I am not a qualified clock repairer and the following information is how I clean clock movements.
This is only a guide for hobbyists who may wish to try it.
A mechanical clock movement should be serviced every five years by oiling the moving parts to stop wear and causing major repairs. First take out the movement from the clock case. This is usually achieved by removing clock hands, unscrewing mounting screws at the back or under the base board and lifting out the movement. Sometimes the face will still be mounted to the movement by pillars and tapered pins. Pull out the tapered pins to remove the face. Now that you have the movement on it's own, you may decide to clean it prior to oiling because of the dust and dirty condition it appears to be in and the black dried out grease in the bottom of the pinion gears.
Before going any further it is much safer when handling the movement to let down the spring tension on all the clock springs. DO NOT use just a clock key to do this as most times they get away under spring tension and usually take skin off your fingers. You will require a let down tool. I will suggest at the end of this write up a method of making one.
Apply the let down tool to the spring winder with your right hand and exert pressure to the wind spring, releasing the click with a small screw driver in your left hand and allow spring pressure to run down. Do this to all springs. If the clock has spring barrels see if you can remove them ( some barrels are made to be removed easily without parting the side plates ) otherwise leave them in position. If you have managed to remove the barrels scratch on the brass surface where they fit. I.E. T - for time C - for chime and S - for strike. If the springs are open springs as in Ansonia etc. just release their pressure.
Now the movement can be placed in a cleaning solution. I use petrol or kerosene. This is your choice, but the kero needs to be dried out with compressed air after cleaning. Petrol will evaporate itself. Use a small brush about 12mm wide and the bristles cut shorter to remove the dirt and grease from the pinion teeth and around the pivots. ( Pivots are each end of a revolving gear that passes throughthe brass plates. ) Try to tick the clock through its motion to free up hidden parts of the teeth and check that they are totally clean. You may have to use toothpicks to complete the cleaning process. Now you need to use clock oil ( DO NOT use inferior products as they will dry out in a short space of time and stop your clock ) Around each pivot on the outside of both side plates is a countersink which is called an oil well. You need to place a drop of oil in each one of these but not an excessive amount that will run down the side plate and pull out the lubrication. Also lubricate the winding spring shafts passing through the plates, click springs and ratchets for winding springs. DO NOT oil gears and pinions as these will collect dust in the bottom of the pinions and stop the gears from turning.
Also lubricate any moving shafts operating bells or chimes. Sometime these parts require grease as it will stay in place and not dry out over time.
The other point to oil is the rocker over the escape wheel. One drop of oil on the inside and outside of both ends of the rocker. This oil should then transfer to the teeth of the escape wheel when it turns. Springs should also be lubricated with spring grease. If they are in barrels, perhaps after 20 years of service they need to be removed, cleaned, greased and replaced. You would need special equipment to do this so it may be best to get a clock repairer to do this for you. If they are open springs, unwind them as much as possible in the movement, wipe excess dirt off, maybe rub down with fine wet and dry paper to make them smooth and rub on both sides with a good spring grease. Wind them back into the movement as you go. Try to mount movement in a temporary test bed, wind up springs several turns and check out the running of the clock before installing it back into the case.
LET DOWN TOOL
A let down tool is a special tool purchased to do a special task. To make a simple tool cut a piece of broom handle to approximately 120mm. long. Drill into one end a round hole equal to the diameter of your clock key and around 30mm deep. Next cut a slot across this hole so the wings of the key will push into it and it is reasonably tight. Round over the top end of dowel and sand all of it smooth to prevent splinters. The idea is that when the click spring is released the dowel can slip through your hand slowly until the spring tension is released.
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