In the heart of a ballpoint pen is a precision ground metal ball which transfers fast drying, oil based ink onto paper.
The ball is usually made of mild or stainless steel, about 1/32 in (1 mm) in diameter and ground to an accuracy of a few thousandths of a millimetre. It may also be made of a tungsten and carbon compound which is almost as hard as a diamond.
Sometimes the ball is textured, or roughened, so that it can achieve a better grip on the writing service.
The ball is fitted into a steel or brass housing, designed so that it can rotate in all directions. The tip of the housing is then bent over so that the ball cannot drop out.
The ink is fired from a reservoir to the ball housing through a narrow tube. The ink reservoir must be open to the air, or have a hole in it. Otherwise, as the ink level falls a partial vacuum would be created preventing the ink from flowing.
Ridges in the metal housing distribute the ink evenly around the ball, so that when it is moved over a surface it rotates and draws a line.
The French company BiC sells more than 12 million ballpoints a day worldwide. Each pen will produce more than 2 miles (3.5 km) of writing if it has a fine point, or 1 1/2 miles (2.5 km) if it has a medium point.
Picture Credit : Google