3D-metal printed reamer.
https://diqn32j8nouaz.cloudfront.net...a_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...241#post176855
https://www.homemadetools.net/forum/...500#post166543
https://www.homemadetools.net/forum/...184#post214598
https://www.homemadetools.net/forum/...370#post161818
https://www.homemadetools.net/forum/...392#post200474
