Helically fluted twist drill device

A helically fluted twist drill device for cutting materials, said device comprising:

• a cylindrical core having a first diameter, a longitudinal axis and a first and a second extremity, said second extremity defining a cutting point;
• at least three portions extending helically outwardly away from said core so that said portions define a second diameter, said portions being arranged such that adjacent portions define therebetween a helical flute;
• each of said flutes having a flute surface which is of S-shaped configuration when viewed as a cross section disposed normal to said longitudinal axis, said cross section being viewed in a direction from said first towards said second extremity;
• each of said portions further defining a helical bore connected to a source of a cutting fluid for permitting a flow of the cutting fluid through said bore towards said cutting point, the arrangement being such that in use of said device, the cutting fluid conveys the materials away from said cutting point through each flute;
• said first diameter having a dimension within a first range which is 20-35% of a dimension of said second diameter;
• said second extremity of the drill device being of cusp-shaped configuration for defining said cutting point;
• said drill device including:
• a first member which extends from said first extremity of said core to between said first and second extremities of said core;
• a second member secured to said first member, said second member extending coaxially from said first member to said cutting point:
• and
• a fastener for removably fastening said second member to said first member such that when said cutting point becomes worn, said second member is replaced.

A helically fluted twist drill device for cutting materials, said device comprising:

• a cylindrical core having a first diameter, a longitudinal axis and a first and a second extremity, said second extremity defining a cutting point;
• at least three portions extending helically outwardly away from said core so that said portions define a second diameter, said portions being arranged such that adjacent portions define therebetween a helical flute;
• each of said flutes having a flute surface which is of S-shaped configuration when viewed as across section disposed normal to said longitudinal axis, said cross section being viewed in a direction from said first towards said second extremity;
• each of said portions further defining a helical bore connected to a source of a cutting fluid for permitting a flow of the cutting fluid through said bore towards said cutting point, the arrangement being such that in use of said device, the cutting fluid conveys the materials away from said cutting point through each flute;
• said first diameter having a dimension within a first range which is 20-35% of a dimension of said second diameter;
• said second extremity of the drill device being of cusp-shaped configuration for defining said cutting point;
• said drill device including:
• a first member which extends from said first extremity of said core to between said first and second extremities of said core;
• a second member fabricated from a cermet, said second member being secured to said first member, said second member extending coaxially from said first member to said cutting point;
• and
• a fastener for removably fastening said second member to said first member such that when said cutting point becomes worn, said second member is replaced.