First introduced in the late 1940’s, continuous miners provided a quantum leap in the speed and efficiency of extracting coal. Modern versions operate on basically the same principal as their predecessors using a large rotating steel drum equipped with tungsten carbide steel teeth or cutting bits to cut the coal. Continuous mining currently accounts for about 49% of total U.S. underground coal production each year. Standard continuous miners can extract coal at a rate of up to 38 tons a minute depending upon the seam thickness. In underground mining, first and foremost in the modernization process are the machines that extract coal: primarily the continuous and longwall miners.