Twist drill for drilling having a replaceable drill tip, and a replaceable drill tip for use in a twist drill

A replaceable drill insert configured to be removably attached to a drill shaft, said drill insert comprising:

• a drill tip being configured to cut an object;
• an extending portion being configured to extend into a recess in a drill shaft to removably attach said drill insert to a drill shaft and to hold said drill insert in a drill shaft during drilling;
• said extending portion comprising solely two projections disposed opposite and separate from one another;
• each of said two projections being in the shape of a portion of a screw thread and being disposed to run less than 180 degrees around a section of the perimeter of said extending portion;
• each of said two projections being configured to project into and engage a corresponding grooved portion in a recess in a drill shaft;
• and
• said drill insert being configured to be relatively rotated with a drill shaft, upon insertion of said drill insert into a recess in a drill shaft, less than 180 degrees to engage a grooved portion of a recess in a drill shaft with a corresponding one of said projections to screw together said drill insert and a drill shaft to tighten and sufficiently firmly seat said drill insert in a drill shaft to prepare a drill for drilling.

A replaceable drill insert configured to be removably attached to a drill shaft, said drill insert comprising:

• a drill tip being configured to cut an object;
• an extending portion being configured to extend into a recess in a drill shaft to removably attach said drill insert to a drill shaft and to hold said drill insert in a drill shaft during drilling;
• said extending portion comprising at least one projection;
• said at least one projection being in the shape of a portion of a screw thread and being disposed to run less than 180 degrees around a section of the perimeter of said extending portion;
• said extending portion comprising at least one non-threaded mating surface disposed between said drill tip and said at least one projection;
• said at least one mating surface forming a substantial portion of said extending portion along the longitudinal axis of said extending portion;
• said at least one mating surface being configured to contact a substantial portion of a complementary non-threaded mating surface in a recess in a drill shaft;
• said at least one projection being configured to project into and engage a grooved portion in a recess in a drill shaft;
• and
• said drill insert being configured to be relatively rotated with a drill shaft, upon insertion of said drill insert into a recess in a drill shaft, less than 180 degrees to engage a grooved portion of a recess in a drill shaft with said at least one projection to screw together said drill insert and a drill shaft to tighten and sufficiently firmly seat said drill insert in a drill shaft to prepare a drill for drilling.

A twist drill comprising:

• a drill shaft;
• a replaceable drill insert being removably attached to said drill shaft;
• at least one chip flute;
• said at least one chip flute comprising a first chip flute portion disposed on said shaft and a second chip flute portion disposed on said replaceable drill insert;
• said drill shaft comprising a recess configured and disposed to receive said replaceable drill insert and to hold said replaceable drill insert during drilling;
• said replaceable drill insert comprising:
• a drill tip being configured to cut an object;
• and
• an extending portion being configured to extend into said recess in said drill shaft to removably attach said drill insert to said drill shaft and to hold said drill insert in said drill shaft during drilling;
• said extending portion comprising at least one projection;
• said at least one projection being in the shape of a portion of a screw thread and being disposed to run less than 180 degrees around a section of the perimeter of said extending portion;
• said recess of said drill shaft comprising at least one grooved portion;
• said at least one grooved portion being disposed to run less than 180 degrees around a section of the interior of said recess;
• said at least one projection being configured and disposed to project into and engage said at least one grooved portion in said recess in said drill shaft;
• said replaceable drill insert and said drill shaft being configured to be relatively rotated, upon insertion of said replaceable drill insert into said recess, substantially less than 180 degrees to engage said at least one grooved portion, in a screwing motion, with said at least one projection to screw together said replaceable drill insert and said drill shaft to tighten and sufficiently firmly seat said replaceable drill insert in said recess to prepare said twist drill for drilling;
• said drill shaft has a central longitudinal axis;
• said replaceable drill insert has a central longitudinal axis configured to be aligned with said central longitudinal axis of said drill shaft;
• said shaft comprises a first end and a second end disposed opposite said first end;
• said first end of said shaft comprises a shank portion configured to be inserted into and held by a chuck;
• said at least one chip flute comprises at least a first chip flute and a second chip flute;
• said second end of said shaft comprises said recess;
• said recess comprises a bottom wall and at least one side wall disposed to extend in a substantially axial direction away from said bottom wall;
• said extending portion of said replaceable drill insert comprises a flat end face configured and disposed to engage said bottom wall of said recess;
• said drill shaft comprises an end face disposed about said recess;
• said replaceable drill insert comprises a bearing surface disposed about said extending portion and transverse to said central longitudinal axis;
• said bearing surface is configured to be complementary to said end face of said drill shaft and is configured and disposed to contact and rest against said shaft end face;
• said at least one side wall comprises said at least one grooved portion;
• the shape of said at least one grooved portion of said recess is complementary to the shape of said at least one projection of said extending portion;
• said at least one grooved portion is disposed to run substantially less than 180 degrees around a section of said at least one side wall from said first chip flute to said second chip flute;
• said at least one projection is disposed to run substantially less than 180 degrees around a section of the perimeter of said extending portion from said first chip flute to said second chip flute;
• said at least one projection forms a substantial portion of said extending portion;
• said extending portion comprises at least one non-threaded mating surface disposed between said drill tip and said at least one projection;
• said at least one mating surface forms a substantial portion of said extending portion along the longitudinal axis of said extending portion;
• said at least one mating surface is configured and disposed to contact a substantial portion of a complementary non-threaded mating surface in said recess;
• said at least one projection is in the shape of a portion of an asymmetrical screw thread;
• said at least one projection has a first surface and a second surface disposed at an angle with respect to each other;
• said first surface is disposed to make a first angle with respect to the longitudinal axis of said extending portion;
• said second surface is disposed to make a second angle with respect to the longitudinal axis of said extending portion;
• said first angle is greater than said second angle;
• said first surface is disposed to slope axially toward said drill tip;
• said first surface is configured and disposed to engage a first complementary surface of said at least one grooved portion of said recess;
• said extending portion comprises at least one other non-threaded mating surface disposed between said second surface and said end face;
• said at least one other mating surface is configured to contact a substantial portion of a complementary non-threaded mating surface in said recess;
• said bearing surface comprises a recess configured to engage a complementary rotation stop surface which projects from said end face of said drill shaft;
• said first surface forms an angle with respect to said central longitudinal axis of 90° to 45°;
• and
• said at least one projection comprises solely two projections disposed opposite and separate from one another on said extending portion.