Quote:
Originally posted by Freycinet:
Mass production from assembly lines was only just getting into its stride during WWI. Most of these planes were very much made in workshops, with all the individual differences in fittings and bracings that that would entail.
It's not as bad as you might think or at least with the technology of the times it didn't have to be.

When mass producing even back before 1850 there was use of jigs which were either made at the home factory or detailed drawings sent, the first task would be the toolmakers building jigs. A jig is a frame with places to hold the workpiece and to place tools against to make the cuts. Properly even on things as large as WWI aircraft frames the use of jigs should keep errors to perhaps a centimeter or less. Certainly frame parts from the same same lines fit together, had they not then a jig would have been changed or remade.

Improperly though and in practice as sometimes happened, people didn't follow plans so well and nobody cross checked with dismal results. It was not common but did happen, more in some places where 'craft' was held in a bit too much esteem in some shops. Example is that LMG the French dumped on the US troops who wished they'd brought their own.

Look at how interchangeable so much of pistol and rifle parts were from mid-1800's on. Or steam engine parts. The technology certainly existed in WWI. Even cars, trucks and motorcycles were made for part interchangeability.