My first 6 months sewing signatures vs my next 6 months, the difference was one cheap tool
For my first 6 months I was folding signatures with a bone folder and guessing where the crease should land, and my spines were always lumpy on the fore edge. Then a guy named Ray at a bindery in Toledo showed me a $12 teflon folding bone, and within 2 weeks my signatures sat flat enough that trimming was almost boring. Anyone else notice the crease is where 90% of your swell problems start?
The teflon folding bone thing cracks me up because I did the opposite for way too long. I thought the bone folder was just a bone folder, so I used this cheap plastic one that came in a kit and then acted shocked when my folds looked like a dog chewed them. My first batch of signatures was so bad the crease wandered around the page like it had a mind of its own. And yeah, you are dead right that the crease is where the swell problems start, because a bad fold throws off the whole spine and then you are fighting the thing at the sewing frame. I finally switched to a real bone with a proper edge and it was like night and day. Still took me another month to stop folding them with my thumbs though, old habits are stubborn.