How Did Watchmakers Make Precision Gears?

[ralph124c]

The first pocket watches were made by a Peter Heinlein, of Nuremburg, Germany, in the 1500’s. They were called “Nuremburg Eggs”, and they were about the size of a large egg. My question: how did these early watchmakers make the precision gear wheels, long before the invention of the precision lathe (ca 1750)? Were these early watches at all accurate? I have a few antique pocket watches (from the 1880’s)and the workmanship in them is absolutely amazing! But I can’t imagine how difficult it must have been to make tiny gears back 500 years ago-were they manually filed down tofit?

[yabob]

One take on it:

Here, then, is something which we can really consider a watch. Let us see how it compares with those that we know to-day. In the first place, being egg-shaped, it was thick and heavy–you would not like to carry it in your pocket. It had no crystal and only one hand–the hour-hand. So much for the outside.

Inside, the difference was still greater. The works were made of iron and put together with pins and rivets. It was all hand-work–expert workmanship, indeed–but look at the works of your own watch and try to imagine cutting the teeth in those tiny gears, or making those delicate springs with files and hammers. As pieces of hand-workmanship, therefore, the watches made by Henlein and his followers were remarkable; but when compared with our modern watches, they were crude and clumsy affairs.

Furthermore, they were poor timekeepers. They had the old foliot balance running parallel to the dial. This was all very well as long as the watch lay on the table with the balance swinging horizontally. But as soon as it was carried, in a perpendicular position, the arms of the balance had to swing up and down, which was quite another matter. And then, of course, the crudeness of the works produced a great deal of friction. This made it necessary to use a very stiff mainspring, otherwise the watch would not run at all. Such a spring exercised more pressure when fully wound than when it was nearly run down. And so the worst fault of the foliot was that it speeded up under increased pressure.

From http://www.love-watches.com/Invention-Watch.htm

Minute hands didn’t appear commonly until 1700 or so (that article mentions their occasional use a century before then). Very probably, that was about when watchmakers started producing mechanisms that were reliable enough to make a minute reading worthwile.