To provide the tip of a ball point pen having a projected part for supporting the upper end of a spring to be housed in a bore made in the tip, its manufacturing method, and a tool suitable for use in the manufacturing method.

The spring 31 is insertingly arranged in the through hole 29 of the tip 13. The projection forming surface 47 of a caulking tool 41 forms projecting parts 35 and longitudinal grooves 37 in such a manner as to project the tank connecting part 21 of the tip 13 radially inwards under the condition that the upper end 31a of the spring 31 is pushed in downwards. The projecting parts 35 fastens the upper end 31a of the spring 31 not to come off upwards through the tank connecting part 21. By removing the caulking tool 41, the spring 31 is housed in the through hole 29 of the tip 13 under the state being compressed.