In aerospace, if Alice needed a hole drilled and didn’t care about tolerance, she’d have specified a class III hole per her company’s hole drilling process and

In aerospace, if Alice needed a hole drilled and didn’t care about tolerance, she’d have specified a class III hole per her company’s hole drilling process and gone to get a latte. The process document has the appropriate tolerance called out for each diameter and class. Not every hole needs a tight tolerance, depending on the loading and assembly methods. And manufacturing prefers a standard tolerance range to be specified to enable consistency in manufacturing operations, rather than some weird lopsided super precise tolerance callout. So you determine the largest tolerances that will meet your design requirements, then select a fit class from the manufacturing standard that meets your tolerance requirement.