Over time, mainsprings (winding springs) weaken, become brittle, crack, or break. Barrels (the cylindrical containers that contain the mainsprings on some clocks) wear out. Pivots (the "tips" of the arbors on which the wheels [gears] are mounted, and which run in the clock's front and rear bearings) become scored and become thinner. Front and rear bearings wear out. Wheel teeth (gear teeth) and lantern wires (a type of gear inside the clock) become bent or broken, or lose material from their surfaces. Ratchets (the special gears that retain the pressure of the mainsprings during and after winding) become worn down, deformed, or damaged. Ratchet pawls, or "clicks", become worn out and loose (the ratchets' and the clicks' good condition and proper action, is vital for the tension of the mainspring to be retained safely and properly).
The above conditions constitute normal wear and tear for an old clock.
The following describes a repair/rebuilding of a clock mechanism by JFK:
- Clock mechanism, or movement, is removed from the case and completely disassembled, part-by-part, right down to the wheels, springs, nuts, screws and washers.
- Each part is washed and dried completely, in order to remove dirt, dust, grime, old oil, and metal shavings. WD-40 and other "spray" lubricants, kerosene residue, and all the other contaminants that are on the clock movement and its parts, are also removed during this process.
- When cleaned and dried, each component is examined for wear and tear, poor quality prior "repairs", existing problems, and potential problems. Prior poor-quality repairs are "un-done". For example, electrical solder or "epoxy" or "superglue" that were used in prior repairs is removed from the clock parts. This is common!
- Ratchets are replaced with lathe-turned, custom-machined replacements, if required. Ratchet pawls, or "clicks", are replaced and re-riveted, if required, as well.
- Pivots (axle tips) on the ends of the wheel (gear) arbors are replaced if required, and/or polished to a mirror finish in an Austrian-made pivot polishing machine.
- New bronze bearings (bushings) are installed throughout the clock, using either a German or American made bushing machine.
- Mainwheel bearings are replaced, if required. Mainwheel bearings are the large bearings for the clock's winding wheels. Front and rear mainwheel bearings are too large to use the standard bushings that the bushing machine installs, so replacements are custom-machined of bronze in the lathe, and installed in the clock.
- Barrels, if the clock has them for containing the mainsprings, are rebuilt in the lathe. The barrel gear is gripped in the lathe, bored out, and receives a new lathe-turned bushing, custom machined and fitted; a new brass barrel cap is custom machined and fitted to the other end of the barrel.
These machining operations to the barrel eliminate decades of wear and tear on the barrel; they bring the barrel back up to factory original specifications (or better); they prevent power loss from friction; they prevent poor running of the clock from lack of available power; and they also ensure that the barrel will not wear out again for many years. And if any teeth on the barrel are bent or broken, either a new barrel gear is machined and fitted to the barrel, or, an entire new barrel is custom-made.
- Damaged wheels (gears) and pinions, if any, are replaced with custom-made replacements.
- The clock's components are cleaned and dried again to remove oil, polishing grit, and other shop contaminants.
- The clock is reassembled and oiled, and the escapement (the part of the clock mechanism that causes the pendulum to oscillate or "tick" back and forth) is adjusted to function properly. If it does not, it is repaired or rebuilt. The clock is then tested in-shop for proper running, good performance, and of course, timekeeping adjustments.
- After testing on the bench, the clock is disassembled again; all its components are washed and dried a final time, and the clock is then reassembled, oiled, and placed in the case, and tested in the case for a week or more.
All of the above ensures that all problems are addressed and remedied, and ensures many years of trouble-free, proper operation of your clock.