Provided is a cutting insert configured to be able to realize downsizing of a cutting tool. A cutting insert includes: an upper surface and a lower surface facing each other and having a plurality of corner parts; a side surface connecting the upper surface and the lower surface and forming intersecting edges with the upper surface and the lower surface, respectively; and a through hole that has a central axis extending from the upper surface to the lower surface and that is formed for penetration from the upper surface to the lower surface. A corner cutting edge arranged at a position corresponding to a corner part of the upper surface, a minor cutting edge connected to a first end of the corner cutting edge, and a major cutting edge connected to a second end of the corner cutting edge are formed on the intersecting edge between the upper surface and the side surface. A flank of the corner cutting edge and a recessed part located on the lower surface side of the flank of the corner cutting edge are formed on the side surface.

A second distance is longer than a first distance and a value obtained by dividing the third distance by the fourth distance is more than or equal to 0.5 and less than or equal to 0.8 when it is assumed that the first distance represents a distance between the cutting edge and the mounting surface in a direction perpendicular to the rake face, the second distance represents a distance between the mounting surface and a boundary portion between the rising portion and the flat portion in the direction perpendicular to the rake face, the third distance represents a distance between the boundary portion and a tip of the cutting edge in a direction parallel to the rake face, and the fourth distance represents a distance between the second discharging opening portion and the tip of the cutting edge in the direction parallel to the rake face.

A replaceable face-milling head configured for rotating about a central rotation axis A.sub.R. The head includes a cutting portion and an integrally formed threaded shank-connector portion, the latter of which being configured for connecting to a shank. A length-diameter ratio LDR, defined as a cutting portion length L.sub.C divided by a cutting portion diameter D.sub.E, fulfills the condition: LDR1.00.

Provided is a multi-layered porous film which includes a functional layer having a controlled thickness in a length-wise direction thereof and which is suitable as a separator for batteries. The multi-layered porous film includes a base film, and a functional layer containing both an inorganic filler and a binder resin, the functional layer being formed on the base film, wherein a difference between a maximum basis weight and a minimum basis weight of the multi-layered porous film in a length-wise direction thereof is equal to or smaller than 2 grams/m.sup.2, the basis weight being measured every 100 meters interval. The separator fabricated by cutting a film roll comprised of a multi-layered porous film into pieces each having a given length has small lot-based fluctuation in quality, and makes it possible to fabricate a battery having a small fluctuation in quality.