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Stepped drill construction

  • US 4,582,458 A
  • Filed: 08/09/1984
  • Issued: 04/15/1986
  • Est. Priority Date: 08/09/1984
  • Status: Expired due to Fees
First Claim
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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.

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