What is this?

[lebaron]

What is this used for. There is no name on tool. Has a sharp edge.

[Papaw]

That is an adze.
http://en.wikipedia.org/wiki/Adze

[lebaron]

Many thanks.

[Branson]

It's an adz, but an odd one.  The hammer head makes me think of a cooper's adz, but the deep curve of the blade looks like a bowl adz instead.  Yet bowl adzes are curved like gouges.   What it would be excellent at doing is hollowing out canoes.  I had to do that once, and forged a carpenter's adz into a curve like yours. 

It's definitely a special use adz of some sort,

[Billman49]

Cooper's trussing adze....

[amertrac]

Cooper's trussing adze....

I think you are right i saw amish use them to fit the beams when building a barn bob w.

[tompepper]

the amish usually use a foot adz on barn beams.that adz is used in barrel making,thus a coopers adz.

[Branson]

My first thought on seeing this adze was cooper's trussing adze.  But the acute angle of the blade bothered me.  I had never seen one quite like this.  Outils Anciens ( http://outils-anciens.xooit.fr/t4514-Vieux-Marche-Bruxelles-Septembre-2012.htm?start=90 ) gives another view.  Attached are
photos of three examples of a "cooper's rounding adze" and the relevant passage from Salaman. 

This is a cooper's rounding adze rather than a trussing adze.

[Branson]

The adze is a wonderful tool.  I have a number of them, from the cooper's trussing, two sculptor's adzes, several foot adzes, a couple of shipwright's adzes, and even a gutter adze (shaped like a giant gouge, for carving out wooden gutters).   Once spent 14 days with a foot adze, 7 hr per day, working beams for a new building that had to duplicate the 1930s beams in the main house.

Before the invention of the plane, the adze was the tool used for smoothing wood.  There's a drawing of a Greek carpenter (from an ancient Greek ceramic) that shows him using a rather light adze to smooth a piece of wood.  There is a thong attached to the adze that is tied to his shoulder to contain the arc of the swing so that each stroke is consistent.

[amertrac]

the amish usually use a foot adz on barn beams.that adz is used in barrel making,thus a coopers adz.

the foot adz shaped the beam the littlt adz is used to fit the beams to a tight  fit  bob w.