Abstract: A disk-shaped glass substrate for a magnetic-disk glass substrate includes an outer circumference having a roundness of 1.3 ?m or less. A first reference circle is obtained with a least squares method from a first outline corresponding to a shape of a lap around the outer circumference. A second reference circle is obtained with a least squares method from a second outline obtained by performing low-pass filtering using a period in which the number of peaks per lap is 150 as a cut-off value on the first outline. A ratio of the second peak count value defined by the number of peaks of the second outline that project outward in a radial direction from the second reference circle to the first peak count value defined by the number of peaks of the first outline that project outward in a radial direction from the first reference circle is 0.2 or less.

Abstract: A disk-shaped glass substrate for a magnetic-disk glass substrate includes an outer circumference having a roundness of 1.3 ?m or less. A first reference circle is obtained with a least squares method from a first outline corresponding to a shape of a lap around the outer circumference. A second reference circle is obtained with a least squares method from a second outline obtained by performing low-pass filtering using a period in which the number of peaks per lap is 150 as a cut-off value on the first outline. A ratio of the second peak count value defined by the number of peaks of the second outline that project outward in a radial direction from the second reference circle to the first peak count value defined by the number of peaks of the first outline that project outward in a radial direction from the first reference circle is 0.2 or less.

Abstract: The invention aims at providing a method for manufacturing a glass substrate for a magnetic disc capable of eliminating undulations of an outer peripheral end face of a glass substrate in a short processing time, and obtaining high roundness. In a method for manufacturing a disc-like glass substrate for a magnetic disc, the method includes a forming step of pressing a rotating grindstone against an outer peripheral end face while the glass substrate is rotated, thereby forming an outer peripheral end. In the forming step, processing is performed using a first condition (S106) on which first undulations are formed and a second condition (S108) on which second undulations having a different wavelength from the first undulations are formed.

Abstract: The invention aims at providing a method for manufacturing a glass substrate for a magnetic disc capable of eliminating undulations of an outer peripheral end face of a glass substrate in a short processing time, and obtaining high roundness. In a method for manufacturing a disc-like glass substrate for a magnetic disc, the method includes a forming step of pressing a rotating grindstone against an outer peripheral end face while the glass substrate is rotated, thereby forming an outer peripheral end. In the forming step, processing is performed using a first condition (S106) on which first undulations are formed and a second condition (S108) on which second undulations having a different wavelength from the first undulations are formed.

Abstract: A magnetic polishing method capable of easily and satisfactorily polishing the inner peripheral end face of a circular hole (1) at the center part of a disk substrate (2) even if the diameter of the circular hole is reduced. By this method, a large quantity of disk substrates with stable quality can be supplied, thermal asperity trouble and head crush can be prevented from occurring on a magnetic disk, and the density of the information recording surface of the magnetic disk can be increased.

Abstract: A magnetic polishing method capable of easily and satisfactorily polishing the inner peripheral end face of a circular hole (1) at the center part of a disk substrate (2) even if the diameter of the circular hole is reduced. By this method, a large quantity of disk substrates with stable quality can be supplied, thermal asperity trouble and head crush can be prevented from occurring on a magnetic disk, and the density of the information recording surface of the magnetic disk can be increased.