So I have read through multiple questions about how the workshop handles the various categories when it automatically scraps things to produce raw materials for projects that you are building. It has been clearly shown that anything outside of the "junk" category is safe from automatic salvage.
However, I wanted to know what happens to things in the "junk" category when they are salvaged. If something from junk gets automatically dismantled to supply some material for a project, but the project only requires one of the several pieces of material from that broken down junk, do you still get the left-over materials or are those used up as well? I know that if you manually break down junk items yourself (i.e. drop them on the ground and use the settlement interface to break them down) then all of the materials are stored in your workbench, but what happens to those materials when the pieces are broken down automatically?
Best Answer
In researching the related question How can I break items down into their components, I saw a complaint on Reddit to the effect that the extra, leftover materials get destroyed.
Why this is a common belief
Many people seem to believe this, and there's a good reason for that: it's confusing. And it's confusing for two reasons:
Go, science!
I settled the question with science. I've tested this with various items a dozen or so times using the Armor Workbench, the Weapons Workbench, and the Workshop crafting menu.
The leftover components have always (so far) appeared in the Workshop inventory, but there's sometimes a delay.
Here's one of the experiments:
Experiment
By creating the Emitter, we force the Workbench to dismantle the pencils, which liberates 2 Wood and 2 Lead.
If our Wood component count goes down, wood has been lost/destroyed. If it stays the same, our 2 "potential" units of Wood have simply been converted into 2 actual units of Wood.
Result
Our Wood component count remains unchanged. So unneeded materials are retained, just as though you'd broken the item down yourself.