| 摘要 |
A magnetic disk cartridge comprises a case, a magnetic disk sheet rotatably housed in the case, and an approximately columnar center core positioned inside of the case and having a bottom surface formed as a magnetic chuck surface exposed from an aperture at the center of the case. The center core is provided with a disk sheet securing surface which faces the side opposite to the magnetic chuck surface and which is formed to a size not larger than the outer diameter of the magnetic chuck surface and further the marginal portion of which is stepped down as so not to contact the disk sheet. The magnetic disk sheet is secured to the disk sheet securing surface.
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