Pencil sharpener pencil in position, although they then sharpen them to the usual conical point as for a round pencil, abandoning some distinctive aspects of the carpenter's pencil. Sharpeners with a single blade for use on wax crayons are available, and sometimes included in boxes of crayons. These often have plastic blades, which are adequate for the soft wax. Mechanical pencils dispense the graphite lead progressively during use and thus do not require sharpening; such pencils are sometimes called "self-sharpening". A type of mechanical pencil has a rotating gear mechanism which rotates the lead slightly every time the lead is lifted off
Lead of sound studios. Organ pipes are often made from a lead alloy, mixed with various amounts of tin to control the tone of each pipe. Lead is an established shielding material from radiation in nuclear science and in X-ray rooms due to its denseness and high attenuation coefficient. Molten lead has been used as a coolant for lead-cooled fast reactors. The largest use of lead in the early 21st century is in lead–acid batteries. The reactions in the battery between lead, lead dioxide, and sulfuric acid provide a reliable source of voltage. The lead in batteries undergoes no direct contact