Well, you have to consider the reasons why you want to aim for a beat error of less than a particular value. Is it the ease of ability to “self-start”? Or is it the potential to increase overall balance amplitude. Or do you believe it will significantly improve timekeeping?
In my opinion, the reason why people are so interested in it these days is because it is now so simple to measure via timegraphers. Also the fact that the term has the word “error” in the title. And the fact that on modern watches it is so easy to adjust. You don’t hear people talk about it in the same way as positional-error which is usually far more difficult to adjust.
I will be attempting to build a fully functional, cased Elgin size 6s Grade 206 pocket watch.
This all began a short while ago, when I watched a video about getting in to watchmaking as a hobbyist in which the watchmaker being interviewed suggested starting with a scrap pocket watch movement, which can be found on the cheap on eBay.
I found the ubiquity and low cost of American movements to be counter-intuitive, as I would think 100+ year old watches would be quite valuable. This led me down the rabbit hole of the history of pocket watches, and America's former status as the worldwide leader in production volume of watches.
Flipping through eBay listings for non-running movements I ended up buying an Elgin one for about $20 shipped. Here is a photo of the movement-side, and here is a link to more info on Pocket Watch Database.
An interesting thing about this particular piece is the lack of a seconds sub-dial. None of the examples I see online on Pocket Watch Database share that, which is a bit weird to me.
Phase 1: Irresponsibly Hacking Away
When the movement first arrived, I decided to just take a stab at taking it apart. I figured, hey, it's a scrap movement that didn't cost me too much money, what's the worst that can happen? Well, I have to say I'm glad I learned the lesson of why NOT to do that, I just wish I'd been maybe a little more careful. As some fine folks here let me know, with a pocket watch or very old vintage movements, unless you're sure what you're dealing with isn't rare or valuable, don't treat it like trash.
I went at the movement with the smallest screw drivers I had available and started to take it apart. Here are the mistakes I made:
Not releasing the power from the mainspring: parts flew all over the place and I lost the center wheel for a couple weeks until recently I was looking for a fallen screw and came across it on the floor
Not taking pictures - there are a couple missing parts from the setting mechanism, so I am a bit unsure about exactly what was originally going on since I didn't do step by step photos (it's also hard to photograph step by step when the whole thing blows up )
Unscrewing the banking pins not knowing what banking pins are
During re-assembly, after trying to set the banking pins so the watch might run, I gave the balance wheel a spin with a toothpick with what I KNEW was too much force, and broke off the impulse jewel - this also is a lesson I knew in theory but learned in practice all too clearly, not to force ANYTHING, and also not to treat any part as if it's scrap or garbage
So with all that in mind, and with some insight from the community here which got me reading about the different Elgin models and parts, I've decided to source another identical movement, and a 6s-sized case + movement. Hopefully between the 3 I'll have enough good parts to have a fine working watch.
I'd also love to hear anyones thoughts about "switching," I intend to attempt to use all parts from the same grade and model movement. The case I'd be using would probably not have originally contained this movement, as I see lots of 6s pieces w/ case and movement for sale but not with this particular movement.
Note: since the horrific events described above, I've amassed a bunch of tools (most of them cheap versions from eBay) for watchmaking, including a screwdriver set, tweezers, movement holders, parts trays, cleaner with baskets and jars, hand levers, lubricants, Rodico, and probably some more stuff I'm not mentioning. Will be in a bit of a better position to attack this next challenge.
Anyway, stay tuned for Phase 2, when I will make what will hopefully a more measured and informed attempt at the build.