Gear finishing hob

A finishing gear hob, whose shape is worm-like, wherein:

• on the working side of the mentioned finishing hob there are cutting edges K, in the form of a continuous equally-rising spaced cylindrical helix, and wherein edges K are formed by the intersection of the rake faces A, forming the top surfaces of the worm, and flanks B, forming the working sides of the worm;
• the number of cutting edges K being equal to the thread number i of the worm, where i is a positive integer, the normal pitch P.sub.n of the working side of the worm being equal to the normal base pitch t.sub.b of the machined gear .pi.m.sub.n cos.alpha..sub.n, where m.sub.n is the normal module of the machined gear;
• and .alpha..sub.n is the normal pressure angle at a reference circle of the machined gear, and wherein the lead angle .lambda. of the helix cutting edges is given by the formula Sin.lambda.=(im.sub.n cos.alpha..sub.n)/2R where R is the radius of the cylindrical helix cutting edge K and the helix lead P of the helix cutting edge P=(i.pi.m.sub.n cos.alpha..sub.n)/cos.lambda.;
• and
• wherein the profile in the normal section of the flank B, which is a spiral surface, is a straight line inclined at angle .lambda. to the working side and extends outward in the direction of the radius.