![]() The following symbols and formulas apply to rectangular beam cross sections: Section Modulus (S) is the moment of inertia divided by the distance from the neutral axis to the extreme fiber of the section.Ĭross Section is a section taken through the member perpendicular to its longitudinal axis. Moment of Inertia (I) of the cross section of beam is the sum of Table the products of each of its elementary areas multiplied by the square of their distance from the neutral axis of the section. Neutral axis, in the cross section of a beam, is the line in which there is neither tension nor compression stress. For convenience, the following are formulas to calculate the section properties of rectangular beam cross sections. all you need to do now is plane or cut them to size and finally to leght.Īlways work safely use wood and machinery you can handle and is designed to for the job you are using it for.Section properties are used in various design calculations. when this is done you will have safely made your rough cut board with two, 90 degree, flat surfaces. Once this is done you can start jointing another surface that is 1/4 turn of the board, so that now the surface you jut jointed in is now being used to fun along the fence of the joint. Once you have made this cut, you can take the rough lumber off cut to your jointer and joint that first edge to a nice clean flat surface. This can then be clamped to your rough cut lumber as a fence, and now you have a safe, accurate way of starting to break down your rough cut lumber.ĭepending on the power of you circular saw, the thickness and type of wood you are cutting, you may need to make a few passes with the saw, making each pass slightly deeper until the board is cut though. It is best to try and use some sort of a fence to let the circular saw ride along as you cut the length of the board, and one of the best things to use is factory edge of a piece of plywood, cut about 4 inches wide along the length of the sheet. You can often get way with purchasing less expensive circular saw as long as you put a good blade on it. If you do NOT have big table saw with a powerful motor and nice large out feed table, or a big band saw, the next best, and safest alternative is to use circular saw. You often need a pretty substantial band saw, but if you are only cutting 4-quarter boards, most 14 inch band saws should handle this. Using a good big band saw is preferable over any table saw in at least making the first cut through a rough cut board. IF you have a sufficiently powerful table saw, and a good out feed table, the only safer way to start dressing lumber is draw a straight line where the first cut will be, then "free hand" the board through the bandsaw. This is often a BAD idea because almost always rough cut boards will have a bend one way or another in them and there is no way they are going to be able to slide through a table saw with the fence attached, and make any kind of a decent cut. This ensures you are cutting off and planer or jointer snipe and any checking that invariably happens at the ends of boards.ĭuring the process of dressing rough cut boards many novice woodworkers will attempt to cut rough wood down on their table saw. The LAST cut you should be making is cutting the dressed board to length. The industry wide rule of thumb in dressing lumber is that two of the sides of a board are planed flat and 90 degrees to one another first, then the other two sides are planed or sawn appropriately. thinner lumber such as 4 quarter (one inch thick) is less a bit easier to work with but BOTH can be a hazard, and here'w why. ![]() Most lumber as it dries will bend and move in more than one plane creating what is termed a "propeller" shape.ĭressing this lumber down can be a real hazard if you are not careful because of the the way the wood is warped, and especiallt if you are working with 8 or 9 quarter inch thick boards ( 2' - 2 1/2'). Some wood will bend and move slightly while other pieces will bend wildly out of shape. The problem with this process is that frequently your wood will warp and bend as it dries, which is normal. Of course the disadvantage is that you have to dry it yourself, which takes time (yes this can take up to 3 or 4 years with some hardwoods), and then in order to make it useable, you need to break it down or "dress" the lumber (at least in most cases) which simply means making it useable for woodworking projects. ![]() The most economical way to purchase lumber is to buy green, rough cut lumber. ![]()
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