A thread repair tool for rethreading a blind tapped hole having damaged threads above undamaged threads of the hole, including: a shaft having a plurality of curved surfaces that extend from a top end of the shaft to a bottom end of the shaft, the plurality of curved surfaces being concave with respect to an exterior perimeter of the shaft; and wherein the shaft has a plurality of corner portions, each one of the plurality of corner portions being located in between two of the plurality of curved surfaces, a first pair of the plurality of corner portions extending from the top end to the bottom end, and a second pair of the plurality of corner portions having a threaded area proximate to the bottom end, the first pair of the plurality of corner portions being adjacent to each other and the second pair of the plurality of corner portions being adjacent to each other.