An object of the present invention is to provide a drill bit capable of easily drilling a drill hole that has no rifling, and has high circularity, can be easily positioned, the drill bit comprising a cutting blade tip which is composed of a block body of cemented carbide, three cutting blade portions are formed circumferentially equidistantly around the cutting blade tip, a connection line between a cutting surface 5 and a flank surface 6, said cutting and flank surfaces being formed in each said cutting blade portion 4a, 4b, 4c, acts as a main cutting edge 8 whereas a connection line between a connection surface 7 and said flank surface 6 acts as an auxiliary cutting edge 9, said main cutting edges 8 and said auxiliary cutting edges 9 cross at a blade tip point 10 so that said blade tip point 10 is shaped like a peak with no chisel edge, each said auxiliary cutting edge 9 lies on a line extending from said main cutting edge 8 of a said cutting blade portion located opposite across said blade tip point 10, and each of said main cutting edge 8, said auxiliary cutting edge 9, and a connection line between said connection and cutting surfaces 7, 5 crossing at said blade tip point 10 extends in a straight line.

The invention relates to a drilling tool (1), in particular for working concrete, rock, masonry and suchlike materials, having a tool head with cutting body (5) which has at least one front rake face (9, 10), at least one rear flank ([lacuna] 18) and at least one front-end cutting edge (7, 8), the cutting edge (7, 8) separating the rake face (9, 10) and the flank ([lacuna] 18). In this case, the rake face (9, 10) is formed by at least two cutting faces (11, 13; 12 [lacuna]) merging into one another at at least one second cutting edge (15, 16).

Drills, particularly rock drills, with a chisel shank and a drill head with at least one drill bit or tool bit on a face pointing in a feed direction have the tool bit formed of at least one cutting edge provided on the face side between a rake surface and a free surface with the rake surface being in the direction of rotation of the drill and being ahead of the cutting edge. The free surface has at least a portion which extends into the drill bit over at least one sub-area to form a concave depression.

A spot drilling tool includes a drill holder and an insert removably mounted to the holder. The insert is a standardized part configured to support a drill point in a predetermined position forward of the drill holder and centered on the rotational axis of the drill holder. The drill point has two flutes and two substantially conical land surfaces extending between the flutes. The land surfaces have centers of curvature offset from the rotational axis of the insert to provide radial clearance for the trailing portion of the land. A chisel edge at the tip of the drill point is supported by a tapered web defined between the diagonally opposed and offset flutes. Linear cutting edges are formed at the junction of a planar flute surface and the conical land surface. The cutting edges define a narrow included point angle of between 50.degree. and 80.degree..

A roof bit blade insert for use in mining and other associated applications. The blade defines two opposing faces, each having a leading end and a trailing end. The blade defines an indexed protrusion disposed at either or both of the leading and trailing ends of each face. A centered protrusion is defined on several embodiments. Each of the protrusions are provided to strengthen the blade and to assist in centering the blade in a drill body slot. The protrusions defined by the leading and trailing ends of the blade are defined by either an arcuate configuration, a compound curve, an outward taper from the center of the blade, or a selected location along the leading end, to the outer edge thereof. The drill body defines a transverse slot for mounting the blade, the slot having opposing parallel faces adapted to loosely receive the blade such that it is centered therein.