Drum thickness sander for thinning leather.

[LederMaschinist]

I've though about building a hand cranked machine from scratch.  I actually do a lot of grinding and cutter work in my day job, and in my opinion the blade would actually be the easy part.  I thought about modifying a purchased rolling mill used for jewelry making and such.  It basically already has everything but the splitting blade already there.  The bottom roller would have to be textured for grip, and perhaps mounted on springs to apply even pressure on leather that's uneven in initial thickness.

The other route I have considered is basically a guided "plane" where the blade follows closely behind a roller that would apply pressure to the leather to hold it in place and and ensure it's pressed flat against the work surface.  The plane would ride on a rail suspended over the work surface and would shave a strip about 1" wide.  The working idea would be you lay the piece of leather on the work surface, grain side down, and pull or push the plane across the leather.  Then you'd advance the leather over slightly less than the width of the cutter, and take another pass.  You'd basically thin the leather in 1" wide passes more or less "mowing" it thinner.  Even a large piece would go quickly.  And size would only be limited by the length of the rail that the plane rides on.  I'd use inexpensive linear rail with a bearing block to guide the plane.