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.

An oil-based ballpoint pen includes: a ballpoint pen tip at a tip part of an ink storage cylinder, and an oil-based ballpoint pen ink composition stored in the ink storage cylinder, the oil-based ballpoint pen ink composition containing a colorant, an organic solvent having a boiling point of 140? C. or lower, and a resin, wherein the oil-based ballpoint pen ink composition has an ink viscosity of 300 mPa.Math.s or less at 20? C. and a shear rate of 200 sec.sup.?1, an ink consumption of the oil-based ballpoint pen per a writing distance of 100 m is 80 mg or more, and a ratio of a ball diameter B (mm) to an ink consumption A (mg) per a writing distance of 100 m satisfies 100<A/B<600.

An oil-based ballpoint pen includes: a ballpoint pen tip at a tip part of an ink storage cylinder, and an oil-based ballpoint pen ink composition stored in the ink storage cylinder, the oil-based ballpoint pen ink composition containing a colorant, an organic solvent having a boiling point of 140? C. or lower, and a resin, wherein the oil-based ballpoint pen ink composition has an ink viscosity of 300 mPa.Math.s or less at 20? C. and a shear rate of 200 sec.sup.?1, an ink consumption of the oil-based ballpoint pen per a writing distance of 100 m is 80 mg or more, and a ratio of a ball diameter B (mm) to an ink consumption A (mg) per a writing distance of 100 m satisfies 100<A/B<600.

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 writing instrument excellent in handwriting density and temporal stability. The writing instrument includes a ball-point pen tip attached to the front end portion of the ink storage cylinder; and a ball-point pen refill having an ink composition for a writing instrument loaded therein. The ink composition for the writing instrument is a thermochromic ink containing at least a thermochromic microcapsule pigment. The writing instrument includes a pressurization mechanism for applying a pressure to the back end of the ink composition for the writing instrument.

A writing instrument excellent in handwriting density and temporal stability. The writing instrument includes a ball-point pen tip attached to the front end portion of the ink storage cylinder; and a ball-point pen refill having an ink composition for a writing instrument loaded therein. The ink composition for the writing instrument is a thermochromic ink containing at least a thermochromic microcapsule pigment. The writing instrument includes a pressurization mechanism for applying a pressure to the back end of the ink composition for the writing instrument.

A writing instrument assembly has a writing instrument with a body and a working tip extended or extendable from the body. A holder has a landing spot for the writing instrument. The writing instrument is magnetically and detachably retained at the landing spot when attached to the holder. The working tip is sheathed or covered automatically when the writing instrument is attached to the holder and is unsheathed or uncovered when detached from the holder.

A writing instrument assembly has a writing instrument with a body and a working tip extended or extendable from the body. A holder has a landing spot for the writing instrument. The writing instrument is magnetically and detachably retained at the landing spot when attached to the holder. The working tip is sheathed or covered automatically when the writing instrument is attached to the holder and is unsheathed or uncovered when detached from the holder.

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.