Cutting holder and cutting tool

A cutting holder comprising:

• a columnar holder main body that has, at one end in a longitudinal-direction, an insert seating surface on which a cutting insert is capable of being mounted, and that is formed with a through-hole which is open, on one side, toward the insert seating surface and is open, on the other side, toward the other end on a side opposite to the one end;
• a clamp for insert having a clamping portion that presses the cutting insert against the insert seating surface, and a first screw portion connected to the clamping portion;
• and
• a screw having a second screw portion that is screwed to the first screw portion,
• wherein the through-hole has a small inner diameter portion having an inner diameter smaller than an outer diameter of the screw,
• the clamping portion of the clamp for insert is disposed on cutting edge side with respect to an end on the other end side of the small inner diameter portion,
• the screw is disposed on the other end side with respect to the small inner diameter portion,
• a screw portion that is a male screw, out of the first screw portion and the second screw portion, is screwed to a screw portion that is a female screw, out of the first screw portion and the second screw portion, on a deep side with respect to the end on the other end side of the small inner diameter portion when viewed from a root of the male screw,
• the screw rotates, so that the clamp for insert moves along a rotation axis of the screw, and
• the clamp for insert moves toward the other end side, so that the clamping portion presses the cutting insert against the insert seating surface.