Scott,

It is called a "Therad Chaser" they make them in all sizes ... you may
find them at Enco.com or other machine catalogs.

JK


Scott wrote:
I can't remember the exact name of the tool, but it's made to repair
internal threads that are damaged. Basically looks similar to a piston
ring expander with changeable dies that attach at the ends. Then all
you do is set the dies into the threads, squeeze the handle a bit to
give the dies some pressure to stay in the threads and spin the tool around.

Scott