The Black Thunder coal mine in the Powder River Basin in Wyoming, US, is the fifth largest coal mine by reserve. The surface mine spread across an area of 35,700 acres was estimated to contain 1,466.1Mt of recoverable coal reserve as of December 2012. It is owned and operated by Arch Coal.
The fourth category covers modern machine tools and processes for machining ultrahard metals not machinable by older methods. 1  Machine tools that form parts by removing metal chips from a workpiece include lathes, shapers and planers, drilling machines, milling machines, grinders, and power saws.
Cold saw(ing) machines are circular saws that are used in many metal cutting operations. The saw blades used are quite large in diameter and operate at low rotational speeds, and linear feeds. There are three common types of blades used in circular saws; solid-tooth, segmental tooth, and the carbide inserted-tooth.