Boeing aircraft rivet hole fit-up specification

Boeing general spec: cannot apply more than five pounds of force to bring two parts into registry before riveting, to limit residual stress around rivet holes. Tom uses it to contrast Boeing's fatigue-driven specification with the Navy's looser fit-up tolerance.

Let me tell the Boeing story. So Boeing has a spec about fit-ups. This is not a come-along, this is sort of a Boeing spec. Boeing has a spec that when you're building an aircraft, you're going to rivet the hull to the inside ring stiffeners — submarines aren't quite this way; it's made out of a lighter material. The amount of force you can apply to bring those two into registry before you make your rivet has to be five pounds or less. That's the general spec. And this is one of the problems Boeing has — they have general specs. They like to write general specs, and sometimes a general spec doesn't fit a particular application, but nonetheless they are. So worried about the residual stresses on the skin of that aircraft, the structural engineers sitting in manufacturing say: you have to form it so that it fits together within a few thousandths, and you cannot apply more than five pounds of force to bring it into line. They can apply 15 pounds. You're applying more than five pounds on the ships here.