A Seth Thomas mantel clock is a marvelous example of the clockmaker's craft. Each clock is a thing of beauty that enhances any room in which it is placed. Seth Thomas mantel clocks are constructed to the highest standards and as such they cannot be over wound (a common concern). However, that being said, each cock must be wound on a regular basis and each clock must be wound carefully in order to keep it running accurately for years to come.
Determine if your Seth Thomas mantel clock is a 7-day clock or an 8-day clock. On most models it will say right on the face of the clock which type it is. Seven-day clocks must be wound every 7 days, and 8-day clocks must be wound every 8 days. If you are unsure you should wind your clock every seven days.
Look on the back of the clock. You will see three large holes (just large enough for the clock winding key to fit into) plus one or two smaller holes (often just large enough for the small end of the key to fit into). The two smaller holes are for speeding up or slowing down the clock and for turning the chimes off and on. The three larger holes are the ones we are interested in--they are the ones we will need to wind every 7 or 8 days. On some models the three winding holes are on the front of the clock. Winding instructions are the same, regardless of where the winding holes are located.
Push the large end of your clock winding key gently into the hole on the right as you look at the back of the clock. This hole allows you to wind the 15-minute chimes. Gently turn the key clockwise. Keep turning it until you feel resistance and the key stops turning. Remove the key.
Insert the large end of your key gently into the center hole. This hole allow you to wind the main clock mechanism, which allows the clock to run and to keep time. Turn the key clockwise firmly but gently until you feel resistance. When the key no longer wants to turn simply remove it.
Insert the large end of the key into the hole on the left. This winds the hour chimes. Turn the key clockwise firmly but gently until you meet with resistance. When the key no longer turns easily remove it and place your clock back on your mantel. Your clock is now set to run for 7 or 8 days, depending on the model you own.