Stepped drill construction
First Claim
1. Drill bit of stepped construction having a shank at one end and a series of generally cylindrical outer surfaces of incrementally decreasing diameter from the shank end to the outer end thereof, said drill bit comprising a beveled conical surface interconnecting each adjacent pair of cylindrical surfaces, at least two flutes machined into opposite sides of the drill bit to provide at least two cutting edges for each diameter defined by the intersection of one surface of each of said flutes, each of said cylindrical surfaces and each of said conical surfaces, a raised portion on each of the conical cutting edge surface, said raised portion having a tapered back relief over an acute angle which is substantially less than the peripheral extent of said conical surfaces.
2 Assignments
0 Petitions
Accused Products
Abstract
Drill bit for drilling holes of different diameters which has a series of cylindrical outer surfaces of increasing diameter from the outer to the inner end of the drill bit. A beveled conical surface interconnects each adjacent pair of cylindrical surfaces. At least two flutes are machined at two circumferentially spaced locations to provide two cutting edges on each diameter of the drill. At each cutting edge the cylindrical surfaces are relieved radially and the conical surface is relieved axially over an acute circumferential angle. The major peripheral portions of the cylindrical and conical surfaces for each diameter are respectively concentric to the axis of the drill and of zero pitch angle.
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Citations
6 Claims
- 1. Drill bit of stepped construction having a shank at one end and a series of generally cylindrical outer surfaces of incrementally decreasing diameter from the shank end to the outer end thereof, said drill bit comprising a beveled conical surface interconnecting each adjacent pair of cylindrical surfaces, at least two flutes machined into opposite sides of the drill bit to provide at least two cutting edges for each diameter defined by the intersection of one surface of each of said flutes, each of said cylindrical surfaces and each of said conical surfaces, a raised portion on each of the conical cutting edge surface, said raised portion having a tapered back relief over an acute angle which is substantially less than the peripheral extent of said conical surfaces.
Specification