acturally it can be designed to use 2 bearing instead of 4, but i'm lazy to do that... it uses four 22 mm OD, 8 mm ID, 7 mm thick regular size bearings, with a regular sheet rock knife blade extra from 3d printed parts. i twist the knife holder 30 degrees so that it would be easier to print out with the printer. otherwise it does looks like a sheet rock knife, and works perfect on cutting thin stuff while protects the blade pretty well. hopingly some factory can redesign and produce something like this? watch out of the blade end, for i did not put any protection design on the sharp end. it won't kill but hurt pretty much if not be careful. otherwise, you need a screw driver to push the blade in and out, a little inconvenient from my lazy XD.
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