Why the workshop always comes back with questions
The gap between what a designer specifies and what a maker needs to know.
A workshop keeps coming back with questions because the person drawing a part already carries a complete picture of it in their head, filled in with assumptions too familiar to notice, while the workshop only has what actually made it onto the page, and the gap between those two is exactly where every question comes from.
Directions to a place visited a hundred times
Giving someone spoken directions to a place visited a hundred times comes out full of gaps without anyone noticing they are there. "Turn left at the big tree" gets said without a thought, because the tree has been a fixed, obvious landmark for years to the person giving directions, and it means nothing to someone hearing about it for the first time, who has no idea which tree, or that there is more than one, or what counts as big. The listener's questions (which tree, how far past it) mark the exact points where familiarity let something essential go unsaid, and they say nothing bad about how carefully the listener was paying attention. A drawing written by someone who has lived with a part for weeks carries the same invisible gaps, obvious to the designer and blank to anyone meeting the part for the first time on the page.
What the designer knows and the page does not
A designer drawing a part has usually spent hours or days thinking about it, deciding how it will be held, how it will be assembled and what it needs to survive, and by the time the drawing is finished a great deal of that thinking lives only in the designer's head, because it felt too obvious to write down. The workshop receiving the drawing has none of that background, only the marks on the paper. Every place where an unwritten assumption was doing real work is a place the workshop cannot fill in on its own, so it asks, and each question reports back where the designer's private picture of the part and the drawing's content stopped matching. Asking is the cheapest moment for that mismatch to surface, since the alternative is a finished part made to the workshop's own guess.
This happens to careful and careless designers alike, because familiarity does the hiding. A careless designer leaves obvious gaps that stand out at a glance, while a careful one can leave gaps that look complete precisely because everything nearby was handled so thoroughly, which makes the one missing assumption harder to spot. A drawing can carry forty correct dimensions and still come back with questions, since the forty that were written down say nothing about whether every decision the workshop needs was among them. Completeness is a property of the gaps, and counting what was filled in around them does not measure it.
Reading the directions back a second time while deliberately pretending not to know the destination sometimes catches a gap before anyone else does. It rarely catches all of them, since the familiarity being guarded against is the very thing that makes unfamiliarity hard to fake.
Why experience reduces the questions without ending them
No amount of experience removes the gap entirely. A designer who has learned to write down what tripped up the last workshop simply finds the familiar, unstated assumptions turning up somewhere else in the drawing, on whatever detail felt obvious this time, which is why even seasoned drawings still come back with the occasional question, fewer of them and about different things than before. Trying to anticipate every gap in advance turns out to be close to impossible. The habit that helps most is treating every returned question as a small, specific lesson about where familiarity had been standing in for something that needed to be written down, and adding that item to the list of things checked before the next drawing goes out.