Fuji Seiko Limited

Manabu Shimizu

Akio Fukui

Kiyotaka Shiga

Tsunehisa Yamashita

Masaki Yasuhara

Nobuya Matsushita

A burnishing drill includes a cylindrical shank and a drill body connected to the shank. Drilling edges, first reaming edges and second reaming edges are formed on a first reduced diameter portion, a second reduced-diameter portion and a third reduced-diameter portion respectively located at a foremost end of the drill body. Each of the reaming edges is inclined with respect to the longitudinal axis of the drill at an angle which is set so as to be within a range of between 5.degree. and 30.degree.. During a boring operation using the drill, a hole is drilled by the drilling edges and the drilled hole is then worked by the first reaming edges and the second reaming edges to provide a smooth inner wall in the drilled hole. Since each of the reaming edges is formed to extend radially outward from the foremost end of the drill and incline axially in the rearward direction at a relatively small angle, the centering property can be greatly improved.

Burnishing drill

A burnishing drill includes a cylindrical shank and a drill body connected to the shank. Drilling edges, reaming faces and reaming edges are formed on a first reduced-diameter portion, a second reduced-diameter portion and a third reduced-diameter portion located at a foremost end of the drill body respectively. The reaming faces which are located axially at backward positions of the drilling edges and the reaming edges extend radially outward from the foremost end of the drill and incline axially in the rearward direction, and also extend radially outward and incline in the rearward direction with respect of the rotational direction. Since an inner surface of the hole drilled and reamed by the drilling edges and the reaming edges can be further smoothed by the reaming faces, the surface roughness of the finished hole can be much improved.

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Toyota, Japan

Manabu Shimizu