question: Why is lumber sold based the size it was before it went into the planer?
comment: Because "two by four" is easier to say than "one and a half by three and a half". Long ago, the wood was just raw cut from the sawmill and whanged together into a house. But raw wet wood has bugs and moisture. As it dries it warps. Consumers don't like warped houses or bugs, so to satisfy demand they started pressing, straightening and drying the wood before hand. But they never changed the size or jigs of the saws that cut the wood out of the log, which is always wet. Carpenters, happy to not have to deal with warped buggy wood simply adjusted to the fact that a 2x4 was really 1.5x3.5, and made the corresponding adjustments when they were drawing out their framing etc.** Any carpenter or framer who is any good knows the true dimensions of a board and can deal with it probably without even thinking about it. Us weekend warriors though have to be careful to do real world lumber math. Having said that you can get true size treated lumber (a 2x4 that is actually 2x4) but it will cost you a fortune. **and this adjustment happened so long ago and just became "standard" accepted practise that noone ever bothered to go back and change it.
passages: It was then determined by Georgia-Pacific, which Rivendell did not dispute, that the two Quote Screen systems only had two common attributes: bundle sizes and board-footage conversions. These two attributes were determined to be standard constraints of the lumber industry and thus public knowledge.
   Section::::Historical methods.
  
  Historically, in the Pacific Northwest, logs were first sold after they were delivered to the water and rafted to the mill. Bundle rafts have bundles of logs that are tightly fastened together and some logs are well below the water line. Consequently, log scalers would walk the rafts and measure and grade the logs in the water. When logging was done by hand, the fallers and buckers were often paid on a piecework basis so the individual workmen's production was scaled daily as well. Presently, few logs are ever rafted.
  
  Section::::Ramp scaling.
   Timber cruisers also estimate the volume of timber, for example in a timber sale where the timber is sold on the stump, and can see the logs and where limbs grew on a tree, especially the lower logs in a tree which have the most volume and often the best grade of log and thus often the most value, better than a scaler. However, rollout scaling helps the scaler do this better than truck scaling or, in the Canadian province of British Columbia, in a log raft. The better the wood quality and the bigger the size of the logs, the better it is to scale logs when they are "rolled out".
   BULLET::::- Debarking removes bark from the logs.
  
  BULLET::::- "Decking" is the process for sorting the logs by species, size and end use (lumber, plywood, chips).
  
  BULLET::::- A sawyer uses a head saw (also called head rig or primary saw) to break the log into cants (unfinished logs to be further processed) and flitches (unfinished planks).
  
  BULLET::::- 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.
  
  BULLET::::- "Edging" will take the flitch and trim off all irregular edges leaving four-sided lumber.
   It is notable that the footers are set in a different typeface to the main body text. The former is possibly Small Pica No.1, identified from the printer's catalogue, while the footers are in a reduced serif form, and at a slightly smaller size. There is kerning for the uppercase letters, in neither the body nor footer types. The title page is set in a mixture of title types that Neill & Co. offered:
  
  Section::::Construction.:Argument for preconception.
   The mill originally cut soft wood timber for cases. This was cut to the required lengths and then packaged for delivery to the farmers who assembled the cases. The mill subsequently moved into cutting timber for pallets, and hardwood milling for electricity pole cross-arms and railway sleepers. In 2007, the mill was cutting softwood for assembly into packing cases for glass. It is one of the few sawmills of its era that is still operating on the North Coast.
  
  Section::::Description.
   The following paragraph is exactly backwards from North American cultural practices where finished retail and rough lumber share the same terminology, as is discussed in the paragraph after about 'architects, designers, and builders':
  
  In rough sawn lumber it immediately clarifies that the lumber is not yet milled, avoiding confusion with milled dimension lumber which is measured as actual thickness after machining. Examples – 3/4", 19mm, or 1x.
   Timber smaller than the 8th class were called "unclassed" (等外). The width of a timber is referred to as one "timber" (材), and the dimensions of other structural components were quoted in multiples of "timber"; thus, as the width of the actual timber varied, the dimensions of other components were easily calculated, without resorting to specific figures for each scale. The dimensions of timbers in similar application show a gradual diminution from the Sui Dyansty (580~618) to the modern era; a 1st class timber during the Sui was reconstructed as 15×10 (Sui Dynasty inches, or 2.94 cm).
  
  Section::::Dimensional lumber.:North American softwoods.
   As previously noted, less wood is needed to produce a given finished size than when standards called for the green lumber to be full nominal dimension. However, even the dimensions for finished lumber of a given nominal size have changed over time. In 1910, a typical finished board was . In 1928, that was reduced by 4%, and yet again by 4% in 1956. In 1961, at a meeting in Scottsdale, Arizona, the Committee on Grade Simplification and Standardization agreed to what is now the current U.S. standard: in part, the dressed size of a 1-inch (nominal) board was fixed at  inch; while the dressed size of 2 inch (nominal) lumber was "reduced" from  inch to the current  inch.
   Also in North America, hardwood lumber is commonly sold in a "quarter" system, when referring to thickness; 4/4 (four quarter) refers to a board, 8/4 (eight quarter) is a board, etc. This "quarter" system is rarely used for softwood lumber; although softwood decking is sometimes sold as 5/4, even though it is actually one-inch thick (from milling 1/8th inch off each side in a motorized planing step of production).
  
  The "quarter" system of reference is a traditional (cultural) North American lumber industry nomenclature used specifically to indicate the thickness of rough sawn hardwood lumber.
   Section::::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.
  
  BULLET::::- After trees are selected for harvest, the next step in logging is felling the trees, and bucking them to length.
  
  BULLET::::- Branches are cut off the trunk. This is known as "limbing".
  
  BULLET::::- Logs are taken by logging truck, rail or a log drive to the sawmill.
  
  BULLET::::- Logs are scaled either on the way to the mill or upon arrival at the mill.
   Tree height is measured to a merchantable top, the point at which a tree can be accepted for use by a sawmill. This point can be reached either by defects (extreme sweep, crook, deviating branching, or other defects) or at a diameter limit for very straight trees. A common cutoff is diameter, which is acceptable for pulpwood.
  
  Section::::History.
   The most commonly used thickness range is from . The sizes of the most commonly used plywood sheets are 4 x 8 feet (1220 x 2440 mm) which was first used by the Portland Manufacturing Company, who developed what we know of as modern veneer core plywood for the 1905 Portland World Fair. A common metric size for a sheet of plywood is 1200 x 2400 mm. is also a common European size for Baltic birch ply, and aircraft ply.
   Woodworking machinery that perform a similar function as hand planes include the jointer and the thickness planer, also called a thicknesser; the job these specialty power tools can still be done by hand planers and skilled manual labor as it was for many centuries. When rough lumber is reduced to dimensional lumber, a large electric motor or internal combustion engine will drive a thickness planer that removes a certain percentage of excess wood to create a uniform, smooth surface on all four sides of the board and in specialty woods, may also plane the cut edges.
  
  Section::::History.
   In some jurisdictions, there are still places where the logs arrive via railroad car, and here they can be left for rollout scaling.
   The NHLA has a long history of being involved in the national and international issues that affect the hardwood lumber industry. In 1976, the hardwood lumber industry was concerned with the long-standing practice of the footage as an allowance for shrinkage in lumber measured after kiln drying. This practice was challenged as being misleading, and there was a difference of opinion among industry leaders as to how this issue would be resolved. In July of 1977, the National Conference on Weights and Measurements adopted a statement outlining the proper methods for measuring kiln-dried lumber, and this statement has been thus added to each official NHLA Rule Book since that time.
   BULLET::::- Glulam beams – created from 2×4 or 2×6 stock by gluing the faces together to create beams such as 4×12 or 6×16. As such, a beam acts as one larger piece of lumber – thus eliminating the need to harvest larger, older trees for the same size beam.
   Section::::Uses.
  
  Although smaller firewood splitters are intended for home, there are now many commercial units available. Some commercial splitters are part of a 'firewood processor' that saw logs of timber into lengths, split them, and then carry the wood up an inclined conveyor onto a pile or into a bag, truck or trailer. Specialty producers such as those producing maple syrup use units that split 4 foot lengths. Machines that split and point wood for fence post also exist though they are few in number as it is generally safer and more convenient to saw the posts.
   BULLET::::- Timber columns may be classified as short columns if the ratio of the length to least dimension of the cross section is equal to or less than 10. The dividing line between intermediate and long timber columns cannot be readily evaluated. One way of defining the lower limit of long timber columns would be to set it as the smallest value of the ratio of length to least cross sectional area that would just exceed a certain constant K of the material. Since K depends on the modulus of elasticity and the allowable compressive stress parallel to the grain, it can be seen that this arbitrary limit would vary with the species of the timber. The value of K is given in most structural handbooks.
   Dimensional lumber is available in green, unfinished state, and for that kind of lumber, the nominal dimensions are the actual dimensions.
  
  Section::::Dimensional lumber.:Grades and standards.
  
  Individual pieces of lumber exhibit a wide range in quality and appearance with respect to knots, slope of grain, shakes and other natural characteristics. Therefore, they vary considerably in strength, utility, and value.
   In North America, market practices for dimensional lumber made from hardwoods varies significantly from the regularized "standardized 'dimension lumber' sizes" used for sales and specification of softwoods – hardwood boards are often sold totally rough cut, or machine planed only on the two (broader) face sides. When Hardwood Boards are also supplied with planed faces, it is usually both by random widths of a specified thickness (normally matching milling of softwood dimensional lumbers) and somewhat random lengths. But besides those older (traditional and normal) situations, in recent years some product lines have been widened to also market boards in standard stock sizes; these usually retail in big-box stores and using only a relatively small set of specified lengths; in all cases hardwoods are sold to the consumer by the board-foot (), whereas that measure is not used for softwoods at the retailer (to the cognizance of the buyer).
   To scale this up to a hectare level the result would have to be multiplied by the number of trees of that size. This is called the blow up factor.
  
  Section::::Tools used in inventory.
  
  BULLET::::- Biltmore stick – utilizes ocular trigonometry to quickly measure diameter and height
  
  BULLET::::- Diameter tape – cloth or metal tape that is wrapped around the bole, scaled to diameter
  
  BULLET::::- Tree caliper – two prongs connected to a measuring tape or stick are placed around the most average part of the bole to determine diameter
   Most trailered mills position the log on top of the trailer; some models have hydraulic log loading arms and some do not. Raising heavy logs without hydraulics can be a problem. There are portable mills with rails on the ground allowing a log to be positioned easily without hydraulics.
  
  Section::::Uses.
  
  The portable mills can cut lumber with speed and accuracy, though the subsequent steps of "planing" and "drying" must still be performed to produce finished lumber. Commodity lumber in standard sizes can be made this way.
   BULLET::::- Quarter sawn and rift sawn – These terms have been confused in history but generally mean lumber sawn so the annual rings are reasonably perpendicular to the sides (not edges) of the lumber.
  
  BULLET::::- Boxed heart – The pith remains within the piece with some allowance for exposure.
  
  BULLET::::- Heart center – the center core of a log.
  
  BULLET::::- Free of heart center (FOHC) – A side-cut timber without any pith.
  
  BULLET::::- Free of knots (FOK) – No knots are present.
  
  Section::::Dimensional lumber.
   Volume tables created with Girard form class use the assumption that trees of the same diameter and merchantable height have similar rates of taper above the first log. This implies that volume differences in trees with the same diameter and merchantable height can be mostly attributed to taper variations in the first log. Volume tables using Girard form class are composite tables and are created independently of tree species.
  