I see vintage watches repaired. When the case is opened the movements are so well-designed and engineered, with gear teeth cut to the 0.1 MM level and thin, perfect jewels. How is such mechanical precision possible from decades ago?
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Well, today we produce nanometer technology (watch some youtube videos about CPUs, wafers and such and you will get an idea of this). So it is not too astounding that we produced 0.1mm precision gears and such decades ago.
I think you underestimate just how good humans are at measuring and making things.
Thr biggest issue is time and skill….we like to move fast but precision takes time
Many great ancient buildings are built within inches of perfection
Thy pyramid of Giza is oriented n/s/e/w and is only off by 1/15 of 1 degree accurate……there are lots of ancient monuments where the walls are near perfect vertical
Don’t underestimate the precision of a very well trained, likely lifetime apprenticed had with a file.
Even before machine tools we were capable of training incredible precision. It just takes stupid dedication, or failing that, an indenture.
If you want to look at groundbreaking precision, look to the development of marine chronometers. Unbelievable given the resources at hand, yet they made them
You’re using the word “tolerance” in a way that implies you don’t know what it really means.
Really old watches didn’t have the parts made to a tolerance, they had each part made to fit that specific watch.
A production tolerance is a fairly modern concept, where you design a product such that all parts within a certain tolerance will fit and function. So the blueprint will call out toleranced dimensions, say 2mm +0 -0.05 would mean anything from 1.95 to 2.00mm is within tolerance. A pin or axle shaft made to that tolerance will fit more or less tightly in a hole toleranced as 2mm +0.05 -0, meaning a hole anywhere from 2.00 to 2.05mm is in tolerance. You design all the parts and their tolerances such that any combination of variations within the tolerance of each part will still make a functional product.
Old timey manufacturing wasn’t based on this same system of tolerances and interchangeable parts. Instead you had more approximate dimensioning, with some parts dimensioned in the blueprint and others made “to fit”. So the watchmaker would have a set of ground jewel bearings, for instance, and those would be whatever dimensions the jewel polisher had made them. Some variation to be expected. He would then make the mating axles to fit the jewels, not to fit a dimension on a blueprint. Simply polish down the axles slowly and test fit along the way, until the fit is perfect. All other mating surfaces are fit similarly- you make parts the right shape and slightly oversize, then carefully polish them down until they fit together just right.
Handmade mechanisms made to fit like that can have even closer fit of parts than most modern production, because you don’t have to allow for slack caused by stacking tolerances (if all parts end up towards the minimum or maximum tolerance you could get either a very loose or tight fit in total). The downside is it’s very labour intensive, and you cannot simply swap in a new part to repair something because parts form one handmade mechanism won’t fit a seemingly identical watch without hand fitting.
What everyone else has said, but don’t forget about survivorship bias. The only watches still around are the best made. All the crappy watches broke a long time ago.
Yeah, you’re just underestimating how good we are at making stuff. I was able to get those tolerances in a few months on a lathe from the 50s as a complete novice. We don’t do it by hand, we have setups to hold stuff in place and move stuff very smoothly and precisely and nothing is eyeballed. And we can use those tools to make even better tools. It’s a feedback loop.
Also, watch movements are made to be tuned after they’re made. So if it’s off a bit, you can adjust it.
[https://en.wikipedia.org/wiki/Antikythera_mechanism](https://en.wikipedia.org/wiki/Antikythera_mechanism)
First Century BC
Check out the YouTube channel “Click Spring” – he does a lot of research and reproduces the techniques used in ancient times to get incredible levels of precision with simple tools and supplies.
A mega meter is a pretty big tolerance. Or did you mean “mm”?
We’ve had Vernier calipers for almost 400 years and working micrometers for well over 150. Measuring to 100 micron precision isn’t particularly new. For context, that’s a pretty standard normal-tight tolerance in modern machining. If needed, I can specify an order of magnitude tighter without too much guff from my machinist.
What has changed is how manual and iterative the process is to achieve that level of precision. We’ve replaced hours of skilled labor with seconds of automated machining.
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