Thread cutting tools

Claim 1

A thread cutting tool comprising a body, four lineal arrays of teeth on the body substantially equidistant from the longitudinal axis thereof and angularly spaced from each other by 90*, a chamfered section on the teeth at the forward end of the body, one oppositely disposed pair of such lineal arrays having a series of long teeth interspersed with a series of short teeth, the other oppositely disposed pair of such lineal arrays having teeth of uniform length which are shorter than the long teeth in the first mentioned pair of lineal arrays, a land on each of the teeth in the first mentioned pair of lineal arrays having a lateral width which may vary from 0.003 to 0.005 inch, an inwardly and rearwardly disposed chip clearance surface on each tooth of the four lineal arrays extending from the trailing edge of the land thereon to a point adjacent the heel of such tooth which is at least 0.015 inch below the root thereof, and a flat cutting face on each tooth in the four lineal arrays extending at least 0.020 inch below the root of the tooth, said cutting faces on the teeth of each pair of lineal arrays being disposed at substantially right angles to a transverse medial plane through the other pair of lineal arrays.