Expert: Martin Meyer - 12/1/2008

Question
I have a grandfather clock that is running fast. How do I adjust the time. I believe it has something to do with the pendulum?  Thank You

Answer
Hi John,

You adjust the timekeeping rate by turning the regulating nut at the bottom of the pendulum, just below the disk. You should turn the nut to the left, i.e., lowering the nut on its threaded rod, to make the clock run slower. It is important to note that it is the position of the disk, not the nut, which controls the rate of the clock. Pendulum disks are sometimes tight on the pendulum rod, so you must make sure that, when you turn the nut down, the disk also moves down to rest directly on the nut. This sometimes requires gently pressing down on the disk while you hold the pendulum rod firmly above the disk. Be certain that you do not pull down on the entire pendulum, or you might break the suspension spring which attaches the pendulum to the clock.

The amount that you should turn the nut varies due to a number of factors, so there is no set rule for how much to turn it. I would recommend starting out by turning the nut one turn for each minute per day that the clock is off by. Don't forget to reset the clock to the correct time after each adjustment, or you will compound the amount of error. Always check the clock against the same reference clock; this should be either a plug-in electric clock or a quartz wristwatch. Do not use a mechanical clock, a quartz (battery) clock, or a radio or TV announcement, as these are not always accurate.  http://www.clockmasteronline.com