What is this tool?

[oberst]

A friend was asking me what this is used for - I told him the fellas at GJ would figure it out in two shakes of a lambs tail....

I hope so!

 

[cgrutt]

Looks sort of like half of a brake line flaring tool but the ones I've seen are split in center like this

 

[slip knot]

Dowel cutter.

 

[turbowoodworker]

I was thinking dowel cutter too.