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Adjusting the Pendulum on your Grandfather Clock

How to make your grandfather clock keep good time.

Adjusting the Pendulum on Your Grandfather Clock

How to speed up grandfather clock or slow down your grandfather clock.

The pendulum length dictates how fast or how slow your grandfather clock will keep the proper time. If you take time to adjust it properly, the grandfather clock can keep exceptionally good time for a mechanical timekeeper. Most newer clocks use a metal pendulum which are very stable.  Most older and reproduction clocks use a wood stick pendulum which can also keep good time if used in an area where the temperature and environment is stable.

Adjusting the speed of the clock is accomplished by moving the pendulum disk (bob) up or down.

Speed UP (turn nut left to right)——Slow DOWN (turn right to left)

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

This is adjusted 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. If you turn the nut as to lower the “bob”, the clock will run slower.
The pendulum disk is moved up or down by turning the adjustment nut.


1) Start by seeing exactly how far off the time is over a 24 hour period. Set the grandfather clock correctly by using your cell phone. Watch your cell phone time 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.

Grandfather clock pendulum adjustment

The Grandfather clock pendulum adjustment is done by turning the nut at the bottom up to speed up the grandfather clock or down to slow the grandfather clock.

2) Look at the clock again exactly 24 hours later and see if it is fast or slow. Move the nut up or down depending if it is slow or fast about a full turn for a minute a day.

3)  Look at the grandfather clock again another 24 hours later and see if it is fast or slow. Move the nut up or down depending if it is slow or fast about a 1/2 turn for a difference of about 30 seconds a day. reset the minute hand to the correct time as above.

4) Repeat the above using less turn on the nut until the pendulum is the correct length.

If your grandfather clock is slow or fast,  the speed is dictated by this adjustment. It is always easier for the clock to begin slow and then start raising the pendulum nut so the clock will gradually run faster until the correct time is achieved.




“I have moved my nut all the way down and the clock is still too fast”

The purpose of the adjustment nut is to move the pendulum bob ( the large disk) up or down.  Sometimes on older clocks the pendulum parts get tight or frozen and you might be moving the nut, but the pendulum bob stays frozen.

1) Take off the pendulum and place it backside up on a soft working surface.

2) Add a drop of clock oil (synthetic) on the threaded rod just above and below the nut.

3) Make sure the top of the nut is in the slot as shown.

4) Rotate the nut up and down the rod to evenly distribute the oil until the rotation feels smooth.

Make sure the “Bob” ( the disk) is moving up and down with the movement of the nut.  It is not unusual for the nut to move down, but the bob stuck above the nut. Good lubrication and making sure the top ridge of the nut is in the slot will correct this issue.

clock pendulum bob diagram

clock pendulum bob diagram
Click the image for an enlarged view



New grandfather clocks available from The Clock Depot at 30% Off and free shipping anywhere within the cont. United States.

Grandfather Clocks on Sale

Grandfather Clocks on Sale at The Clock Depot