Storage case for cutting tool

A storage case for a cutting tool, comprising:

• a bit housing to accommodate a tool bit of a cutting tool;
• a shank housing to accommodate a shank of a cutting tool;
• an extension tube having a cylindrical shape and mounted to an upper portion of the shank housing;
• and
• a sleeve which is rotatably coupled to the extension tube and to which a lower end of the bit housing is fitted, wherein
• the sleeve is provided with a plurality of concave portions and convex portions on an inner peripheral surface thereof, and the extension tube is provided with a plurality of convex portions on an outer peripheral surface thereof, such that the convex portions of the extension tube come in contact with the concave portions or the convex portions of the sleeve when the shank housing rotates,
• wherein when the convex portions of the extension tube come in contact with the convex portions of the sleeve, the sleeve is outwardly wider to thereby fix the bit housing and the extension tube of the shank housing is inwardly narrower so as to fix the shank of a cutting tool,
• wherein the extension tube is further provided with a plurality of protrusions on an inner surface at positions corresponding to the plurality of convex portions thereof, the protrusions coming in contact with the shank of a cutting tool,
• wherein the lower end of the bit housing overlaps an upper end of the shank housing.