Rotary cutting tool

Claim 1

A rotary cutting tool having at an axial end surface thereof two cutting edge lines arranged substantially in a diametral plane extending through a center of rotation of the tool, one cutting edge line having an inner cutting edge section (101) adjacent to the center and the other having an inner noncutting edge section (21) adjacent to the center, in which the cutting edge line (20) having the inner noncutting edge section (21) has one intermediate noncutting edge section (22) and the cutting edge line having the inner cutting edge section (101) has at least one intermediate noncutting edge section (11), said at least one intermediate noncutting edge section (11) of the cutting edge line having the inner cutting edge section is located within a radius from the center larger than a radius from the center of the inner noncutting edge section of the other cutting edge line, said intermediate noncutting edge section (22) of the cutting edge line having the inner noncutting edge section being located within a radius from the center corresponding to a radius from the center of an outermost cutting edge section (102) of the cutting edge line having the inner cutting edge section, characterized in that basic dimensions and locations of cutting edge section and noncutting edge sections arranged along both cutting edge lines are determined so as to substantially satisfy the following two equations: b+c-d-e+1=0 b.sup.2 +c.sup.2 -d.sup.2 -e.sup.2 +1=0 where: b=r B /r F c=r C /r F d=r D /r F e=r E /r F' r B , r C , r D , r E , r F and r G respectively indicating a radius from the center axis (0 0) at respective points, B 2 , C 1 , D 1 , E 2 , F 2 and G 1 in both the cutting edge lines, rendering the relative condition below, r.sub.B ≦r.sub.C <r.sub.D ≦r.sub.E <r.sub.F ≦r.sub.G and determining the dimensions and locations of cutting edge sections and noncutting edge sections.