The beads must be very wear-resistant, so use tungsten carbide , which is second only to diamond in hardness . The tungsten carbide is first made into small particles that are slightly larger than the standard size. They are then spread on a grooved board and the small particles are fed into the circular grooves, exposing only the top. A heavy, flat top plate is then placed and pressed on top of these small particles, and grinding oil is injected between the two plates, so that the small particles are soaked in a slippery mixture containing powdered diamond. Then turn the lower plate, so that these small tungsten carbide particles keep rolling and rolling in the circular groove, constantly contacting with the groove wall, the top plate and each other, and the diamond powder constantly grinds the edges and corners of these small particles, Make them gradually round and light. During the grinding process, stop several times a day, take out these small balls, clean them, and test them until they produce small balls with moderate smoothness and meet the standard. If it is too smooth, the ink will not stick to it, and it will not be able to write. It takes about dozens of hours of intermittent grinding to produce a small ball of tungsten carbide.
Supplementary drawings:
The production of ballpoint pen tips has high requirements on the precision of processing and the selection of materials. There are not only small “balls” on the pen tip, but also five grooves to guide the ink, and the machining accuracy must reach the order of one thousandth of a millimeter.
Every small deviation will affect the writing fluency and service life of the pen tip. The thickness of the opening of the pen tip is less than 0.1 mm, and the writing angle and pressure must also be considered. , the machining error cannot exceed 0.003 mm.
