Mechanical pencil Mechanical pencil A mechanical pencil (US English) or propelling pencil (UK English), also clutch pencil, is a pencil with a replaceable and mechanically extendable solid pigment core called a "lead" . The lead, often made of graphite, is not bonded to the outer casing, and can be mechanically extended as its point is worn away. Other names include microtip pencil, automatic pencil, drafting pencil, technical pencil, click pencil, pump pen, pump pencil, leadholder, pen pencil (Indian English), and lead pencil (Bangladeshi and American English). Mechanical pencils are used to provide lines of constant width without sharpening in technical drawing and
Lead smelting methods are usually used to remove the remaining non-lead components of the mixture, for example the Betterton-Kroll process and the Betts electrolytic process. The non-lead metals are usually sold to other metal processing plants. The refined lead may be made into alloys or directly cast. People who operate or work in such plants are also referred to as smelters. Galena, the most common mineral of lead, is primarily lead sulfide (PbS). The sulfide is oxidized to a sulfite (PbSO) which thermally decomposes into lead oxide and sulfur dioxide gas. (PbO and SO) The sulfur dioxide (like the carbon dioxide in