9 ms·

The only person here that knows what they're talking about. Everyone's talking about calipers :/

bamboozled 6y ago
I love that out of all the more complex ideas about what may have been used, it turns out likely to be a solid piece of metal with of a given thickness, couldn't get more simple than that.
- WrtCdEvrydy 6y ago
  If you're into 3D Printing, feeler gauges are also a great way to level your bed... move the extruder 0.04 above the bed at four points, stick your 0.04 feeler under it and adjust the springs until it touches the feeler. Voila, one perfectly leveled 3D printer bed.
  - jrockway 6y ago
    Most people use a sheet of paper for this. I wouldn't use it to check the tolerances of an airplane part, but it gets you 99% of the way there.
    - WrtCdEvrydy 6y ago
      I like the sheet of paper method, but I have gotten a lot more use out of a $0.15 feeler gauge and I get consistently better prints... but I don't have the tools to scientifically quantify it so it could be placebo.
  - serf 6y ago
    that's a weird in-between two more popular ways of doing it. The non-precise way you've already heard about, sheet of paper, check for dragging. The better (more precise) way, is using a magnetic base micrometer attached to your extruder head. You can then watch the bed run-out in real time; if your 3d printer supports many configurable sections across the bed ( I know Prusa style cartesian units mostly all support quadrants) you can record the run out everywhere across the plane without any more physical work than watching the gauge and recording the results. P.S. be careful using both the micrometer and the feeler gauges on a 3d printer bed. Most work plates now-a-days are using PEI coatings that'll scrape off easily with metal-on-metal contact.
    - WrtCdEvrydy 6y ago
      > using PEI coatings that'll scrape off easily with metal-on-metal contact. Yeah, you're correct, it's a glass bed so I use it to do the 4 corners (every few months) and then use a BL touch to do a 3x3 grid on top of it.
- bilbo0s 6y ago
  couldn't get more simple than that. Believe it or not, that's actually a lot of the idea that drives commercial aviation design. Or used to anyway.
  - KMag 6y ago
    ... and most engineering in general. Simple solutions tend to be very robust and often cost-effective.
    - noir_lord 6y ago
      and easier to troubleshoot/replace. > A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over, beginning with a working simple system. - John Gall
- na85 6y ago
  That's what real engineering is about: the simplest tool or process that will get the job done. Despite what we see on the web more and more, this principle applies to code too. It shouldn't be about stacking up layers of complexity for no good reason.
  - Gibbon1 6y ago
    Somehow your comment reminds me of a pissing match I saw between a young aerospace engineer and an old retired one. The old guy was right in his argument that it doesn't matter what the constraints on materials and dimensions are, it that they come from somewhere and are documented. His example was designing brackets for a Indonesian construction company that was using locally sourced tropical softwoods for constructing buildings. The brackets were designed to be made with 'steel' and the tolerances were compatible with a hungover guy running a drill press.
- cartoonfoxes 6y ago
  They're deceptively simple. If you want to get into the history of modern manufacturing, a lot can be written about the development of gauges of accurately known dimensions.
  - nitrogen 6y ago
    I went down a rabbit hole of videos last yearish about the origins of precision (that should be a searchable phrase to get started).
    - cartoonfoxes 6y ago
      Go find a PDF of "Fundamentals of Mechanical Accuracy" by Wayne R. Moore, if you haven't already seen it. That book, along with George Daniels text "Watchmaking" are some of the top inspiring works on the mechanical arts in my collection.
  - noir_lord 6y ago
    Somewhat sadly a lot of the drive for that tolerance was weapons, until we could accurately make very high tolerance (for the day) parts you couldn't use parts from one rifle on another without a smith, it certainly wasn't field serviceable - this imposed a lot of maintenance overhead until they solved it properly. It seems like we really like to push the limits when it comes to shooting each other.
    - linuxftw 6y ago
      > Somewhat sadly Weapons can be used for defensive purposes. There's nothing inherently wrong with them, only how people use them. > parts you couldn't use parts from one rifle on another without a smith You cannot swap bolts in the field on most rifles. At minimum, you require a go/no go gauge. The tolerances on modern firearms are very precise.
      - int_19h 6y ago
        That the tolerances are so precise is exactly why you can do that on most modern rifles. It depends on the design - specifically, how they achieve headspace. On an AR-15, or almost any firearm with a similar bolt locking arrangement, bolts - indeed, entire BCGs - are swappable in practice, and people do that routinely without bothering with gauges regardless of what the manual says. On AK and similar designs, yeah, that's a really bad idea.
bewaretheirs 6y ago
Yep. To check tolerances, you'd need a go/no-go pair -- one that should fit, and a slightly bigger one which shouldn't.
- lisper 6y ago
  This is a thing that non-aviators often don't realize about aviation in general: the hard part is designing the artifacts and processes so that by the time you get around to operations, everything is routine and nothing is hard. Flying, building and maintaining airplanes seems hard, but that's mainly because of the volume of stuff you need to know, not because any single item is particularly difficult. All aircraft are built, maintained, and flown by mere mortals. (The designers, on the other hand... ;-)
  - int_19h 6y ago
    It's not just aviation. Our entire industrial civilization works like that, and this is the only reason why it can work. We are surrounded by high-precision machinery even in daily life, and are completely oblivious to just how much technomagic it is - and how much historical effort went into building the industry up to the point where it can produce such things so easily and cheaply.
nabilhat 6y ago
Who even uses calipers for critical precision? Calipers are for dimensions machinists append with -ish, as in four thousandths-ish. Important dimensions deserve a micrometer, especially the feeler guage that just said you need to tell your boss to scrap a 737. Decent machine shops even have different classes of micrometer; there's the one you carry in your pocket, and then there's the fancy set locked up in your boss's office that only comes out for special occasions, like when your boss has to tell their boss to scrap a 737.
- cartoonfoxes 6y ago
  I see this in my own shop. Digital displays instill people with greater confidence in the measurement than is warranted. This is something of a UI fail, as the tool manufacturer (Mitutoyo) has very clearly defined measurement precision for all their metrology equipment (+- 0.001" and 0.0015" for the calipers).
  - sgnelson 6y ago
    That is a very interesting observation, thank you. I've never thought about the digital vs analog in terms of actual "oh, it's digital, it's better." measurement variation. In my experience, I think you're probably right, it does seem like people may take them as "more accurate."
- kayfox 6y ago
  You don't scrap a 737 for some worn out parts.
  - teh_klev 6y ago
    Not that I want to be pedantic, but that's a rather sweeping statement. The decision to scrap would depend on things like the number of flight hours and takeoff/landing cycles on the air frame and the number of other worn parts, hitting meantime-before-failure on large numbers of parts/assemblies, such that it may be more economical to scrap.
  - doodlebugging 6y ago

I love that out of all the more complex ideas about what may have been used, it turns out likely to be a solid piece of metal with of a given thickness, couldn't get more simple than that.

WrtCdEvrydy 6y ago
If you're into 3D Printing, feeler gauges are also a great way to level your bed... move the extruder 0.04 above the bed at four points, stick your 0.04 feeler under it and adjust the springs until it touches the feeler. Voila, one perfectly leveled 3D printer bed.
- jrockway 6y ago
  Most people use a sheet of paper for this. I wouldn't use it to check the tolerances of an airplane part, but it gets you 99% of the way there.
  - WrtCdEvrydy 6y ago
    I like the sheet of paper method, but I have gotten a lot more use out of a $0.15 feeler gauge and I get consistently better prints... but I don't have the tools to scientifically quantify it so it could be placebo.
- serf 6y ago
  that's a weird in-between two more popular ways of doing it. The non-precise way you've already heard about, sheet of paper, check for dragging. The better (more precise) way, is using a magnetic base micrometer attached to your extruder head. You can then watch the bed run-out in real time; if your 3d printer supports many configurable sections across the bed ( I know Prusa style cartesian units mostly all support quadrants) you can record the run out everywhere across the plane without any more physical work than watching the gauge and recording the results. P.S. be careful using both the micrometer and the feeler gauges on a 3d printer bed. Most work plates now-a-days are using PEI coatings that'll scrape off easily with metal-on-metal contact.
  - WrtCdEvrydy 6y ago
    > using PEI coatings that'll scrape off easily with metal-on-metal contact. Yeah, you're correct, it's a glass bed so I use it to do the 4 corners (every few months) and then use a BL touch to do a 3x3 grid on top of it.
bilbo0s 6y ago
couldn't get more simple than that. Believe it or not, that's actually a lot of the idea that drives commercial aviation design. Or used to anyway.
- KMag 6y ago
  ... and most engineering in general. Simple solutions tend to be very robust and often cost-effective.
  - noir_lord 6y ago
    and easier to troubleshoot/replace. > A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over, beginning with a working simple system. - John Gall
na85 6y ago
That's what real engineering is about: the simplest tool or process that will get the job done. Despite what we see on the web more and more, this principle applies to code too. It shouldn't be about stacking up layers of complexity for no good reason.
- Gibbon1 6y ago
  Somehow your comment reminds me of a pissing match I saw between a young aerospace engineer and an old retired one. The old guy was right in his argument that it doesn't matter what the constraints on materials and dimensions are, it that they come from somewhere and are documented. His example was designing brackets for a Indonesian construction company that was using locally sourced tropical softwoods for constructing buildings. The brackets were designed to be made with 'steel' and the tolerances were compatible with a hungover guy running a drill press.
cartoonfoxes 6y ago
They're deceptively simple. If you want to get into the history of modern manufacturing, a lot can be written about the development of gauges of accurately known dimensions.
- nitrogen 6y ago
  I went down a rabbit hole of videos last yearish about the origins of precision (that should be a searchable phrase to get started).
  - cartoonfoxes 6y ago
    Go find a PDF of "Fundamentals of Mechanical Accuracy" by Wayne R. Moore, if you haven't already seen it. That book, along with George Daniels text "Watchmaking" are some of the top inspiring works on the mechanical arts in my collection.
- noir_lord 6y ago
  Somewhat sadly a lot of the drive for that tolerance was weapons, until we could accurately make very high tolerance (for the day) parts you couldn't use parts from one rifle on another without a smith, it certainly wasn't field serviceable - this imposed a lot of maintenance overhead until they solved it properly. It seems like we really like to push the limits when it comes to shooting each other.
  - linuxftw 6y ago
    > Somewhat sadly Weapons can be used for defensive purposes. There's nothing inherently wrong with them, only how people use them. > parts you couldn't use parts from one rifle on another without a smith You cannot swap bolts in the field on most rifles. At minimum, you require a go/no go gauge. The tolerances on modern firearms are very precise.
    - int_19h 6y ago
      That the tolerances are so precise is exactly why you can do that on most modern rifles. It depends on the design - specifically, how they achieve headspace. On an AR-15, or almost any firearm with a similar bolt locking arrangement, bolts - indeed, entire BCGs - are swappable in practice, and people do that routinely without bothering with gauges regardless of what the manual says. On AK and similar designs, yeah, that's a really bad idea.

bewaretheirs 6y ago

Yep. To check tolerances, you'd need a go/no-go pair -- one that should fit, and a slightly bigger one which shouldn't.

lisper 6y ago
This is a thing that non-aviators often don't realize about aviation in general: the hard part is designing the artifacts and processes so that by the time you get around to operations, everything is routine and nothing is hard. Flying, building and maintaining airplanes seems hard, but that's mainly because of the volume of stuff you need to know, not because any single item is particularly difficult. All aircraft are built, maintained, and flown by mere mortals. (The designers, on the other hand... ;-)
- int_19h 6y ago
  It's not just aviation. Our entire industrial civilization works like that, and this is the only reason why it can work. We are surrounded by high-precision machinery even in daily life, and are completely oblivious to just how much technomagic it is - and how much historical effort went into building the industry up to the point where it can produce such things so easily and cheaply.

nabilhat 6y ago

Who even uses calipers for critical precision? Calipers are for dimensions machinists append with -ish, as in four thousandths-ish. Important dimensions deserve a micrometer, especially the feeler guage that just said you need to tell your boss to scrap a 737. Decent machine shops even have different classes of micrometer; there's the one you carry in your pocket, and then there's the fancy set locked up in your boss's office that only comes out for special occasions, like when your boss has to tell their boss to scrap a 737.

cartoonfoxes 6y ago
I see this in my own shop. Digital displays instill people with greater confidence in the measurement than is warranted. This is something of a UI fail, as the tool manufacturer (Mitutoyo) has very clearly defined measurement precision for all their metrology equipment (+- 0.001" and 0.0015" for the calipers).
- sgnelson 6y ago
  That is a very interesting observation, thank you. I've never thought about the digital vs analog in terms of actual "oh, it's digital, it's better." measurement variation. In my experience, I think you're probably right, it does seem like people may take them as "more accurate."
kayfox 6y ago
You don't scrap a 737 for some worn out parts.
- teh_klev 6y ago
  Not that I want to be pedantic, but that's a rather sweeping statement. The decision to scrap would depend on things like the number of flight hours and takeoff/landing cycles on the air frame and the number of other worn parts, hitting meantime-before-failure on large numbers of parts/assemblies, such that it may be more economical to scrap.
- doodlebugging 6y ago