1. How to adjust your grandfather clock pendulum bob: The round brass disc on the bottom of your pendulum rod is called the pendulum bob. The nut located on the bottom of the bob is used to adjust your grandfather clocks time keeping ability. If the bob is raised up, your grandfather clock will run faster, if lowered, your grandfather clock will run slower. You can remember this principle, with the phrase A SHORT DOGS TAIL WAGS FASTER! Expect an accuracy of at least 1 minute, fast or slow per week. Start by setting your grandfather clocks time to an accurate electric or quartz clock or watch. Check the time 24 hours later. If the clock runs fast, turn the nut to the left (as you face the clock) and the bob will be lowered, slowing the clock. If the clock runs slow, turn the nut to the right, which will push the bob up, speeding up the clock.Then reset your grandfather clock to the correct time again. Keep a written record of the distance you turn the nut each day and the resulting minutes off. Do this every day until you have zeroed in within 1 minute of the correct time. Then, switch to checking your grandfather clock every 7 days, using the same process until your grandfather clock keeps time within 1 minute per week. Grandfather clock repair secret: Many grandfather clocks are designed so that one full turn of the pendulum nut equals 1 minute per day. So, for example, if your grandfather clock is 2 minutes fast in a 24 hour period, turn the pendulum nut 2 full turns to the left. Keep in mind that this rule of thumb is not true with all grandfather clocks. And remember, mechanical clocks are not as accurate as modern day electric or quartz clocks! When you regulate the pendulum of your grandfather clock, you are attempting to achieve the best timekeeping possible from a mechanical clock between weekly windings. During your weekly grandfather clock weight windings, its a good idea to make it a practice to also reset the minute hand to the exact time of day as established by a quartz clock in the house.
2. Does your grandfather clock have two nuts attached to the pendulum rod? Some grandfather clocks have not one but two nuts on the bottom of the pendulum rod. If your grandfather clock has two nuts, then you probably have a real accurate grandfather clock! Many owners believe that the bottom nut is used as a “lock” nut against the the top nut. Not so! Grandfather clock repair secret: Make sure the bottom nut doesn’t touch the top nut. Let the top nut raise or lower the pendulum bob until the most accurate timekeeping has been obtained. Then, by turning left or right, use the weight of this nut as the final delicate time adjustment to regulate your grandfather clock.