xacto knife hobby blade

Just a quick revision to pggibson's knife design. I added a little built-on solid stub handle, and put a collar around the tensioner screw piece so at least I feel less likely to have my fingers slide forward and become a blood sacrifice.

Edit 12/13/2017: Second file is a longer handle version.

RESIZE (Shrink) BY 0.02545x! I don't know why my software is like that, but it is.