Asawmill (saw mill,saw-mill) orlumber mill is a facility wherelogs are cut intolumber. Modern sawmills use a motorized saw to cut logs lengthwise to make long pieces, and crosswise to length depending on standard or custom sizes (dimensional lumber). The"portable" sawmill is simple to operate. The log lies flat on a steel bed, and the motorized saw cuts the log horizontally along the length of the bed, by the operator manually pushing the saw. The most basic kind of sawmill consists of achainsaw and a customized jig ("Alaskan sawmill"), with similar horizontal operation.
Before the invention of the sawmill, boards were made in variousmanual ways, eitherrived (split) andplaned,hewn, or more oftenhand sawn by two men with awhipsaw, one above and another in asaw pit below. The earliest known mechanical mill is theHierapolis sawmill, a Roman water-powered stone mill atHierapolis,Asia Minor dating back to the 3rd century AD. Other water-powered mills followed and by the 11th century they were widespread in Spain and North Africa, the Middle East and Central Asia, and in the next few centuries, spread across Europe. The circular motion of the wheel was converted to a reciprocating motion at the saw blade. 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.
By the time of theIndustrial Revolution in the 18th century, the circular saw blade had been invented, and with the development of steam power in the 19th century, a much greater degree of mechanisation was possible. Scrap lumber from the mill provided a source of fuel for firing the boiler. The arrival of railroads meant that logs could be transported to mills rather than mills being built beside navigable waterways. By 1900, the largest sawmill in the world was operated by theAtlantic Coast Lumber Company in Georgetown, South Carolina, using logs floated down thePee Dee River from theAppalachian Mountains. In the 20th century the introduction of electricity and high technology furthered this process, and now most sawmills are massive andexpensive facilities in which most aspects of the work are computerized. Besides the sawn timber, use is made of all the by-products includingsawdust,bark,woodchips, andwood pellets, creating a diverse offering offorest products.
A sawmill's basic operation is much like those of hundreds of years ago: a log enters on one end anddimensional lumber exits on the other end.
TheHierapolis sawmill, awater-powered stone sawmill atHierapolis,Asia Minor (modern-dayTurkey, then part of theRoman Empire), dating to the second half of the 3rd century, is the earliest known sawmill. It also incorporates acrank andconnecting rod mechanism.[2]
Water-powered stone sawmills working with cranks and connecting rods, but withoutgear train, are archaeologically attested for the 6th century at theByzantine citiesGerasa (in Asia Minor) andEphesus (inSyria).[3]
The earliest literary reference to a working sawmill comes from aRoman poet,Ausonius, who wrote atopographical poem about the riverMoselle inGermany in the late 4th century AD. At one point in the poem, he describes the shrieking sound of a watermill cuttingmarble.[4] Marble sawmills also seem to be indicated by theChristian saintGregory of Nyssa fromAnatolia around 370–390 AD, demonstrating a diversified use of water-power in many parts of theRoman Empire.[4]
Sawmills later became widespread inmedieval Europe, as one was sketched byVillard de Honnecourt in c. 1225–1235.[5] They are claimed to have been introduced toMadeira following its discovery in c. 1420 and spread widely in Europe in the 16th century.[6]: 84–85
Prior to the invention of the sawmill, boards wererived (split) and planed, or more often sawn by two men with awhipsaw, using saddleblocks to hold the log, and asaw 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 thewhipsaw to mechanical power, generally driven by awater wheel to speed up the process. The circular motion of the wheel was changed to back-and-forth motion of the saw blade by aconnecting rod known as apitman 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.[7]
A small mill such as this would be the center of many rural communities in wood-exporting regions such as theBaltic countries andCanada. 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 theUnited States, the sawmill was introduced soon after the colonisation ofVirginia by recruiting skilled men fromHamburg.Later the metal parts were obtained from the Netherlands,[6]: 94–95 where the technology was far ahead of that inEngland, 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.
TheDutchwindmill ownerCornelis Corneliszoon van Uitgeest invented in 1594 the wind-powered sawmill, which made the conversion of log timber into planks 30 times faster than before.[8] His wind-powered sawmill used acrankshaft to convert awindmill's circular motion into a back-and-forward motion powering the saw, and was granted a patent for the technique.[9]
Early mills had been taken to the forest, where a temporary shelter was built, and the logs were skidded to the nearby mill by horse or ox teams, often when there was some snow to provide lubrication. As mills grew larger, they were usually established in more permanent facilities on a river, and the logs were floated down to them bylog drivers. Sawmills built on navigable rivers, lakes, or estuaries were called cargo mills because of the availability of ships transporting cargoes of logs to the sawmill and cargoes of lumber from the sawmill.[10]
The next improvement was the use of circular saw blades, perhaps invented in England in the late 18th century, but perhaps in 17th-century Netherlands. Soon thereafter, millers used gangsaws, which added additional blades so that a log would be reduced to boards in one quick step. Circular saw blades were extremely expensive and highly subject to damage by overheating or dirty logs. A new kind of technician arose, thesawfiler. Sawfilers were highly skilled in metalworking. Their main job was toset and sharpen teeth. The craft also involved learning how tohammer a saw, whereby a saw is deformed with a hammer and anvil to counteract the forces of heat and cutting. Moderncircular saw blades have replaceable teeth, but still need to be hammered.[11]
The introduction ofsteam power in the 19th century created many new possibilities for mills. Availability of railroad transportation for logs and lumber encouraged building of rail mills away from navigable water. Steam powered sawmills could be far more mechanized. Scrap lumber from the mill provided a ready fuel source for firing the boiler. Efficiency was increased, but the capital cost of a new mill increased dramatically as well.[10]
In addition, the use of steam or gasoline-poweredtraction engines also allowed the entire sawmill to be mobile.[12][13]
By 1900, the largest sawmill in the world was operated by the Atlantic Lumber Company inGeorgetown, South Carolina, using logs floated down thePee Dee River from as far as the edge of theAppalachian Mountains inNorth Carolina.
A restoration project for Sturgeon's Mill in Northern California is underway, restoring one of the last steam-powered lumber mills still using its original equipment.
In the twentieth century the introduction of electricity and high technology furthered this process, and now most sawmills are massive and expensive facilities in which most aspects of the work iscomputerized. The cost of a new facility with 4,700-cubic-metre-per-day (2-million-board-foot-per-day) capacity is up toCAN$120,000,000. A modern operation will produce between 240,000 to 1,650,000 cubic metres (100 to 700 million board feet) annually.
Small gasoline-powered sawmills run by local entrepreneurs served many communities in the early twentieth century, and specialty markets still today.
A trend is the smallportable sawmill for personal or even professional use. Many different models have emerged with different designs and functions. They are especially suitable for producing limited volumes of boards, or specialty milling such as oversized timber. Portable sawmills have gained popularity for the convenience of bringing the sawmill to the logs and milling lumber in remote locations.[14] Some remote communities that have experienced natural disasters have used portable sawmills to rebuild their communities out of the fallen trees.
Technology has changed sawmill operations significantly in recent years, emphasizing increasing profits through waste minimization and increased energy efficiency as well as improving operator safety. The once-ubiquitous rusty, steelconicalsawdust burners have for the most part vanished, as the sawdust and other mill waste is now processed intoparticleboard and related products, or used to heatwood-drying kilns. Co-generation facilities will produce power for the operation and may also feed superfluous energy onto the grid. While the bark may be ground for landscapingbarkdust, it may also be burned for heat. Sawdust may make particle board or be pressed intowood pellets for pellet stoves. The larger pieces of wood that will not make lumber are chipped into wood chips and provide a source of supply for paper mills. Wood by-products of the mills will also makeoriented strand board (OSB) paneling for building construction, a cheaper and in some use cases more robust alternative to plywood for paneling. Some automatic mills can process 800 small logs into bark chips, wood chips, sawdust and sorted, stacked, and bound planks, in an hour.
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![Logs at sawmill at Manitoulin Island [190-?]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aLogs_at_sawmill_at_Manitoulin_Island_(I0014072).jpg)
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