Abstract: A scribing head 1 of this invention raises and lowers a scribing cutter by rotation of a servomotor 3. As a scribe pressure, a rotational torque of the servomotor 3 is transmitted to the scribing cutter. To form a scribe line across another scribe line which is formed earlier, the scribe pressure is raised temporarily when the scribing head passes the scribe line which is formed earlier. The rotational torque of the servomotor 3 is controlled at any of preset limits while the position of a cutter 6 of the scribing head shifts on the brittle substrate. The servomotor 3 is driven under position-control mode.

Abstract: A cutter wheel for brittle materials includes a disk with two side planes and an outer peripheral portion between the planes. The outer peripheral portion includes two bevel portions and a ridge portion between the bevel portions. The ridge portion has a plurality of peaks aligned along a circumferential line. For example, the ridge portion includes a straight line connecting two adjacent peaks in the plurality of peaks. Alternatively, the ridge portion is a depression between two adjacent peaks in the plurality of peaks, and the depth of the depression is deeper than the straight line connecting the two adjacent peaks. Preferably, the peaks are spaced apart at an equal distance.

Abstract: A cutter wheel for forming scribe lines on a brittle plate has a disk with two side planes. The disk has an edge formed at the outer periphery of the disk and a shaft hole formed at the center of the disk for inserting a rotational shaft. Further, at least one groove is formed to extend from a surface of one of the side planes along the shaft hole.

Abstract: When lines of vertical cracks due to thermal strain are formed for a plate made of a brittle material with a laser, the plate is irradiated with a laser beam along first lines in a first direction, and thereafter along second lines in a second direction crossing the first direction. When the second lines are scribed, depths of the generated vertical cracks are controlled to be shallower than those of the vertical cracks generated along the first lines in the first direction. The scribing is controlled by setting irradiation energy of the laser beam per unit area and per unit time in the second direction to be lower than that in the first direction. For example, moving speed of the laser spot relative to the plate is varied or output power of the laser beam is controlled on the irradiation energy.

Abstract: A glass cutting disc forms a scribed line on a surface of a glass product along which the glass product can be broken when an external force is applied thereto. The glass cutting disc includes an outer peripheral portion radially outwardly beveled to define a peripheral ridge. The peripheral ridge has surface features formed thereon so as to alternate in a direction circumferentially of the cutting disc. The surface features may be in the form of protrusions and grooves that alternate with each other over the peripheral ridge.