A disposable
cutting insert for a boring cutter can reduce the roughness of a
cut surface and achieve a mirror-like surface effect. The disposable
cutting insert has a long curved blade edge, and the
radius vertex of the long blade edge is deviated slightly from an external side of a vertex of the
radius of
cutting edge. A short curved blade edge is formed between the
radius arc vertex and the radius arc vertex of the cutting edge. The
vertical distance of the short curved blade edge is greater than the feed rate. The cutting edge cuts the work piece and the short curved blade edge can scrape a small size of material precisely for scraping the peak
cut by the cutting edge and lower the height of the peak, so as to lower the
surface roughness, and produce a mirror-like surface for an internal periphery of a bored hole.