The conversion of a mechanical windup clock to battery operation is a practical way to restore a favourite clock to working order. Obviously, some mechanical clocks are worth having their movements repaired to maintain their value, but others that have no value outside of your appreciation of them can be converted to a battery-operated quartz movement. Once a few details are worked out, you will find that the conversion is not only inexpensive, it is a task you can perform in one hour or less with a new battery-operated movement and a few tools.
Check the size of the windup clock dial to determine if it can be fitted with a minimum battery movement size of 3 inches by 3 inches. Center the 3-by-3 measurement around the centre hole of the dial. Most windup clock cases have no trouble accommodating quartz movements because of the larger size of mechanical movements.
Remove the hands from the windup clock. Depending on the age of the clock, the hands may be held in place by a wedge pin or a retaining nut. Pull the pin out of the centre shaft using needle-nose pliers, or simply turn the nut counter-clockwise with one hand while holding the minute hand firm with the other.
Check the back of the clock case for access to the windup movement. If the clock has a pendulum attached to the movement, lift it up from the suspension hook and out from the case.
Check the upper and lower corners of the windup movement for brackets with screws used for securing the movement to the clock case. Remove each of the bracket screws, using the appropriate screwdriver, and pull the windup clock movement from the case.
Enlarge the centre hole of the clock dial to 3/8-inches by boring the hole out with a 3/8-drill bit and a drill. This size hole allows the threaded post of the battery movement to fit properly within the dial. Wear safety glasses when using the drill.
Clean all debris from the case after drilling and prior to installing the battery-operated movement.
Install the centre post of the battery-operated movement through the hole from the inside of the case. Place a brass washer over the post and attach the hexagon retaining nut. Hold the movement in the case using one hand and turn the hexagon nut clockwise with the other until snug.
Align the battery movement inside the case and hold firm. Tighten the hexagon nut with the adjustable wrench. Turn in a clockwise direction.
Install the minute hand onto its shaft. The hand base hole is slotted and must be aligned to fit over the slotted base of the minute shaft.
Place the ring nut onto the minute shaft to secure the minute hand if a sweep-second hand is to be used. The sweep hand can be installed by placing its centre tube over the shaft in the centre of the threaded post. If the sweep hand is not used, install the decorative crown nut to secure the minute hand.
Move the minute hand to the 12 o'clock position over the hour hand. Check the hands for clearance. The two hands must not touch each other as they rotate. If the sweep-second hand is used, check for clearance between it and the minute hand.
Install the manufacturer-recommended-size battery into the movement. Check the markings on the movement for correct polarity.
Set the hands to the correct time.
The battery-operated movement post length needed is determined by the dial thickness. The post is the brass threaded part that goes through the dial and is attached in the front of the dial by a hex nut. A 1/8-inch-thick dial requires a 3/16-inch post. A 1/4-inch-dial needs a 5/16-inch post. A 3/8-inch-dial needs a 7/16-inch post. A 1/2-inch-thick dial needs a 9/16-inch post. A 3/4-inch-thick dial requires a 15/16-inch post.
Wear safety glasses when drilling.