Patent ID: 7178433

Claim:
A processing apparatus, comprising: a diamond tool having a cutting edge made of a diamond and a rake face including a first edge portion shaped in a straight line, a second edge portion shaped in an arbitrary shape and a third edge portion formed between an end portion of the first edge portion and an end portion of the second edge portion and having a first end portion and a second end portion, wherein a tip end peak point of the rake face is located on the third edge portion; a holding member to hold the diamond tool; a shifting device to shift relatively at least one of the rake face of the diamond tool and a portion of an article to be processed in a direction in which the rake face and a portion of the article cross with each other; wherein the first end portion of the third edge portion continues to the end portion of the second edge portion, and wherein when the first edge portion is made as X axis, the tip end peak point of the rake face is made as an intercept ( 0 , y) on Y axis, and the rake face is projected in the first quadrant on an X-Y plane, the shape between the end portion of the first edge portion and the end portion of the second edge portion is asymmetric around a straight line which passes at the intercept and is parallel to X axis and the shape is shaped to be not a straight line such that Y value of a point on the shape increases as X value of the point increases.