초록 ▼

Significantly improved resistance to breaking while drilling in metal can be realized in twist drill bits having a web thickness taper which is about twice the web thickness taper specified in Standards and in common use in the industry. This creates much shallower flutes and flies in the face of co

Significantly improved resistance to breaking while drilling in metal can be realized in twist drill bits having a web thickness taper which is about twice the web thickness taper specified in Standards and in common use in the industry. This creates much shallower flutes and flies in the face of conventional wisdom in the art which holds that the web taper rate should be low to maximize the amount of flute volume available to convey chips and sawdust out of the hole. A flute length of about 1/2" less than the flute lengths specified by the Standards makes it possible to have such a large taper rate but still control variations in tolerances for the flute length. It also provides a marking zone for placing size indicia on the drill bit shank outside the portion which is, ripped by the chuck jaws of a power drill. The use of the new web taper rate, in conjunction with modifications to the tip geometry of a self-centering drill bit with pilot tip, produces a drill bit optimized both for metal and wood drilling which is strong enough to withstand the forces exerted on the bit while drilling in metal using a hand-held power drill, yet which need not be retracted from a 2.times.4 to clear sawdust prior to drilling a hole completely through the thickness of the wood.

대표청구항 ▼

[ What is claimed is:] [1.] A twist drill bit, comprising:a shank portion, a fluted portion and a tip portion adjacent the fluted portion;the fluted portion defining two flutes extending from the tip portion and terminating at the shank portion, the flutes having a predetermined flute length;the flu

[ What is claimed is:] [1.] A twist drill bit, comprising:a shank portion, a fluted portion and a tip portion adjacent the fluted portion;the fluted portion defining two flutes extending from the tip portion and terminating at the shank portion, the flutes having a predetermined flute length;the fluted portion further defining a web;the web adjacent the tip portion having a predetermined web thickness; andthe web thickness increasing from the tip portion to the shank portion at a uniform taper rate in the range of from about 0.050 inch to about 0.071 inch per inch of flute length. [32.] A Jobber-length, straight-shank twist drill bit, comprising:a shank, a flute having a flute length, and a tip;the bit defining a longitudinal axis;the flute length being determined by ASME B94.11M-1993 Standard for Jobber-length drill bits, or its current revision, whichever Standard is later;the radially-innermost point on said flute located a predetermined distance 1/2T from said axis at said tip; andwherein T increases along said bit at a uniform taper rate which is at least twice the web thickness taper specified for Type "B" drill bits by the latest revision of the NAS907 Standard. [57.] A twist drill bit, comprising:a shank portion, a fluted portion and a tip portion adjacent the fluted portion;the fluted portion defining two flutes extending from the tip portion and terminating at the shank portion, the flutes having a predetermined flute length;the fluted portion further defining a web;the web adjacent the tip portion having a predetermined web thickness; andthe web thickness increasing from the tip portion to the shank portion wherein during peak force failure the bit breaks in said shank portion.