Twist drill for dry drilling

A method for dry drilling utilizing a twist drill for dry drilling, said drill comprising:

• a tip portion;
• a body portion disposed adjacent said tip portion;
• a central longitudinal axis;
• said body portion having an axis of rotation lying along said central longitudinal axis;
• said tip portion being substantially cone-shaped;
• said tip portion having a base portion and a top portion;
• said base portion being substantially wider than said top portion;
• said base portion being disposed immediately adjacent said body portion of said drill;
• said top portion being disposed opposite said base portion;
• said tip portion comprising:
• a first chip face forming a portion of said conical surface of said tip portion;
• a second chip face forming a portion of said conical surface of said tip portion;
• a chisel edge arrangement configured to initiate dry cutting of a metal object to be dry drilled;
• said chisel edge arrangement being disposed between said first chip face and said second chip face;
• said first chip face having a first end disposed adjacent said chisel edge arrangement and a second end disposed opposite said first end and adjacent said body portion of said drill;
• said second chip face having a first end disposed adjacent said chisel edge arrangement and a second end disposed opposite said first end and adjacent said body portion of said drill;
• said first chip face being configured to extend monotonically away from said body portion to said chisel edge arrangement disposed on said top of said tip portion;
• said second chip face being configured to extend monotonically away from said body portion to said chisel edge arrangement disposed on said top of said tip portion;
• said first chip face being disposed to meet said second chip face at said top of said tip portion;
• and said chisel edge arrangement comprising:
• a first chisel edge portion;
• a second chisel edge portion;
• each of said chisel edge portions being disposed to extend away from each other from said central longitudinal axis;
• and said first chisel edge portion and said second chisel edge portion being asymmetric with respect to one another about said central longitudinal axis;
• said body portion comprising:
• a shank portion;
• a middle portion;
• an end portion;
• said end portion being disposed adjacent said tip portion;
• said middle portion being disposed between said shank portion and said end portion;
• a first chip flute;
• and a second chip flute;
• a first cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• a second cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• said first cutting edge and said second cutting edge being substantially symmetric with respect to one another about said central longitudinal axis;
• said first chip flute being disposed to extend along said body portion from said first cutting edge;
• and said second chip flute being disposed to extend along said body portion from said second cutting edge;
• said method comprising the steps of:
• contacting with said chisel edge arrangement a metal object to be dry drilled;
• dry drilling in a direction along said axis of rotation of said body portion of said drill;
• generating a deviation of said tip portion from the drilling direction along said axis of rotation of said body portion of said drill with said asymmetric chisel edge portions;
• producing an entrance hole with said deviation of said tip portion of said drill to produce an entrance hole larger in diameter than said diameter of said end portion of said drill to permit withdrawal of said end portion after expansion of said end portion due to further heating of said end portion during further dry drilling;
• continuing dry drilling and thereby heating said end portion, causing said end portion to expand in diameter;
• continuing dry drilling with said expanded end portion to produce a hole beyond said entrance hole;
• continuing dry drilling until a predetermined depth of said hole is reached;
• and withdrawing said expanded end portion from the metal object without substantial jamming of at least the end portion of said drill in said entrance hole.

A twist drill for dry drilling a metal object, said drill comprising:

• a tip portion;
• a body portion disposed adjacent said tip portion;
• a central longitudinal axis;
• said tip portion comprising:
• a chisel edge arrangement configured to initiate dry cutting of a metal object to be dry drilled;
• and
• said chisel edge arrangement comprising:
• a first chisel edge portion;
• a second chisel edge portion;
• said first chisel edge portion having a first end and a second end opposite said first end;
• said second chisel edge portion having a first end and a second end opposite said first end;
• said first end of said first chisel edge portion being disposed to meet said first end of said second chisel edge portion at said central longitudinal axis;
• each of said chisel edge portions being disposed to extend away from each other from said central longitudinal axis;
• and
• said first chisel edge portion and said second chisel edge portion being asymmetric with respect to one another about said central longitudinal axis;
• said body portion comprising:
• a first chip flute;
• and
• a second chip flute;
• a first cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• a second cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• said first cutting edge and said second cutting edge being substantially symmetric with respect to one another about said central longitudinal axis;
• said first chip flute being disposed to extend along said body portion from said first cutting edge;
• and
• said second chip flute being disposed to extend along said body portion from said second cutting edge.

A twist drill for dry drilling, said drill comprising:

• a tip portion;
• a body portion disposed adjacent said tip portion;
• a central longitudinal axis;
• said tip portion comprising:
• a first chip face forming a portion of said surface of said tip portion;
• a second chip face forming a portion of said surface of said tip portion;
• a chisel edge arrangement configured to initiate dry cutting of a metal object to be dry drilled;
• said first chip face being disposed to meet said second chip face at said chisel edge arrangement;
• and
• said chisel edge arrangement comprising:
• a first chisel edge portion;
• a second chisel edge portion;
• each of said chisel edge portions being disposed to extend away from each other from said central longitudinal axis;
• and
• said first chisel edge portion and said second chisel edge portion being asymmetric with respect to one another about said central longitudinal axis;
• said body portion comprising:
• a first chip flute;
• and
• a second chip flute;
• a first cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• a second cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• said first cutting edge and said second cutting edge being symmetric with respect to one another about said central longitudinal axis;
• said symmetry of said first cutting edge and said second cutting edge with respect to one another about said central longitudinal axis being defined by a plurality of points on said first cutting edge and a plurality of corresponding points on said second cutting edge, such that a straight line drawn from any one of said points on said first cutting edge to its corresponding point on said second cutting edge goes through said central longitudinal axis, and such that the distance between any one of said points on said first cutting edge and said central longitudinal axis is substantially equal to the distance between a corresponding one of said points on said second cutting edge and said central longitudinal axis;
• said first chip flute being disposed to extend along said body portion from said first cutting edge;
• and
• said second chip flute being disposed to extend along said body portion from said second cutting edge.

A twist drill for dry drilling a metal object, said drill comprising:

• a tip portion;
• a body portion disposed adjacent said tip portion;
• a central longitudinal axis;
• said tip portion comprising:
• a chisel edge arrangement configured to initiate dry cutting of a metal object to be dry drilled;
• and
• said chisel edge arrangement comprising:
• a first chisel edge portion;
• a second chisel edge portion;
• each of said chisel edge portions being disposed to extend away from each other from said central longitudinal axis;
• and
• said first chisel edge portion and said second chisel edge portion being asymmetric with respect to one another about said central longitudinal axis;
• said body portion comprising:
• a first chip flute;
• and
• a second chip flute;
• a first cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• a second cutting edge, configured to dry drill, being disposed between said tip portion and said body portion;
• said first cutting edge and said second cutting edge being substantially symmetric with respect to one another about said central longitudinal axis;
• said first chisel edge portion comprising a first section having a first radius of curvature;
• said second chisel edge portion comprising a second section having a second radius of curvature;
• said first radius of curvature having a different radius than said second radius of curvature;
• said first chip flute being disposed to extend along said body portion from said first cutting edge;
• and
• said second chip flute being disposed to extend along said body portion from said second cutting edge.

A method for dry drilling utilizing a twist drill for dry drilling, said drill comprising a tip portion;

• a body portion disposed adjacent said tip portion;
• a central longitudinal axis;
• said tip portion being substantially cone-shaped;
• said tip portion having a base portion and a top portion;
• said base portion being substantially wider than said top portion;
• said base portion being disposed immediately adjacent said body portion of said drill;
• said top portion being disposed opposite said base portion;
• said body portion having an axis of rotation lying along said central longitudinal axis;
• said body portion comprising:
• a shank portion;
• a middle portion;
• an end portion;
• said end portion being disposed adjacent said tip portion;
• said middle portion being disposed between said shank portion and said end portion;
• said method comprising the steps of:
• contacting with a chisel edge arrangement of a drill a metal object to be dry drilled;
• dry drilling in a direction along said axis of rotation of said body portion of said drill;
• generating a deviation of said tip portion of said drill from the drilling direction along said axis of rotation of said body portion of said drill with said chisel edge arrangement;
• producing an entrance hole with said deviation of said tip portion of said drill to produce an entrance hole larger in diameter than said diameter of said end portion of said drill to permit withdrawal of said end portion after expansion of said end portion due to further heating of said end portion during further dry drilling;
• continuing dry drilling and thereby heating said end portion, causing said end portion to expand in diameter;
• continuing dry drilling with said expanded end portion to produce a hole beyond said entrance hole;
• continuing dry drilling until a predetermined depth of said hole is reached;
• and
• withdrawing said expanded end portion from the metal object without substantial jamming of at least the end portion of said drill in said entrance hole.