Service and Repairs of a Salmon Hettich Clock Movement.

This movement is from a Bahnhäusle style mantel clock circa1870. It is a good quality movement attributed to Salmon Hettich of Schonach. 

It is an 8 day movement, with a count wheel striking train. The count wheel is internal and is fitted on the winding arbour behind the barrel. It has a silk suspension system, adjustable via a small thread length adjuster on the pallet cock.The steel used in the movement is of very good quality, very hard, which makes the pivots hard wearing. 

There was evidence of previous repairs to the movement, however there has been no previous bushing of worn pivot holes. This was completed where necessary, but not shown here. In the picture below it can be seen that some replacements parts have previously been added. These include a new going train ratchet wheel and pawl. The pawl and ratchet wheel are rather crude, given the quality of the movement. The brass ratchet spring can be seen to be broken. Compared to the spring on the strike side, it is shorter. 

On the time side the pawl's end can be seen to be broken off. Though not easily seen, the teeth of the ratchet wheel, are quite worn along their tips, closet to the front plate. All of these will be replaced, and will require fabrication. 

Below is a picture of the movements escapement anchor, of the recoil type. Two deep wear ruts per impulse face can be seen, which illustrates that the anchor has been moved along its arbour in order to offer up fresh parts of the impulse faces to the escapement wheel teeth. So, moving the anchor to attempt to offer fresh parts of the surface is not achievable. A new anchor will need to be made from tool steel gauge plate. Thankfully the 'silhouette' lines of the anchor are intact, so in this case it is possible to stick the old anchor to the gauge plate steel and scribe lines for a new anchor. The anchor was then cut out off the gauge plate and hand finished. 

The new anchor comes on and off its arbour and in and out of the movement many times during its fabrication, as one tries to  ensure the correct span and drops are achieved. Once all is correct it was hardened, and the impulse faces polished to a mirror finish. 

                               

For the new ratchet wheels, a wheel cutting tool was made from a piece of lathe tool steel. It was formed to closely resemble the original teeth. Though not perfect copies of the original teeth on the new ratchet wheels, I was happy they were close enough and would function well. The wheels were cut on a small mill, and in truth I was a little niffed with myself for not cutting the two wheels together in one go, a lapse in practical thought. 

New pawls were hand cut out of plate steel steel, finished, hardened, tempered and blued.

A little more tricky was fabricating a new click spring from brass. I chose to mill one out from a piece of brass stock, and finish by hand. The first picture below shows the spring milled out in the rough as it were, ready to be cut off and finished.

Below you can see the completed spring on the right, a mirror image of the strike train click spring.

Below you can see the new wheels, pawls and click springs together, with the old components above them. These new parts will bring the movement back to looking like it should.

Once all the work was completed, the movement assembled it went on to test and ran very well with its new escapement anchor.

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