As you may have read below leather has been introduced and it has officially invaded the bindery. As you should know by this post, leather requires paring. Shaving it down thin thin thin is crucial. It's workability is dependent on how thin and even it is pared down. While the Scharfix can shave a large amount off, knives are needed to get those tiny edges smooth.
Long story short - One cannot pare leather without proper knives. Good knives are very expensive. Mission - I make English and Swiss Style Paring knives on my own.
I spent about week grinding away hack saw blades. Buzzing and covered with metal bits and a bit of my right thumb shaved off, I felt powerful, I felt gross, but I now have and use two 1.25 knives (English and Swiss) and three 1 inch knives (2 English, 1 swiss). I also made three knives for classmates. I fear no belt sander.
Last fall when knife and tool master Jeff Peachey came to North Bennet he taught us how to make Lifting knives, which are useful when repairing books. I made a few of those as well.
I hope you enjoy knives as much as I do.