Expert: Martin Meyer - 1/8/2008

Question
I have a mantle clock that has a Hermle 340-020 movement and it is running quite fast. When I take the back off and look at the movement. I see at the top right a plus sign and a negative sign. Which I would assume means that a turn right is slower and a turn left means faster. There is a little screw just above that plus and minus sign that is on a long post with a pointed needle looking thing rested on it. This needle appears to be resting on this screw which is a standard flat head screw. The pointed needle appears to be attached to a round spring looking gadget. Do I turn this screw to slow it down?

Answer
Hi Rich,
    You're correct in every respect. You turn the screw counterlockwise to make the clock run faster, and clockwise to make it run slower. The stamping with the + and - signs probably also has two lines drawn through a screw head symbol, with "10 S/d" printed inside the arc of the two lines. This indicates that a turn of the amount shown by the arc will change the fast/slow setting by 10 seconds per day. I would consider this to be only an approximate starting point; the proof is in the actual running of the clock.