March 4, 2021 | 1:25 pm CST
White oaks (Quercus genus) are a plentiful hardwood in our Eastern and Southern forests. There are eight major species of oak trees that produce the lumber we call white oak, plus another 12 minor species. White oak trees have round ends on the leaves and sweet acorns that make excellent flour when dried.
White oak group:
Bur oak Quercus macrocarpa
Chestnut oak Q. primus
Chinkapin oak Q. muehlenbergii
Overcup oak Q. lyrata
Post oak Q. stellata
Swamp chestnut oak Q. michanxii
Swamp white oak Q. bicolor
White oak Q. alba
Overcup and swamp chestnut oaks are typically lowland oaks, growing in wet warm sites. Annual rings are at least 1/4-inch wide. These lowland species dry and machine with greater difficulty than the other species. They often are bacterially infected.
White oak wood has many desirable properties, including natural decay resistance, very high strength, and is impervious to liquids (except for chestnut oak). As a result, white oak has been used for railroad ties, ship building (especially the keel and ribs), bridges, fences, barrels for liquids (wine and whiskey), and mine timbers.
Compared to red oak, on the average, white oak is heavier, stronger, and frequently darker in color. White oak has much larger (longer and wider) ray cells (½ inch long in red and 1-1/2 inches or longer in white), giving white oak a very strong ray fleck pattern on the quartersawn surfaces. Today, the heavy grain, high figure, and dramatic ray fleck patterns of white oak make it highly desirable for Mission-style furniture and cabinets. Much of the native white oak lumber is exported to Japan and Europe. When properly aged, white oak makes excellent barrels for wine–probably the best oak wine barrels in the world. Whiskey barrels are another excellent use for oak.
Processing suggestions and characteristics
Density. The density of white oak averages about 46 pounds per cubic foot at 8 peercent MC. A piece of white oak lumber, 15/16” x 6” x 12’ weighs about 22 pounds.
Drying. White oak is very difficult to dry–harder than red oak in many cases. Surface checking, end checking, and honeycomb are the most common drying defects. As these defects develop very early in drying, close control of initial drying environments is required. End coating of all thicknesses is prudent. Warehouse predryers are probably the best option for 4/4 and 5/4; second best would be open sheds. Shrinkage in drying is around 8 to 10 percent.
Final moisture contents for white oak should be between 6.5 and 7.0 percent MC. Higher MCs cannot be accepted due to white oak’s high shrinkage; lower MCs result in excessive chipped grain.
Gluing and Machining. White oak is very unforgiving when gluing due to its high density. Surfaces must be flat, smooth, and freshly prepared. Clamp carriers are probably best for this wood. Any good woodworking adhesive can be used with excellent results.
Machining of oak is difficult due to its density unless machines and knives are precisely set. Chipped grain is common if knives are not sharp. Dull knives also result in a rough flatsawn surface where the large vessel cells are located. Correct MC is critical. With proper knives and machines, the surface is excellent in quality, however. Usually, machine tools need to have a larger tool (or sharpness) angle, thereby increasing the amount of metal in the tool. Sharpening may have to be more frequent. Slow feed rates or small depth of cuts will result in rapid dulling.
Stability. White oak moves quite a bit when the MC changes. Although it varies depending on species, the change is about 1 percent in size for each 3 percent MC change running across the grain parallel to the rings (tangentially), and about 1 percent size change for each 6 percent MC change across the rings (radially). The high tangential to radial difference means that lumber from near the center of the tree (usually the lower grade material) is prone to cupping.
Strength. The white oaks are one of the strongest native hardwoods. Bending strength (MOR) averages 13,000 psi. Hardness averages 1360 pounds. Stiffness (MOE) averages 1.6 million psi.
Color and Grain. White oak is typically a dingy white to light tan to dark brown, depending on the species. The annual ring patterns gives white oak a heavy grain appearance. The heavy ray fleck adds character to the wood. The large pores in oak will present some of the same finishing problems that red oak, hickory, hackberry, and ash do.
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