Adjusting the Pendulum on Your Grandfather Clock

Did you know that the length of the pendulum is what decides how fast or slow your grandfather clock is keeping time?  It must be adjusted properly to keep accurate and proper time.

  • The longer you make the pendulum, the slower the grandfather clock keeps time.
  • The shorter you make the pendulum, the faster the grandfather clock keeps time.



You must move the pendulum bob up or down to adjust the speed of the clock.  You accomplish this by turning the nut at the bottom of the pendulum.  Moving it up pushes the “bob” (the round disk) up so the clock will run faster. Turn the nut in the opposite direction to lower the “bob”, and set the clock to run slower.

grandfather clock pendulum


Adjusting a grandfather clock takes patience.

First you must see how far off the clock is from the accurate time.  This is easily accomplished using your cellphone.  Watch your phone time and as soon as it advances to the next minute on whatever hour it is on, set the minute hand on the grandfather clock to that location.

Now wait 24 hours.  Is the clock fast, slow, or on time?  Move the nut on the pendulum up or down depending on if it is fast or slow.   A full turn equals about a minute a day.

Look at your grandfather clock again another 24 hours later and see if it is fast or slow. If you need to, reset the minute hand to the correct time and move the nut up or down again.  About a 1/2 turn for 30 seconds a day.

This is where the patience part comes in as you may need to repeat this process over a course of several days to make sure that the pendulum is the correct length and that the correct time is achieved.

grandfather clock Regulation_diagram
If you have done this and your clock is still not keeping accurate time contact Valley Clock Shops as your clock may need further oiling, cleaning, or repair.

Comments are closed