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.
In a modern sewing machine the fabric easily glides in and out of the machine without the inconvenience of needles and thimbles and other such tools used in hand sewing, automating the process of stitching and saving time.n 1804, a sewing machine was built by the Englishmen Thomas Stone and James Henderson, and a machine for embroidering was constructed by John Duncan in Scotland. An Austrian tailor, Josef Madersperger, began developing his first sewing machine in 1807. He presented his first working machine in 1814.