5 ms·

Aye. I have a pretty cheapo mill, 2k for the mill and 6k all in (most expensive sector is metrology)* Can easily work to under 0.01mm which is absurdly small w

Aye. I have a pretty cheapo mill, 2k for the mill and 6k all in (most expensive sector is metrology)* Can easily work to under 0.01mm which is absurdly small when you're faced with it. Then you see the guys working under 0.0002/1 and... it's just incredible. > gets as close as any human endeavor to actual perfection Truly. The only thing that matches it in terms of the physical is Xnm chip production and atomic level physics research. But those are far less hands on, and require tens of millions in equipment (plus the parts areade by machinists anyway). * can provide running costs breakdown if interested

rfrey 5y ago
> (most expensive sector is metrology) Absolutely. But ohhhh... those instruments. I saw a friend with an electronic gauge put it on one end of a 1' bar of steel. He put the gauge on one end and zeroed it. Then he breathed on the other end. We watched the needle cliiiiiiiimmmmbbb.... then fall back to zero over 3 minutes or so.
- tomcam 5y ago
  Holy crap. Is this because the steel expanded an infinitesimal but somehow still measurable amount?
  - theelous3 5y ago
    Yes. There's a joke in machine shops working to insane tolerances. "just breathe on it till it measures in spec" There's a great video by oxtoolco on youtube where he's seeing which is "thicker". A sharpie mark or some machinists blue. Measuring in the millionths of an inch.
    - rfrey 5y ago
      Spoiler: a sharpie mark is about one ten-thousandth of an inch thick (depending on color, because size of the pigments!) An interesting use of this bit of trivia: when machinists are trying to grind a block square, they may measure a slight deviation from 90 degrees - i.e. they see that each of the two opposite faces are parallel, but the angle they make is out of square. They have a parallelogram. If you draw it, you can see that if they put it back on the grinder, and shim one edge of the face contacting the table, when they grind the opposite-to-the-table face they can bring it closer to square because they'll be grinding a wedge off the top face. They use a quick swipe of a sharpie marker as a shim.
  - rfrey 5y ago
    Yes exactly. I was blown away (ahem) and instantly regretted my life choices, which until that point had not involved microns in any way shape or form. The instrument readout looks like this: https://www.perfectionmachinery.com/assets/item/hires/40961_7.jpg https://www.perfectionmachinery.com/assets/item/hires/40961_... except his had adjustable ranges. Every tick on that needle is one millionth of an inch - by comparison a red blood cell is about 40 millionths and the smallest bacteria is about 5 millionths long. This instrument has a read head connected with a cable, that has a finger on it that rests on the part under test. Under normal use you'd slide the part around under the finger to look for variations in thickness - obviously that requires and extremely flat surface to slide around on.

rfrey 5y ago

> (most expensive sector is metrology) Absolutely. But ohhhh... those instruments. I saw a friend with an electronic gauge put it on one end of a 1' bar of steel. He put the gauge on one end and zeroed it. Then he breathed on the other end. We watched the needle cliiiiiiiimmmmbbb.... then fall back to zero over 3 minutes or so.

tomcam 5y ago
Holy crap. Is this because the steel expanded an infinitesimal but somehow still measurable amount?
- theelous3 5y ago
  Yes. There's a joke in machine shops working to insane tolerances. "just breathe on it till it measures in spec" There's a great video by oxtoolco on youtube where he's seeing which is "thicker". A sharpie mark or some machinists blue. Measuring in the millionths of an inch.
  - rfrey 5y ago
    Spoiler: a sharpie mark is about one ten-thousandth of an inch thick (depending on color, because size of the pigments!) An interesting use of this bit of trivia: when machinists are trying to grind a block square, they may measure a slight deviation from 90 degrees - i.e. they see that each of the two opposite faces are parallel, but the angle they make is out of square. They have a parallelogram. If you draw it, you can see that if they put it back on the grinder, and shim one edge of the face contacting the table, when they grind the opposite-to-the-table face they can bring it closer to square because they'll be grinding a wedge off the top face. They use a quick swipe of a sharpie marker as a shim.
- rfrey 5y ago
  Yes exactly. I was blown away (ahem) and instantly regretted my life choices, which until that point had not involved microns in any way shape or form. The instrument readout looks like this: https://www.perfectionmachinery.com/assets/item/hires/40961_7.jpg https://www.perfectionmachinery.com/assets/item/hires/40961_... except his had adjustable ranges. Every tick on that needle is one millionth of an inch - by comparison a red blood cell is about 40 millionths and the smallest bacteria is about 5 millionths long. This instrument has a read head connected with a cable, that has a finger on it that rests on the part under test. Under normal use you'd slide the part around under the finger to look for variations in thickness - obviously that requires and extremely flat surface to slide around on.