Last edited by Chuck Thoits; 04-30-2009 at 12:26 AM.
It could be worse You could be on fire.
That is a Metal Lathe tool.
It's used for turning threads. My old landlord showed me one just like it at his shop a couple weeks ago.
It's a quick change treading tool for a metal lathe. hard to tell exactly what type quick change tool post is fits though.
Near as I can gather it looks like it goes into any tool holder that can support whatever thickness that little tongue is on the side. It also appears to have a shim on that (some kinda metal trip with two screws countersunk) tongue, too. Likely to get the cutting point right at Center on the lathe.