Mainspring Repair/Replacement
Example of a Mainspring That Has Taken a Set (Left)
This photo illustrates what often happens when a mainspring ages. The old mainspring on the left is the same length as the new mainspring on the right. The left mainspring has taken a "set" meaning that it has lost some of it's springiness. The old coil has 4 extra turns of the spring permanently set. This means that it has lost four turns of strength and may not keep the clock running for a full week.
Mainsprings are hard workers. They store a great deal of energy. Unfortunately, they don't last forever. If they don't fail by breaking, they can loose their effectiveness by taking a "set" (see photo). If a mainspring is noted to be failing during overhaul, replacement springs are available for most clocks. If a mainspring breaks while the clock is in service, the explosive release of energy can often damage other parts of the geartrain. Sometimes, a spring will fail at it's its end connection. If the rest of the spring is still good, the broken end can be removed and a new attachment point (hole or loop) can be fashioned. It's good practice however to simply replace a failed mainspring if it is still commercially available.