| 摘要 |
PROBLEM TO BE SOLVED: To eliminate defects such as a thin spot, a line discontinuity and coating irregularities and ensure and almost entirely stable ink discharging performance as a whole in terms of handwriting and a coating state by causing a tip which is a ball with a surface roughness having values such as outer diameter, arithmetic mean roughness and maximum height falling within a specific range to be held, in a rotatable manner, in the point of a writing or a coating utensil. SOLUTION: A ball formed, for example, of a tungsten carbide material which has an arithmetic mean roughness (Ra) of 0.004-0.10 μm, a surface roughness having a maximum height (Ry) having a surface roughness not exceeding 0.15 μm and an outer diameter of not more than 1.2 mm, is held, in a rotatable manner, in the point part of a tip, in which a ball holding chamber and a ball seat are formed in the tip body and thus the tip for a writing utensil or a coating utensil is formed. The point part of the tip may be of such a construction that the ball is pressed by a spring against the point edge part side of the tip directly or through a movable element without a ball seat. Further, the tip may be of such a construction that the tip body is made of pipe and the rear end of the ball is held with a bar-like material of a fiber bundle. |
