3 ms·
People (usually on the internet) act like you "need" drawings. You don't. Tolerances are almost never bespoke except in the rarest occasions of cutting edge g
by potato3732842 1y ago
People (usually on the internet) act like you "need" drawings.
You don't. Tolerances are almost never bespoke except in the rarest occasions of cutting edge green field development.
You can literally buy an old book (the info is all on the internet too but not in one place) and skim through thousands and thousands of pages that tell you what different classes of tolerance for different applications are. You don't need to know what they spec'd. You just need to know what the part was and how it was used.
The thought process goes like "This worn the f out coupling is .9443 inches major diameter, so it was a 1" (nominal) coupling, and it must slip under load, so I will use a class-whatever fit, and the tolerances for that are +/-.0gfy"
An imprecise drawing is also a sufficient starting point for the process.
And like 30% of the time then you get half way through figuring out how to set it up and realize that you can literally just buy whatever you're looking for at tractor supply or Alibaba or whatever and modify it slightly.
- WalterBright 1y agoAirplanes aren't like that. Sure, bearings and bolts are standardized. But the rest is full custom.
- bluGill 1y agoairplanes too often were machined to fit. Where tollerances were used you got intrechangable parts and so could maintain it in the field - but that took a lot of skilled engineers.
- WalterBright 1y agoBoeing put in a lot of effort to specify the tolerances so they fit without needing rework. Engineers are only called in when the rework is not the same as the specification.
- bombcar 1y agoOne of the hardest parts of all this is that you can have a bunch of parts, all in tolerance, but since they’re all on the small side of the tolerance, they add up to something out of tolerance.
- bluGill 1y agoThat is something boeing but a lot of effort into, but many airplane makers didn't.
- WalterBright 1y agoSpecifying those tolerances was part of my job. It is not hard, it is simple arithmetic. Well, with some trig. I was amazed at the other engineers who would simply pick "good engineering tolerance" and never do the arithmetic. Once my lead engineer noticed that I sized the jackscrew length with a tolerance of 30.017 to 30.033 (I'm making up the numbers, as I don't recall the exact numbers). He said why not make it a nice round 30.02 to 30.03? I said that if the jackscrew came in at 30.018, it wouldn't need to be rejected and sent to rework. He thought for a moment, and said "carry on". LOL