Lead of mechanical pencils
Raw material for Spare Leads
The first was the sintering of the clay, which is the main raw material, the graphite and the binder, as well as the pencil core. However, it was not possible to obtain enough strength when the core diameter was thinned, and it was about 1.0, 1.5 mm. After that, a thin, strong core was demanded, and the method to bake the organic matter and the binding agent was discovered, and the present polymer firing core was developed. The raw material is graphite and polymer resin, but the finished core is 100% carbon because the resin is carbonized.