Two commonly heard phrases in the clock business are “I think I wound it too tight” and “It’s overwound.”
Certain sellers on a popular auction site, who I notice sell hundreds of clocks in “unknown” condition, love the term overwound. You may have noticed they also somehow “Don’t know much about clocks and don’t have a key to fit so can’t test this clock.” Sure, and the clock was only run on Sundays by a little old lady who had it serviced every three months… The vast majority of American spring wound clocks use a number 6 key. I buy them by the dozen. Anyone who handles clocks has them all over the place. This is the less than honest use of the word “overwound”. It sounds so much less expensive to sort out something overwound than an honest “This clock is filthy dirty and worn to boot. If you love working on clocks this one is for you!”
Perfectly honest people use the term too. Probably because clocks stop working at some point, people wind the clock, and it still doesn’t run. So they blame themselves, recall hearing others use the term, and assume they broke their clock. Relax, the clock was broken already, it just happens that when weak parts fail or worn parts jam it’s when the most force is applied. The clock may not have needed winding in the first place, but that’s usually a good first thing to try.
Unless you have applied just a silly amount of force to the winding key, you didn’t wind your clock too tightly. If you wound it until you couldn’t wind any more, then grabbed a big wrench and really cranked until you heard a big bang, you overwound it. It’s darn near impossible to wind so hard using just your fingers that you harm the clock.
In the case of spring wound clocks, the old oil or spring grease gets hard and sticky eventually. When you wind the clock completely this sticky, sometimes almost tar like layer of old lubricant glues the coils of the spring(s) together. Sometimes when the clock gets warm or sits for a period, the owner will report hearing a bang or a bump, and the clock starts to run again.
In other cases, the clock may be worn. When you wind the clock fully, worn pivots and holes combine to jam the works. Usually the clock will run poorly or may only run for a few days between windings.
When a clock is this dirty and worn, it’s time for a complete restoration or overhaul of the movement. Adding oil to a dirty clock may make it run a bit, but all that dirt and hardened oil is just making an abrasive slurry that does yet more damage.
I hope some folks find this useful,