Reamer core drill with cutting bits

In a reamer-core drill having a longitudinal axis, a diameter which can be fine-set relative to said longitudinal axis, a clamping zone and a shank,

• said shank having an outer side and a front end zone, two cutting bits, each having a core cutting edge zone, fastened in opposite directions in said front end zone, and a chip space in front of each of said cutting bits,
• the improvement wherein,
• said shank has a longitudinal slot oriented radially with respect to said geometrical longitudinal axis which divides said shank into shank halves, said longitudinal slot having one end which opens at said front end zone and an opposite end which extends inwards into said shank towards said clamping zone a distance adequate to enable said shank halves to bend at said front end zone to a degree adequate to permit fine setting of said diameter of said core-reamer drill,
• each of said shank halves has a first shank half portion and a second shank half portion having a cross section that is substantially smaller than said first half portion,
• each of said first shank half portions has one of said two cutting bits secured thereto and lays behind and at about the same level as said cutting bit,
• each of said second shank half portions lays between one of said chip spaces and said longitudinal slot,
• coaxial with said longitudinal axis, said shank has a tapped hole that extends at one end further inwards into said shank towards said clamping zone than said longitudinal slot, and a rest hole that extends at one end outwards towards said front end zone,
• a first screw has a screw shank with a first screw shank portion engaged in said tapped hole, a second screw shank portion passing through said rest hole, and a screw head with a slightly conical circumferential surface which tapers toward said screw shank coaxially with said longitudinal axis,
• said shank has a tapered hole at said outward end of said rest hole which is complementary with said circumferential surface of said screw head into which said screw head can be inserted to expand said longitudinal slot and widen said diameter of said reamer-core drill,
• second and third screws pass transversely through said longitudinal slot on each side of said geometrical longitudinal axis substantially closer to said open end than said inward end of said longitudinal slot, which narrows said longitudinal slot when said second and third screws are tightened, and
• said shank has said two cutting bits arranged thereon with said cutting edges of said cutting bits disposed rotationally coincident at said outer side of said shank.