Sherline, for example, specifies spindle nose runout of 0.0005 inch or less and spindle end play around 0.0002 inch or less, using two 20-mm ball bearings with adjustable preload. That’s only about 13 µm runout. A Chinese factory can absolutely manufacture that.
Manufacturers such as SIEG took conventional lathe architecture and mass-produced it.
There is nothing original going on there lots of copying
It's a pure manufacturing cost play to make something precise enough, rigid enough, and light enough[0] while being inexpensive enough for the market segment it's aimed at.
Is it a bummer that a US manufacturer went out of business trying to make money at that play? Yes. Is there anything nefarious going on with IP theft? Absolutely not.
[0] This is being sold to customers who don't hire riggers to move their machines.
And it's the one thing that unites every mainstream politician against Trump - they can't agree on tons of stuff, other than that we definitely should not be using tariffs to defend local manufacturers against Chinese (or any other) imports. I've been assured that those jobs are "not coming back." Well, big surprise - they're also not going to stop disappearing.
China merely followed the American approach towards industrial success.
It's certainly destructive to local companies, but that's what tariffs are for. If you think we should be making lathes, then throw tariffs on countries that make them cheaper. If that just moves the pressure to a consumer who still can't afford local lathes, stop handing free money to stockholders and real estate owners and start handing it to people who buy things.
There was a lot of knowledge transferred and training as part of that. For what its worth we previously had trained our North American partners. China could definitely not make our equipment themselves at that point in time. We did retain some key technologies but most of it was moved over.
I don't see how anyone can deny that the Chinese got a lot of the know-how as part of the mass transfer of production to China. 90% of their manufacturing know-how is from the west.
If the point is that Sherline specifically today doesn't have any IP they might care about- sure. It's been copied/reverse engineered/"stolen" a long time ago. I don't know when the Chinese entered the hobbyist machining market but when they did I'm sure copying existing designs wasn't exactly a barrier, or stealing trade secrets, or ignoring patents.