Assess how fast or slow your clock is running. Do this by winding the clock, setting the time and starting the pendulum with a gentle swing.
Wait a full day, then see how far off it is, and in which direction. If it's more than a minute off, the pendulum should be adjusted.
Find the adjustment nut at the bottom of the pendulum. This raises and lowers the pendulum, which in turn speeds or slows the rate of the clock. The shorter the pendulum, the faster the clock will run.
If your clock is running too slow, turn the nut clockwise by one full turn, to raise the pendulum. If it's running too fast, turn it counter-clockwise. Wind and reset the clock as before, then wait one full day.
Check the clock's time again. If it's still off, adjust the nut farther. Repeat over days until the clock is keeping the correct time.
Things You Will Need
- A watch or other consistent time source to measure against the grandfather clock.
- Clocks vary in terms of how much the turning of the adjustment nut changes the time. When you adjust it the first time and check the time a day later, take note of how much impact it has had (i.e., if one turn of the nut slows or speeds it by one minute, or two, or less). Use that information to help determine how much to turn it the second time.