Things to check when repairing an antique American clock movement

July 25, 2007 | By | Reply More

Here are some things I check or do when repairing an antique American clock movement of the open spring type.

  • Check wear on time and strike mainwheel teeth and record on log sheet.
  • If mainspring arbor hooks have high backs, file down the backside to make it easier to unhook the inner end of the mainspring in the future.
  • Check ratchets and clicks – do any repairs necessary. File burrs off bottom of clicks. Tighten or replace click rivets if necessary. Make sure click springs are secure. Be wary of round brass wire click springs such as used in Sessions clocks. If you have any doubt about their reliability, replace with click springs made of round spring steel wire.
  • Check motion work and clean its pivots.
  • Chamfer ends of pin that holds center wheel hand set tension spring.
  • Check lantern pinions – make a list of those needing new wires or wires reversed. Check for loose holes in shrouds that might let the wires fall out.
  • Check pivot holes – make a list of ones to bush.
  • Check pivots – make a list of those to turn down and polish or just polish.
  • Check for “tunneled” pivot holes – where pivot is too short for the hole. Deepen oil sinks so pivot protrudes past oil sink. Seth Thomas #124 movements and many German movement have this problem.
  • Check pins: warning, lock, lift, etc for tightness.
  • Check pins in plates for tightness and smoothness.
  • Check for verge wear. Slight wear in a verge can be left alone, especially a deadbeat verge. If you decide to move the escape wheel to engage with an unworn verge surface, do it now, before pivot work.
  • Repair pinions first, then do pivot work, then bushing work.
  • Use a smoothing broach to polish any pivot holes not bushed. Polish large pivot holes with leather strip.
  • Test each wheel pair for proper depth and proper pivot hole fit by putting each wheel pair between the plates. With your fingers on each end of the driven wheel for pressure, turn the driving wheel and feel how smoothly it turns the driven wheel. If the wheel depth is way off, you can feel it in this way.
  • Assemble all wheels between the plates and tighten the pillar nuts and/or screws. Check sideshakes, endshakes and free rotation of wheels. Then install the verge and check and ajust the escapement.
  • Check suspension spring – if it is merely dimpled to prevent it from sliding through the suspension post, punch a small hole (use an old staking tool) and insert flat brass wire. (Use #22 soft brass wire, flatten it slightly, bend it partly, insert in hole, comlete the bend and hammer it slightly.)
  • Smooth and polish suspension rod where the crutch embraces it (take off enough metal to remove the worn spot).
  • Polish the pallets if necessary. Install verge, test and adjust escapement. Check crutch to make sure it fits tightly into the verge. Check and adjust crutch loop.
  • Clean pivots of strike lever arbors, smooth end of count hook, smooth lifting surfaces. Replace the leather in the strike hammer if it is hard or worn down close to the metal.
  • After assembly, push mainspring loop ends toward back plate so mainspring won’t rub on mainwheel.

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Category: American Clock Repair

Last updated: November 28, 2009

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