To enhance the cutting ability of a blade through diminished cutting resistance and thus prevent the occurrence of burs, and also maintain the cutting ability for a long period of time by restraining the abrasion of the blade and thereby prevent material from burning.

The flash bit 1 is formed of a bit main body 2 and a substantially cylindrical contact part 3 brazed to its tip end. The contact part 3, when external plate of the flash panel is cut off along the internal wall face of a frame body, comes in contact with the frame body. The bit main body 2 includes a cutting part 4 and shank part 5. The cutting part 4 is configured in two stripes by an each pair of twisted sides 41 and twisted grooves 42, and also in a left spiral so as to introduce cut debris toward the contact part 3 during rotation. Also, formed at the rotation side of the twisted sides 41 are outer circumferential cutting blades 411 having a focus of the same diameter as an outer circumferential face 31 of the contact part 31.