A writing instrument configured to apply a writing material or liquid to a surface, comprising a socket, and a ball arranged in the socket, characterized by at least one first component which is arranged to come into contact with the ball, wherein the at least one first component comprises a first material having surface properties such that the friction coefficient between the ball and the at least one first component decreases when the force acting from the ball on the at least one first component increases at least within a certain range of forces.

A metallic ball pen tip for a writing instrument comprising a feeding passage extending in an axial direction, the feeding passage reaching in a recess configured to receive a ball, the recess being defined by a cylindrical wall and a ball seat, wherein the ball seat comprises a plurality of feeding grooves and wherein the ball seat is textured, the texture comprising a plurality of blind holes having a depth equal to or smaller than 50 μm, preferably equal to or smaller than 10 μm, more preferably equal to or smaller than 5 μm, more preferably equal to or smaller than 1 μm, the blind holes having a total surface equal to or greater than 20% of the ball seat, preferably 60% and equal to or smaller than 90% of the ball seat, preferably 85%. A method of manufacturing a metallic ball pen tip.

A method of manufacturing a metallic ball pen tip for a writing instrument comprising a feeding passage extending in an axial direction, the feeding passage reaching in a housing configured to receive a ball, the housing being defined by a cylindrical wall and a wall, the method comprising the steps providing a preform of the metallic ball pen tip comprising the feeding passage and the housing, the housing being defined by the cylindrical wall and a wall, machining the wall so as to obtain a stepped wall, broaching feeding grooves in the stepped wall and coining the stepped wall with a spherical die so as to obtain the ball seat, and a metallic ball pen tip obtained by the method.

A metallic ball pen tip for a writing instrument comprising a feeding passage extending in an axial direction, the feeding passage reaching in a recess configured to receive a ball, the recess being defined by a cylindrical wall and a ball seat, wherein the ball seat comprises a plurality of feeding grooves and wherein the ball seat is textured, the texture comprising a plurality of blind holes having a depth equal to or smaller than 50 μm, preferably equal to or smaller than 10 μm, more preferably equal to or smaller than 5 μm, more preferably equal to or smaller than 1 μm, the blind holes having a total surface equal to or greater than 20% of the ball seat, preferably 60% and equal to or smaller than 90% of the ball seat, preferably 85%. A method of manufacturing a metallic ball pen tip.

A ballpoint pen tip comprises: a ball having a diameter of 0.5 mm or less; and a tip body, wherein the tip body has a ball holding chamber, a rear hole, an ink flow hole, and an ink flow groove opening to the ball holding chamber, and not reaching the rear hole. A ratio of an ink consumption per 100 m of handwriting to a diameter of the ball is 200 mg/mm or more and 800 mg/mm or less, and when a front end of the ink flow groove is set as a start point and a position of 0.3 mm rearward from the front end of the ink flow hole is set as an end point, a volume of a first space in the ink flow hole and the ink flow groove from the start point to the end point is 0.02 mm.sup.3 or more.

A ballpoint pen tip comprises: a ball having a diameter of 0.5 mm or less; and a tip body, wherein the tip body has a ball holding chamber, a rear hole, an ink flow hole, and an ink flow groove opening to the ball holding chamber, and not reaching the rear hole. A ratio of an ink consumption per 100 m of handwriting to a diameter of the ball is 200 mg/mm or more and 800 mg/mm or less, and when a front end of the ink flow groove is set as a start point and a position of 0.3 mm rearward from the front end of the ink flow hole is set as an end point, a volume of a first space in the ink flow hole and the ink flow groove from the start point to the end point is 0.02 mm.sup.3 or more.

A method of manufacturing a metallic ball pen tip for a writing instrument comprising a feeding passage extending in an axial direction, the feeding passage reaching in a housing configured to receive a ball, the housing being defined by a cylindrical wall and a wall, the method comprising the steps providing a preform of the metallic ball pen tip comprising the feeding passage and the housing, the housing being defined by the cylindrical wall and a wall, machining the wall so as to obtain a stepped wall, broaching feeding grooves in the stepped wall and coining the stepped wall with a spherical die so as to obtain the ball seat, and a metallic ball pen tip obtained by the method.

A writing instrument configured to apply a writing material or liquid to a surface, comprising a socket, and a ball arranged in the socket, characterized by at least one first component which is arranged to come into contact with the ball, wherein the at least one first component comprises a first material having surface properties such that the friction coefficient between the ball and the at least one first component decreases when the force acting from the ball on the at least one first component increases at least within a certain range of forces.

To make it possible to easily change a writing line width. A ballpoint pen chip that brings a front half part side of a transfer ball into contact with an inward annular protrusion on a front end side in a chip body from a backward side of the inward annular protrusion and receives a rear half part side of the transfer ball with a front end part of a receiving member. The receiving member includes, on a front end side thereof, a reduction part gradually reduced in a cross-sectional area forward. A front-most end part of the reduction part is disposed backward from the transfer ball. A portion of the receiving member further on a rear side than the reduction part is unretreatably fixed to the chip body and configured to elastically contract when a pressing force is received from the transfer ball.

Embodiments of the invention are directed to a roller ball marking instrument for use with paint, a method for assembling the roller ball marking instrument, and a system for delivering paint. The body of the marking instrument includes a reservoir for storing paint. The body is coupled to a fibrous roller ball via a retaining ring. The roller balls sits within a partially-enclosed cavity in the center of the retaining ring. A least part of the roller ball protrudes through an opening in the retaining ring. Paint in the reservoir moves first through an opening at one end of the body and then through an open center of the retaining ring. The paint is transferred to the roller ball. The roller ball rotates freely within the cavity of the retaining ring and transfers the paint to a writing surface.