something you don't see every day, left-handed pipe tap
 

We were going through some cabinets in my machine shop today, cleaning and organizing.
One of the guys showed me something I have never seen before, a 3/4" LEFT HANDED national pipe thread tap.

Left hand threaded pipe? That's a new one on me.

Anyone care to explain that one?
the best I could come up with would be to keep from mixing up fuel and oxygen like on a torch but those are usually machine threads, not pipe threads.

Need a left handed pipe wrench to go with it :) Seriously though, interesting find. Could be worth something.

Pipe coupler unions are not allowed under house floors for natural gas. So, we use left-rights to join when a splice is necessary. You can buy a LR nipple to do the job at almost any supply, but to have the die would be cool.

no go: http://img.diytrade.com/cdimg/325506..._iron_seat.jpg

Oh, you have a tap. Oh well, it could be useful I suppose.