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..

With a watch key set watch this stage is probably not required.

Using the flat end of the tweezers or some other tool gently press the hand onto the cannon pinion, a rocking motion from 6 towards 12 o'clock (this direction to avoid bending the minute hand) is generally easier than trying to press straight down. If you had to keep hold of the other end of the hand to keep it in place then let it drop as pressure is applied to avoid bending the hand. Some people may find using 2 pairs of tweezers easier - if you have 2 pairs! Approach from 6 o'clock as in the photo if possible but it is not critical at this stage.

It is possible to do this with a finger which has the advantage of better "feel" but there is an increased risk of pending the minute hand down near the hub.

The hand will now be on the pinion but may not yet be secure, the next stage is to press it home.

Key set watches: put the key onto the cannon pinion as you would for setting and press the hand into position.

Keyless watches: This is the potentially "dangerous" bit because if you slip you could bend or break the minute hand so it is important to do it the right way.

The idea is to use the edges of the tweezers positioned either side of the cannon pinion to press the hand into position. If using tweezers rather than a tool from a staking set I would not use the point of the tweezers as in this picture but further back so that the figure is over or closer to the cannon pinion but that is impossible to photograph clearly, at least single handed.

Approach from 6 o'clock so that if you slip the tweezers will miss the hands and don't press harder than is necessary to get the hands on as this increases the risk of slipping and increased damage caused if you do slip, also you don't want the minute hand pressing hard against the hour hand at the hub or the watch could stop or run with poor amplitude causing various problems.

If the case is open faced and has a hinged front then you will probably not be able to approach from 6 o'clock, removing the movement from the case is not recommended as there is a risk breaking the balance staff if you make a mistake, so the best thing to do it to approach from 12 o'clock - carefully!

When finished make sure the minute hand clears the hour hand, the hour hand clears the seconds hand and the minute hand is low enough not to brush the crystal when fitted, on a hunter the clearance is likely to be very close so take care. If the hands have been bent then they will need to be reshaped with the tweezers.

Replace the bezel and the job is done.

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