Abstract: The invention relates to a corner accessory for placing at the junction between at least two ducts that extend in different directions, the accessory comprising two distinct flaps, one of which includes a projecting element and the other of which includes a circular opening receiving said projecting element to allow said flaps to pivot about a pivot axis, the circular edge of said opening opening out locally to a straight slot that extends radially relative to the circular edge of said opening and that opens out into a free edge of said flap. According to the invention, said projecting element is a cylindrical wall presenting firstly an outside diameter equal, ignoring clearance, to the inside diameter of said circular opening so that during pivoting of one flap relative to the other, the outside face of said cylindrical wall slides over the edge face of the circular edge of said opening, and presenting secondly a height that varies around its circumference.

Abstract: The invention relates to a corner accessory for placing at the junction between at least two ducts that extend in different directions, the accessory comprising two distinct flaps, one of which has a projecting element and the other of which includes an elongate opening, said projecting element being engaged in said elongate opening so as to move along a longitudinal direction of said opening to allow said flaps to move relative to each other. According to the invention, said elongate opening has a longitudinal edge parallel to said longitudinal direction and opening out locally to a slot that opens out into a free edge of said flap.

Abstract: An arrangement in hand-held grinding machines intended for grinding the buttons of button drill-bits and provided with a driven spindle which carries a grinding disk. The grinding disk presents a profiled groove for shaping respective buttons of the bit to their intended tip profile. In order to enable buttons to be ground quickly and effectively with the aid of a hand-held grinding machine without needing to rotate the button to be ground about its own longitudinal axis, there is provided a spring-steel guide-spring which is mounted fixedly in relation to the grinding disk and which presents on both sides of the disk (4) obliquely and inwardly extending fingers which are intended to engage the button to be ground when the grinding disk is brought into engagement with the button.

Abstract: An abrasive wheel for grinding the cutting pins of a button-type drilling bit in a grinding machine of the kind provided with a rotatable holder for fixating the pins of the bit in a grinding position and for rotating thus fixated pins. The machine also includes a spindle on which the abrasive wheel can be mounted in a given position. The spindle/holder is linearly movable in a plane which extends through and is contained by the respective rotational axes of the holder and the spindle and in a direction parallel with the rotational axis of the spindle. The abrasive wheel includes circular flange parts which embrace a profiled groove therebetween. To enable cutting pins to be ground to an obtuse tip-profiled shape with the aid of such an abrasive wheel, the profiled groove, when seen in cross-section, is formed symmetrically around a line which intersects the rotational axis of the abrasive wheel at an angle whose complementary angle is equal to the angle of inclination of the spindle.