PURPOSE: To obtain the internal circumference of a bore, of which accuracy of finished surface is high, even when a spindle is fed in high speed, by providing multi-edges to a cutting edge part, in the titled tool having fixed edges which are made of sintered body of ultra-hard material.
CONSTITUTION: The boring work to a work W is performed in such a manner that a spindle 10 is advanced as it is revolved, and a tool 11 is inserted into a bore Wa which is previously formed, while machining oil is fed into it from feed ports 22 and 23. The bore Wa, into which machining oil is fed, is bored by fixed cutting edges 16 which are made of sintered body of ultra-hard material, and then, the diameter of a bore is enlarged. During this time, an extraordinary wear of cutting edges 16 and seizing of a bore Wa are prevented by the machining oil fed from feed ports which are provided in the front and the rear positions of cutting edges 16. A chattering phenomenon and a deflection will not occur in a spindle 10, when it is fed in high speed, because fixed cutting edges 16 are composed of multi-edges having more than 3 pieces of edge at least, to the circumferential direction. In addition, the cutting edges 16 are provided with surfaces 16a of external diameter, having a length to the axial direction, so that the surface of internal circumference of a bore Wa can be finished in high accuracy.
NAGAKURA TOORU
TSUKAMOTO RIYUUICHI
