HAC/HAU movement servicing

The arrangement of the gears should be familiar to anyone working on German clocks made in the first quarter of the twentieth century

Bought on an online estate auction site earlier this year, servicing the movement is the subject of this post. Once the movement is serviced, the next step is to address dirt and grime on the case and see what I can do to improve the look of the dial although I am not very hopeful that I can do much to improve it.

For those unfamiliar with the HAC acronym, it stands for Hamburg American Clock Company, a well known German company acquired by Junghans in the late 1920s. It is otherwise known as Hamburg Amerikanische Uhrenfabrik or HAU. Kind of a strange name for a German clock company but that is how the original investors wanted it named.

I have a number of German clocks including familiar makers such as Junghans, Mauthe, Hermle, Jauch, Gufa, and Gustav Becker but this is the first HAC clock in my collection.

HAC clock
HAC clock circa 1900-1910

Assessment of the movement

It is a typical 14-day German time and count-wheel strike circa 1900 to 1910. It is a robust and almost industrial looking movement and perhaps made early in this series of movements. It could be the type #21 although I can find nothing to confirm it.

The arrangement of the gears should be familiar to anyone working on German clocks made in the first quarter of the twentieth century. This movement has slightly thicker plates, no cutouts, and no extraneous holes and looks sturdy.

HAC clock movement
HAC clock movement, dirty and very tarnished

It has been worked on in the past, the strike side mainspring having been replaced at some point in the clock’s life. The time side has the HAC cross arrows stamped on the mainspring and appears to be original.

HAC clock movement
HAC clock movement, no cutouts

It doesn’t look as though there were issues at the time when the mainspring was replaced, no punch marks around the pivot holes or new bushings, for example, but there are wear issues now and that is to be expected in a 100+ year old clock movement.

In total the movement required 9 bushings, 6 on the strike side and 3 on the time side; 4 on the backplate, and 5 on the front plate. A couple of pivot holes are questionable and exhibit some wear and out of an abundance of caution I bushed them and why not while I have the movement apart. As expected there is more wear on the lower parts of the trains.

The bushing work went as expected. Some of the pivots are quite small and required 2.50mm OD bushings which I don’t often use but have plenty of them in my supply.

Ultrasonic cleaning did not do much to brighten up the brass plates, but to me aesthetics is unimportant. My goal, as always, is simply to have a properly serviced movement that runs well.

Assembly and testing

The movement was assembled and oiled. Both the strike and the time side are running well. There were no particular problems setting up the strike side other than a couple of attempts setting up warning before I got it right.

HAC movement
HAC movement on the test stand

It continued to run well during the next couple of weeks.

It is a 14-day movement but I find with these German movements that winding them once per week ensures more accurate timekeeping.

2 thoughts on “HAC/HAU movement servicing

  1. I have HAC clock with an identical movement. As my clock skills are very new I have only surfaced cleaned it and very lightly oiled the pivots. It maintains good timekeeping and looks and feels very well made. It’s accurate timekeeping is only matched by a much later, 1976, St James Hermle clock I also have.


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