LARGE DIAMETER BORE DRILL (VERSIONS) Russian patent published in 2012 - IPC B23B51/04 

FIELD: process engineering.

SUBSTANCE: drill consists of shank and working part made up of three sheets coiled to form hollow helical surface with chips removal flutes. Said sheets feature trapezoid shape and are coiled in lengthwise direction relative to proper axis of symmetry and bent in crosswise direction on tapered mandrel. Said sheets are jointed together to form hollow helical cavity along working length. Said working part is provided with conical screw lines made on its outer surface and conical helical lines on its inner surface, all over its length. Cutting and reaming edges are made on face side of larger-diameter working part in different planes. Note here that chamfer of 5-30° is made on every trapezoid sheet base. In compliance with another version, working part is made up of three and more helical trapezoid sheets of curvilinear convex or concave shape circumscribed by curves varying in order and degree of curvature with centers located inside and outside working part cross-section.

EFFECT: expanded operating performances.

2 cl, 9 dwg