Abstract: A cutting insert has a seating surface, an outer peripheral surface, a top surface, and an attachment hole. The cutting edge includes a curved cutting corner edge portion, a first cutting edge portion, and a second cutting edge portion. The top surface includes a first rake face contiguous to the first cutting edge portion, a second rake face contiguous to the second cutting edge portion, and a third rake face contiguous to the cutting corner edge portion and also contiguous to the first and second rake faces. The third rake face has a first region contiguous to the first rake face and a second region contiguous to the second rake face. The first rake face and the first region each have a rake angle which is a positive angle. The second rake face and the second region each have a rake angle which is a negative angle.

Abstract: A cutting insert has a seating surface, an outer peripheral surface, a top surface, and an attachment hole. The cutting edge includes a curved cutting corner edge portion, a first cutting edge portion, and a second cutting edge portion. The top surface includes a first rake face contiguous to the first cutting edge portion, a second rake face contiguous to the second cutting edge portion, and a third rake face contiguous to the cutting corner edge portion and also contiguous to the first and second rake faces. The third rake face has a first region contiguous to the first rake face and a second region contiguous to the second rake face. The first rake face and the first region each have a rake angle which is a positive angle. The second rake face and the second region each have a rake angle which is a negative angle.

Abstract: A field emission type electron microscope using a multi-stage acceleration tube wherein an acceleration voltage to be applied to at least one, always inclusive of a first-stage acceleration electrode, of acceleration electrodes is changed in interlocked relationship with a change in a field emission voltage to be applied to a field emission electrode, so that power of an electrostatic lens can be kept constant.

Abstract: Disclosed is an electromagnetic lens polepiece structure for use in an electron microscope comprising an upper polepiece and an opposite lower polepiece, each having a lens bore, wherein the lens bore portion of the upper polepiece protrudes toward the lens bore of the lower polepiece. The protrudant lens bore portion allows the provision of an X-ray conducting bore for the measurement without disturbing the magnetic field of the lens. This makes it possible a smaller lens bore and, consequently, the spherical aberration is reduced and the resolution of the microscope is improved. The protrudant lens bore structure allows the upper polepiece to be divided into two sections so that the bore section can be replaced easily for the measurement of X-rays.