Basically a Sen is like a draw knife but swords blades. As a metal on metal operation I found it kinda crazy. "We're supposed to cut this metal blade with another metal blade.... in a woodworking way?"
After making the tool and trying it for a bit, we got kinda bored by it and opted into modern power tools and such to shape the blade, but it was a cool venture into sword making history. Here's an article about Sen making and what they're used for. (There seems to not be a wikipedia article about the Sen... challenge anyone?)
|here's one from the article linked above|
|Russ did the main grinding on the wheel, then went to belt|
|here's the sword partially hammered out|
|that crazy idea of scraping swords in action|