Expert: Martin Meyer - 2/13/2008

Question
a clock repair shop in Los Angeles put in a new Franz Hermle 350-020 movement in a 30 year old Seth Thomas mantle clock.  It just started running a couple of minutes slow per day.  there is a speed adjust screw on the top right of the rear of the movement.  It has a + on the left side (9 oclock) and a - sign on the right at 3 o'clock, but it also appears to have an arrow pointing cw below the + and one pointing ccw by the -.  This makes me think to speed the clock up, I need to turn the adjustment screw cw.  is this correct?  Thank you

Answer
Hi Ron,
    Hermle could have made that particular marking system less confusing. You are correct: you turn the screw counter-clockwise to make the clock run faster. The longer lines passing through the screw-head symbol describe an arc below the screw-head symbol. Inside this arc is "10 S/d". This is intended to show that a turn of the screw in the amount of that arc will change the rate of timekeeping by 10 seconds per day.