Today was screw day. The first part is the same for all things round: the metal lathe.
But some things are not round. The nuts need a screwdriver slot. I start with a metal handsaw, more or less in the middle. Widen up the slot a bit with a file.
The screw also needs filing. Under the head, I need a square shank, so the screw won't rotate when tightening the nut. No meassuring, just eyeballing it.
And that's it. Nuts and bolts.