Any of the movements or shrinkages discussed thus far are natural, normal reactions to wood drying. These are expected and accounted for by those who cut or dry wood. For most of us these movements are not as severe. For more information see Woodworking Magazine Autumn , Issue 4. Most woodworkers use this guide to confirm what they are already doing. We know wood moves. We know you need to allow for movement. If you do the calculations, you begin to understand just how much wood moves.
Besides, most panels that we glue up, and any wide boards used in our projects, are generally not one type of cut. Most are a combination of quartersawn and flat-sawn, and some may be rift-sawn the face of the board meets the growth rings at angles between 30 degrees and 60 degrees.
With different grain patterns involved, to use the charts requires us to make judgment calls — a potential for error. Knowing that boards generally cup toward the bark side of the tree is a quick indication of how the piece should be surface planed.
Armed with that information, we can make calls that affect the way we work in the shop. This information is available from the numbers supplied by the Forest Products Laboratory. To get a general assessment of wood warp, divide the number given for tangential movement T by the radial movement number R.
The closer this ratio is to 1, the less warp you have to worry about. Mahogany and walnut, each with a 1. What is Warp? Warp is comprised of a few different movement issues. The three major movement issues we consider in woodworking are cup, bow and twist. Of the three, the most common warp is cup. A board cups when one face shrinks more in width than the opposite face.
The rule of thumb is that boards cup toward the bark side. An easy way to visualize this is to imagine that the growth rings are trying to straighten. While this is most often the case, you will find boards that cup in the opposite direction. Again, this is an issue in flat-sawn lumber. Information about cup in stock is important for a couple reasons.
First, if you know that in all likelihood the cup is facing the bark side, you can quickly ascertain the face that should be milled first at the jointer.
Attaching backboards is an example. Position the bark side of each board to the cabinet, then if the board were to cup, the movement would force the edges of each board tight to your case. Wood will shrink as it dries until it reaches EMC equilibrium moisture content or the proper level of moisture. Or oddly enough it will soak up the moisture in the air until it reaches EMC.
This process can take anywhere from days to months depending on the environment and type of wood. Wood can take up and release moisture indefinitely. Warped wood does not mean damaged beyond repair or unusable by any means. It may take a little extra time to fix, but there is no need to waste your money and throw away wood that could be fixed. Source — Wood Warping. There are many factors that can contribute to wood warping such as wood species, grain orientation, sunlight, uneven finishing, airflow, and temperature.
While some types of wood have a relatively high moisture content, other types have very low moisture content. As humidity increases, the moisture content of wood will also increase and the wood expands. As humidity decreases, the moisture content will also decrease and the wood will shrink. Thicker wood takes longer to both absorb and lose moisture. Quartersawn lumber will shrink and then expand about half as much as lumber that is flat sawn.
Source— Family Handy Man. Here are a few tips on how to store your wood the right way to prevent any of the wood from warping. Even if the wood was improperly stored where you purchased it, but if you store it the right way at home, it will be just fine. Green lumber should be stacked on stickers as soon as possible after sawing.
This improves air circulation between the boards, speeds drying, and prevents warping. Applying an end sealer to the boards will reduce splitting. Properly stacked lumber dries quickly in warm, dry weather. Softwoods like pine and cedar will air dry to suitable moisture content in as little as 6 weeks during the spring and summer months. Hardwoods like Maple, Oak, and Walnut will dry in 6 months. Little or no air drying takes place in wet damp weather.
Boards should be placed on stickers that must be uniform thickness and as long as pieces of lumber. Following these few storing techniques will prevent warping and will save you a lot of time needed to try and fix the warped wood later on. Source — Delmhorst Insrument Co. Source — Home Depot. Although any species of wood could warp, some types of wood are much more stable and far less likely to warp than others. Wood with a close grain has less of a tendency to warp than open grain.
The closer the grain, the less space between the wood fibers, reducing the possibility of shrinking. Hardwoods generally have a closer grain than softwoods, and the densest hardwood species grow in the tropics.
Many tropical species also contain natural oils that remain in the grain after the wood has dried. This prevents shrinkage. Because it is so hard, wood from these species is difficult to mill and work. Most of the species have been over-harvested, so the wood is rare and expensive.
The tendency for a board to warp depends on the species of wood and how the board was cut from the tree. The most stable board is cut from a hardwood tree with dense grain in a way to minimize shrinkage rates across the grain. Wide boards, even dense hardwood ones, are prone to warping if they come from the outside of the tree. On the other hand, even a softwood board may resist warping if it is primarily hardwood.
Because they have a close, symmetrical grain, quarter-sawn hardwood boards are usually the most stable. Any of these woods would be great for your DIY projects and are typically easy to work with, easy to fix if they do warp. You can avoid warped lumber fairly easily by careful selection.
Here are the basic things to look for when selecting lumber roughly in order of importance :. It is important to remember to always check the moisture content before use. Not only do you want to make sure that the area you are storing your wood in is free from moisture and humidity, but you also want to check the moisture content of the wood itself. Larger factories or manufacturers should have hygrometers in the storage area so you can keep track of the moisture in every area.
You should also have prong meters that will measure the moisture content of the wood itself from the surface to the interior. Curing your wood can be another defense against warping, and if done right, it can increase the longevity of the wood. You want the wood to be completely dry before you store it. By following these simple instructions, you can prevent your wood from warping:. You could also choose to have the ends of the wood sealed to prevent them from warping, which happens faster than in other areas of the wood.
This keeps the ends from warping by drying faster than the rest of the wood. Do you need wholesale lumber for your next job, or do you want some advice from a professional about how to store lumber to prevent warping? Get in touch with Curtis Lumber and Plywood to ensure you will get the best wood possible and the best advice to prevent your wood from warping!
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