Abstract: A tapered slot end mill comprising a shank and a tapered section having a polygonal shape and disposed at the end of the shank, the tapered section being adapted such that the edge formed at each vertex of the polygonal shape along the axis of the end mill is tapered to have a smaller diameter at the end of the end mill and has a helix form, a pair of end cutting edges formed symmetrically at the ends of the edges, with a part of the edge included in the end cutting edge, and a pair of peripheral cutting edges are respectively provided adjacent to the end cutting edges via rake angle surfaces, and the end mill being characterized in that the helix is formed in the direction opposite to the rotating direction of the end mill.

Abstract: An end mill for finishing the face or side of hard work comprising a shank, a plurality of helix cutting edges on the periphery of the end mill, and a cutting edge section perpendicular to the axis of the end mill having a polygonal shape with three or more angles, the cutting edge being the edge formed at each vertex of the polygonal shape along the axis of the end mill and being circumscribed by an imaginary cylinder, and the end mill being characterized in that the helix direction of the cutting edge is identical to the rotational direction of the end mill. The end mill of the present invention is able to cut the face or side of the hard work at a feed rate several times higher than that of conventional end mills. Moreover, the end mill of the present invention assures superior surface roughness of finished work.