[formerly_proven]

There's a "high tech" (i.e. they mostly don't use cutting tools) machining shop nearby; their proprietary machines (designed & built in-house, never sold or leased externally, only used for contract manufacturing) are repeatable within a few µm (they offer tolerancing below 5 µm on finished parts) and move about as quick as the rapid traverse on a more standard CNC milling machine.

[SAI_Peregrinus]

Nanotech Systems (Moore's current name) make a high-precision drum lathe with 1nm positioning precision, with a 2600mm working area [1].

1 part in 2,600,000,000.

Dan Gelbart built his own lathe with <1µm final part tolerance [2].

Within a few thousandths of an inch isn't very impressive. I can hold 1 thou on a cheap manual lathe (Grizzly G0602 10"x22" working area), with a decent amount of care. Holding to tenths (1/10000") is impossible with the equipment I can afford though.

[1] https://nanotechsys.com/wp-content/uploads/2019/12/HDL2600-B... [2] https://www.youtube.com/watch?v=sFrVdoOhu1Q

[formerly_proven]

That's resolution, not precision or repeatability, although such high resolution is very impressive. I'm not sure how exactly a glass scale is supposed to work to 34 pm, I assume these use analog interpolation between marks or perhaps some kind of interference mechanism.

[wjdoge]

EDM?

[formerly_proven]

Laser