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A sawmill is a facility where logs are cut into lumber. ==Sawmill process== A sawmill's basic operation is much like those of hundreds of years ago; a log enters on one end and dimensional lumber exits on the other end. *After trees are selected for harvest, the next step in logging is felling the trees, and bucking them to length. *Branches are cut off the trunk. This is known as ''limbing''. *Logs are taken by logging truck, rail or a log drive to the sawmill. *Logs are scaled either on the way to the mill or upon arrival at the mill. *Debarking removes bark from the logs. *''Decking'' is the process for sorting the logs by species, size and end use (lumber, plywood, chips). *A sawyer uses a head saw, head rig or primary saw to break the log into cants (unfinished logs to be further processed) and flitches (unfinished planks). *Depending upon the species and quality of the log, the cants will either be further broken down by a resaw or a gang edger into multiple flitches and/or boards *''Edging'' will take the flitch and trim off all irregular edges leaving four-sided lumber. *''Trimming'' squares the ends at typical lumber lengths. *''Drying'' removes naturally occurring moisture from the lumber. This can be done with kilns or air-dried. *''Planing'' smooths the surface of the lumber leaving a uniform width and thickness. *''Shipping'' transports the finished lumber to market.〔 〕 ==Early history== The Hierapolis sawmill, a Roman water-powered stone saw mill at Hierapolis, Asia Minor (modern-day Turkey) dating to the second half of the 3rd century AD is the earliest known sawmill. It is also the earliest known machine to incorporate a crank and connecting rod mechanism. Water-powered stone sawmills working with cranks and connecting rods, but without gear train, are archaeologically attested for the 6th century AD at the Eastern Roman cities Gerasa and Ephesus. The earliest literary reference to a working sawmill comes from a Roman poet, Ausonius who wrote an epic poem about the river Moselle in Germany in the late 4th century AD. At one point in the poem he describes the shrieking sound of a watermill cutting marble. Marble sawmills also seem to be indicated by the Christian saint Gregory of Nyssa from Anatolia around 370/390 AD, demonstrating a diversified use of water-power in many parts of the Roman Empire.〔 Sawmills became widespread in medieval Europe again, as one was sketched by Villard de Honnecourt in c. 1250.〔C. Singer ''et at.'', ''History of Technology'' II (Oxford 1956), 643-4.〕 They are claimed to have been introduced to Madeira following its discovery in c. 1420 and spread widely in Europe in the 16th century.〔Charles E. Peterson, 'Sawdust Trail: Annals of Sawmilling and the Lumber Trade' ''Bulletin of the Association for Preservation Technology'' Vol. 5, No. 2. (1973), pp. 84-5.〕 By the 11th century, hydropowered sawmills were in widespread use in the medieval Islamic world, from Islamic Spain and North Africa in the west to Central Asia in the east.〔Adam Robert Lucas (2005), "Industrial Milling in the Ancient and Medieval Worlds: A Survey of the Evidence for an Industrial Revolution in Medieval Europe", ''Technology and Culture'' 46 (1): 1-30 ()〕 Prior to the invention of the sawmill, boards were rived (split) and planed, or more often sawn by two men with a whipsaw, using saddleblocks to hold the log, and a saw pit for the pitman who worked below. Sawing was slow, and required strong and hearty men. The topsawer had to be the stronger of the two because the saw was pulled in turn by each man, and the lower had the advantage of gravity. The topsawyer also had to guide the saw so that the board was of even thickness. This was often done by following a chalkline. Early sawmills simply adapted the whipsaw to mechanical power, generally driven by a water wheel to speed up the process. The circular motion of the wheel was changed to back-and-forth motion of the saw blade by a connecting rod known as a ''pitman arm'' (thus introducing a term used in many mechanical applications). Generally, only the saw was powered, and the logs had to be loaded and moved by hand. An early improvement was the development of a movable carriage, also water powered, to move the log steadily through the saw blade. A type of sawmill without a crank is known from Germany called "knock and drop" or simply "drop" -mills. In these drop sawmills, the frame carrying the saw blade is knocked upwards by cams as the shaft turns. These cams are let into the shaft on which the waterwheel sits. When the frame carrying the saw blade is in the topmost position it drops by its own weight, making a loud knocking noise, and in so doing it cuts the trunk.” 〔http://www.familienverband-tritschler.de/index.php?id=81&L=1〕 A small mill such as this would be the center of many rural communities in wood-exporting regions such as the Baltic countries and Canada. The output of such mills would be quite low, perhaps only 500 boards per day. They would also generally only operate during the winter, the peak logging season. In the United States, the sawmill was introduced soon after the colonisation of Virginia by recruiting skilled men from Hamburg. Later the metal parts were obtained from the Netherlands,〔Peterson, 94-5.〕 where the technology was far ahead of that in England, where the sawmill remained largely unknown until the late 18th century. The arrival of a sawmill was a large and stimulative step in the growth of a frontier community. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「sawmill」の詳細全文を読む スポンサード リンク
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