant to H.M. the late Queen Victoria” which I have previously only seen on movements from 1901/2 to c 1907 and there were extensive quotes from the 7th edition of the Royal Geographical Societies “Hints to Travellers” which was published in 1893 but superseded by the 8th edition in 1901 and the 9th in 1906.

Yet the Swiss watches shown are from their style and size are clearly much later, nor are they from the makers I have seen resold by Benson prior to 1910.

The give-away was a partial view of the movement of their Swiss “Greenwich Watch”, this is an exact match to the Tavannes Hunter movement, the earliest datable examples I have come across of this movement branded by Benson are from 1931/2 (probably 1932) prior to which the Swiss watches were generally by Revue and before that Longines.  Based an a large number of these movements I have seen the technical description of the "Greenwich" also implies a production date of 1936 or later. 
So the catalogue is from the 1930’s Bensons having been bombed out in 1941 with, according to the bombing report the loss of 12,000 watch movements, and they are unlikely to have produced a catalogue in 1940 or 1941, particularly offering an 18 carat gold Swastika fob medal (75/- or £240 in todays money[i] ).
J.W. Benson (Tavannes) 15J
half hunter, 1940.

Elsewhere there are hints that the catalogue is probably from the late 1930s, for instance it is unlikely that Bensons would have offered a Swastika medal prior to the Nazi party coming to power in January 1933, or that an example engraving would be dated January 1937 much before that date.
I think therefore that it is reasonably safe to date the catalogue from between 1935 and 1939 inclusive and certainly no earlier than 1932.

[i] Assuming a date for the catalogue of 1935.

Saturday, 23 April 2016

Waltham 1908-Riverside.

This is one of a series of posts illustrating the main grades of Waltham size 16 watches, in this case the 1899 & 1908-Riverside.

Waltham 1908-Riverside, 1908
This following description is from an advert of 1913:

Tuesday, 19 April 2016

Replacement Watch Keys and Sizes

It is unfortunate but modern Indian made keys are numbered differently to old ones, the tables below shows the conversion from one to another and the size of each.

If you have a watch but no key then usually the easiest thing to do is to buy a complete set of 14 modern keys which can usually be found for less than £6 by searching eBay or on Google etc. Individual new keys are available but the price difference is small so it is probably safest to buy a set and be sure of getting the correct size.

As a general rule antique keys are easier to use as normally there is a swivel between the ring and the body of the key which makes it generally easier and if on one end of a double albert it avoids twisting the chain as you wind. You may also be able to find an old tube like key which is adjustable for different arbor sizes.

If purchasing an old key you will find that relatively plain keys will normally be cheaper than those with advertising or a makers name on them.

"Spider" keys are also available with a number of keys radiating off of a central hub but these are expensive and really only of benefit if you have a large number of watches, or restore them.

There are a few things to be aware of:

1. Old keys tend to stretch and wear with use so if your existing old key was not original to the watch then the equivalent modern watch key may be a bit small and buying an old key without being able to test it can be a problem as it may be too big.

2. The winding and setting arbours on the watch should normally be the same size but may not be if one has been replaced as part of a repair or one is very worn, it is however sometimes possible to use a compromise size.

3. The modern keys have a bevelled entry into the key, this makes it easier to locate the key on the arbor BUT I have found that frequently this prevents the key from properly engaging when trying to set the time on a front set watch due to the setting arbor being to short above the hands if this happens it is necessary to file or grind the bevel off of the key which is quite straight forward as the metal is fairly soft.

 Watch Key Conversion:

   Modern   English 
             00           12
               0            11
               1          10
               2           9
               3           8
               4           7
               5           6
               6           5
               7           4
               8           3
               9           2
              10           1
              11           0 
              12         00 

Watch Key Size:
UK: 00 = 0.95mm.....Indian: 00 = 2.00mm
UK: 0 = 1.00mm.......Indian: 0 = 1.90mm
UK: 1 = 1.05mm.......Indian: 1 = 1.80mm
UK: 2 = 1.15mm.......Indian: 2 = 1.75mm
UK: 3 = 1.20mm.......Indian: 3 = 1.65mm
UK: 4 = 1.30mm.......Indian: 4 = 1.60mm
UK: 5 = 1.40mm.......Indian: 5 = 1.50mm
UK: 6 = 1.50mm.......Indian: 6 = 1.40mm
UK: 7 = 1.60mm.......Indian: 7 = 1.30mm
UK: 8 = 1.65mm.......Indian: 8 = 1.20mm
UK: 9 = 1.75mm.......Indian: 9 = 1.15mm
UK: 10 = 1.80mm.....Indian: 10 = 1.05mm
UK: 11 = 1.90mm.....Indian: 11 = 1.00mm
UK: 12 = 2.00mm.....Indian: 12 = 0.95mm

Sunday, 17 April 2016

Fitting a minute hand

Before opening the front bezel - in the same way as the back, either by screwing it off (use a rubber or  latex glove if it is stiff) or using a knife - clear a workspace and work over a white sheet of paper so that if the seconds or minute hands drops off you will be able to find it again.
References to key set watches are to those which are set from the front, those that set from the back such as a Benson Ludgate are treated as a keyless watch.
The only tools normally required are a strong pair of tweezers and a knife to open the bezel. It is possible to use side snips or other tools in place of tweezers but generally this is not recommended. It is perhaps easier to do this with the watch stopped but it is not essential. With a key set watch tools are probably not required, just the key. A loupe, bench magnifier etc. will make things easier.

A hand may come off of a watch for a number of reasons, the watch being knocked or suffering a lot of vibration, perhaps in the post, or the hand being brushed whilst setting a key set or open faced lever set watch. The hand may not come off immediately but if it is depressed a little - a common result of pressing on the flexible acrylic crystal of hunter type watch - then it may later come into contact with the hour hand and either stop the watch or be lifted off.

I suspect that rapid changes in temperature may make a hand more susceptible to coming off and a newly restored watch is more susceptible than one which has not been cleaned or disturbed for years. Being sent through the post is probably going to put the most strain on it.

A front key set watch with a square
topped cannon pinion to take the hand
and the setting key.
The minute hand fits onto the cannon pinion (see my blog entry on slipping cannon pinions for pictures of the cannon pinion and motion works below the dial), usually the top of the cannon pinion will be flush or close to flush with the top of the centre wheel arbor as shown in the two examples here.

On a few, mainly Swiss, watches the centre wheel arbor is hollow with a pin through it which protrudes above the cannon pinion, even though it will appear that the minute hand attaches to the pin is does not, there will be a hole in the minute hand for it to go through but there will also be a circular ridge under the hand which fits to the top of the cannon pinion - if the pin did hold the hand it would not be possible to adjust the time.

Before fitting the minute hand make sure that the hour hand is fully down, reasonably parallel to the face (top picture) and clearing the seconds hand.

Position at 12
First set the hour hand to twelve o'clock.

Key set watches only: If the watch is key set and the hour hand has been moved you will first need to line things up as the minute hand can only go onto the arbour in one of four positions, loosely fit the minute hand - which should be easy as the square cannon pinion top is tapered - set the minute hand to 12 o'clock then carefully adjust the hour hand to point at an hour using tweezers close to the centre. It is assumed that the hour hand will move fairly easily or it would not be displaced but if it does not move easily lift the hour hand off with a  removal tool or with tweezers underneath the central hub and reposition.

Position the minute hand onto the cannon pinion as shown, pointing to 12 o'clock..

Saturday, 2 April 2016

Elinvar Hairsprings

A cut compensating balance on an
Illinois Watch Co "Bunn Special"
Railroad watch.
Click on the image for a larger view.
One of the big problems in making a watch run too time is the effect of temperature on the steel hairspring, the biggest problem is not with respect to expansion or contraction (although that is an issue) but with the change in it's springiness (it's modulus of elasticity). On more expensive watches and clocks this was for many years addressed by the use of the cut compensating (or compensation) balance which reduces in size with increased temperature compensating for the weakening of the balance spring.

This was achieved by making the balance with two bimetallic rim sections with steel on the inside and brass on the outside. Moving or adjusting the screws let into the rim would vary the amount of compensation.

In the late 1890's a new alloy known as "Elinvar" was devised by Charles Édouard Guillaume (who got the 1920 Nobel prize for physics for the development of this and Invar a slightly less effective alloy), its key property was that unlike steel its modulus of elasticity did not change with temperature. When used as a hairspring it removed the need for a compensating balance.

A screwed balance on a Swiss watch
by Tavannes for J.W. Benson.
Many makers, particularly in Switzerland, quickly  implemented the Elinvar hairspring with a screwed balance replacing the expensive compensating balance.

The screws were retained to allow the balance to be balanced fairly quickly(as a car wheel with a new tyre) and the weight and number of screws could be used to adjust the moment of inertia to match the hairspring to make the watch run too time, for fine tuning and, when adjusted asymmetrically,to make small corrections to remove positional timing errors, for example when the watch was pendant up compared to face up.

Modern mechanical watches use the same approach although with different alloys.