Boeing is having a rough time of it right now, with parts falling off its planes left, right and center. Just last week, a wheel came loose and smashed through a car, and earlier this year the door from a 737 Max aircraft broke off mid-flight. That mid-air disaster sparked an audit from the Federal Aviation Administration, which has gone far from well.
Once again this is a question of tolerance. It could be a place you only care about minimum clearance. If the spec is for a gap of at least 15 mil then a pack of 30 mil key cards makes for a bunch of cheap easily replacable go/nogo gauges with enough leway that even a worn one won’t put you under spec.
I’m most familiar with IPC standards for electronics but even in the most critical class 3 applications there are plenty of spots where the standards are effectively gauged by eyeball let alone with even a makeshift tool because those specific specs aren’t that critical for the application.
I’m also Class 3 certified and where I come from inspection will absolutely measure clearances if it’s not obviously within spec. And even then there are many that still do just to cover their own ass. God help them if QA steps in and gets a different measurement.
I have no doubt different facilities run differently. Just look at Boeing. But don’t assume they’re all run like a circus just because you worked somewhere that doesn’t do things by the book.
I’m not saying we played fast and loose with the spec. I’m saying that there are plenty of places where the actual spec doesn’t use numbers and it is a judgement call for example minimum lead protrusion.
There are also plenty of places where a number is given but it is not possible to measure such as barrel fill on through hole components. In those situations an inspectors best bet is to eyeball it and if it’s even questionable to rework and correct the process so it isn’t. You don’t eyeball it when it’s close, but you also don’t need to measure, for example, lead protrusion on every lead when they all apear to be definitely under 1.5mm.