Watch Repair
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Antique Watch repair • Wrist watch repair • Pocket watch repair
Your Watch Repair
Troubleshooting Guide
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Watch Mechanism Theory |
Welcome
Motive Power
Motion Works
Escapement
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Lever Escapement |
Balance Wheel
Balance Assembly
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Watch Repair Trouble Shooting |
Introduction
Mainspring Problems
Over Wound Watch
Positional Error
Barrel Problems
Catching Mainspring
A spring driven watch derives all of its power from the mainspring. The mainspring must be in good condition with no burrs, rust or kinks and must be clean and properly lubricated if it is expected to deliver its full power to the works. The coils must be able to slide freely with no obstruction as it slowly unwinds. If its surface has any burrs or scratches it may catch or bind in places causing uneven power transfer to the train. If the coils cannot slide smoothly along the surfaces of one another they will tend to stick together for awhile until finally slipping. The sticking together of the coils causes uneven power distribution and will reveal itself in fluctuating tick amplitude. If you notice that the watch has a soft tick and then becomes noticeably louder then soft again and does not follow any predictable pattern then there is a good chance the mainspring needs some attention. The arc or motion of the balance wheel may also vary if the spring sticks together for long periods of time and then suddenly slips. Of course there are other situations that can cause similar symptoms such as bent pivots or bent wheel teeth but these symptoms will usually repeat themselves in a regular pattern. When winding a mainspring for the first time after it has been cleaned and greased it’s very important to wind it fully, let it back down and then wind it fully again. If using a mainspring winder do this in the winder several times and then inspect the spring to see that the grease has spread evenly over the entire spring. This includes the most inner coils where most of the pressure is exerted.
This helps to distribute the grease evenly along the springs width and length. Failing to do this will often cause uneven power distribution throughout the duration of the first few windings. This is made quite obvious when timing out a clock with a platform escapement and with watches. When you hear a tick that sounds exactly like a “galloping” horse it’s usually caused by an uneven distribution of grease. What’s actually happening is the effective length of the spring is constantly changing due to sticking and slipping. When one coil sticks to another coil the effective length of the spring is made shorter which increases the strength or power that the spring delivers to the escapement (see diagram following page) which to put simply causes the balance wheel to swing so far that it bounces off things that it should not. This bouncing adds an extra “tick” to the normal ticking which really does sound like galloping. The result is more balance wheel motion while the coils are stuck together dropping back down to normal motion when the coils assume their normal position. This makes it almost impossible to correctly time out any watch or clock during its first winding. So... after applying grease remember to fully wind, unwind then wind again. Actually, doing this several times will help to insure that the entire spring has been properly lubricated. Also, if a spring is defective and destined to break it will usually happen within the first few windings. Far better to have it break in the mainspring winder than in the watch.
The power of a mainspring is determined by its thickness, width and length. If the thickness and width remain the same for a given spring but the length is cut in half the spring will be twice as strong delivering twice the power to the wheel train. The strength of a spring changes in inverse proportion as its length changes. So if a springs length is reduced by 10% its strength will also be increased by 10%. This shortening of a spring is exactly what takes place when two or more coils stick together. The springs effective length no longer begins at the barrel arbor hook but now originates at the sticking point and terminates at the barrel hook. Hence, we have a shorter, stronger spring delivering excess power until the coils finally slip back into place.
Doesn’t make sense? Try it for yourself. Hold a spring at point D and A and wiggle it around. Now let go of point A and grab it around point B. You should notice it becoming a bit stronger. Actually at this point its probably around double the strength. Now release point B and hold it at point C and D. Move it now and you’ll have no problem detecting the difference in tension.
Improper mainspring replacement is something you will encounter periodically in both watch and clock repair. Often a watchmaker does not possess or cannot locate an exact replacement spring for an older timepiece, substituting the original spring for one with the nearest dimensions possible. If certain precautions are not considered this may result in difficult to diagnose problems. If a mainspring is chosen that is too wide it will press against the bottom and cap of the barrel which will result in jamming the mainspring and obstruct the smooth slipping motion necessary for a spring to function correctly. If the barrel cap is not seated flat in its barrel seat then as mentioned earlier too wide a spring is suspect. Again, tolerances are so close in watches and clocks that you will often see scratch or wear marks scraped on the outside of a protruding cap by a close running center wheel, center wheel bridge, barrel bridge or plate. It’s necessary to mention here that these same symptoms can occur from a spring that has been incorrectly wound into a barrel by hand rather than with a mainspring winder. If not done properly it can distort the spring into a conical shape. You can check this by laying the spring on a flat surface. If it doesn’t lay flat but instead assumes a cone shape then when installed in the barrel it will exert some pressure on the bottom and cap of the barrel dissipating some of its energy in the wrong direction.
E-Mail: Lance Young
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