Cutting insert, cutting tool, and method for manufacturing machined product
A cutting insert has an upper surface, a lower surface and a lateral surface. The upper surface has a first upper side, and a second upper side. The lower surface has a first lower side and a second lower side. The lateral surface has a first lateral surface, a second lateral surface, and a third lateral surface. The first lateral surface has a first concave part having a first constraining surface having a flat shape. The second lateral surface has a second concave part having a second constraining surface having a flat shape. The third lateral surface has a convex part. The first concave part and the second concave part are separated from each other by the convex part.
1. A cutting insert, comprising:
an upper surface having a polygonal shape, the upper surface comprising
a first upper corner,
a first upper side extended from the first upper corner, and
a second upper side extended from the first upper corner;
a lower surface having a polygonal shape, the lower surface comprising
a first lower corner located below the first upper corner,
a first lower side located below the second upper side and extended from the first lower corner, and
a second lower side located below the first upper side and extended from the first lower corner;
a lateral surface located between the upper surface and the lower surface;
an upper cutting edge located on an intersection of the upper surface and the lateral surface; and
a lower cutting edge located on an intersection of the lower surface and the lateral surface,
wherein
the lateral surface comprises
a first lateral surface connecting to the first upper side and the second lower side,
a second lateral surface connecting to the second upper side and the first lower side, and
a third lateral surface located between the first lateral surface and the second lateral surface,
an imaginary straight line passing through a center of the upper surface and a center of the lower surface is a central axis,
the first lateral surface comprises a first concave part comprising
a first constraining surface having a flat shape, and
a first inclined surface closer to the first upper side than the first constraining surface, the first inclined surface extending away from a first virtual straight line as the first inclined surface extending towards the first upper side, the first virtual straight line passing through the first upper side and parallel to the central axis,
the second lateral surface comprises a second concave part comprising a second constraining surface having a flat shape,
the third lateral surface comprises a convex part having a convex shape in a cross section along the central axis,
the first concave part and the second concave part are separated from each other by the convex part,
the first constraining surface is located halfway between the upper surface and the lower surface in a direction along the central axis, and
in a cross section orthogonal to the first upper side,
a first point at the first constraining surface is located closer to the first virtual straight line than a second point at the first constraining surface, the first point at the first constraining surface being located between the first upper side and the second point at the first constraining surface in the direction along the central axis,
an end point of the first constraining surface on a side of the lower surface is located on an outer side of the first virtual straight line, and
a first point at the first inclined surface is located further away from the first virtual straight line than a second point at the first inclined surface, the first point at the first inclined surface being located between the first upper side and the second point at the first inclined surface in the direction along the central axis.
2. The cutting insert according to claim 1 , wherein
an imaginary plane that is orthogonal to the central axis and is located halfway between the upper surface and the lower surface is a reference plane, and
the first constraining surface and the second constraining surface individually intersect with the reference plane.
3. The cutting insert according to claim 1 , wherein
the upper cutting edge comprises
an upper major cutting edge located on the first upper side, and
an upper minor cutting edge located on the second upper side, and
the second point at the first constraining surface is located further away from the central axis than the first point at the first constraining surface, the second point at the first constraining surface is between the second lower side and the first point at the first constraining surface in the direction along the central axis.
4. The cutting insert according to claim 1 , wherein
the lower cutting edge comprises
a lower major cutting edge located on the first lower side, and
a lower minor cutting edge located on the second lower side, and
a third point at the second constraining surface is located further away from the central axis than a fourth point at the second constraining surface, the third point at the second constraining surface is between the second upper side and the fourth point at the second constraining surface in the direction along the central axis.
5. The cutting insert according to claim 1 , wherein
the lower surface comprises a lower seating surface having a flat shape, and
the second lower side is located further away from the central axis than the first upper side in a radial direction perpendicular to the direction along the central axis.
6. The cutting insert according to claim 1 , wherein
the first concave part comprises
a first bottom part,
a first upper opening located on a side of the upper surface, and
a first lower opening located on a side of the lower surface, and
in a cross section orthogonal to the first upper side, a distance from the first bottom part to the first upper opening in a radial direction perpendicular to the direction along the central axis is smaller than a distance from the first bottom part to the first lower opening in the radial direction.
7. The cutting insert according to claim 1 , wherein
the upper surface comprises an upper seating surface having a flat shape, and
the second upper side is located further away from the central axis than the first lower side in a radial direction perpendicular to the direction along the central axis.
8. The cutting insert according to claim 1 , wherein
the second concave part comprises
a second bottom part,
a second upper opening located on a side of the upper surface, and
a second lower opening located on a side of the lower surface, and
in a cross section orthogonal to the first lower side, a distance from the second bottom part to the second lower opening in a radial direction perpendicular to the direction along the central axis is smaller than a distance from the second bottom part to the second upper opening in the radial direction.
9. A cutting tool, comprising:
a holder having a columnar shape extended along a rotation axis from a first end to a second end, the holder comprising a pocket located on a side of the first end; and
the cutting insert according to claim 1 , the cutting insert being located in the pocket.
10. A method for manufacturing a machined product, the method comprising:
rotating the cutting tool according to claim 9 ;
bringing the cutting tool being rotated into contact with a workpiece; and
moving the cutting tool away from the workpiece.
11. The cutting insert according to claim 1 , wherein
the second concave part further comprises a second inclined surface closer to the first lower side than the second constraining surface, the second inclined surface extending away from a second virtual straight line as the second inclined surface extending towards the first lower side, the second virtual straight line passing through the first lower side and parallel to the central axis,
the second constraining surface is located halfway between the upper surface and the lower surface in the direction along the central axis, and
in a cross section orthogonal to the first lower side,
a first point at the second constraining surface is located further away from a second virtual straight line than a second point at the second constraining surface, the first point at the second constraining surface being located between the second upper side and the second point at the second constraining surface in the direction along the central axis,
an end point of the second constraining surface on a side of the upper surface is located on an outer side of the second virtual straight line, and
a first point at the second inclined surface is located further away from the second virtual straight line than a second point at the second inclined surface, the second point at the second inclined surface being located between the second upper side and the first point at the second inclined surface in the direction along the central axis.