Did you know that plywood is a great material for woodworking? This article will explain the reasons you should consider using plywood for your next project and what you need to know in order to select the right types and grades.
Plywood vs. Particleboard, MDF, and Even Lumber!
Some new woodworkers may dismiss plywood as they confuse it with other sheet goods, namely particleboard (also called chipboard) and medium density fiberboard (MDF), that are often used in the construction of cheap furniture.
While those materials are useful in many situations and are cheaper than plywood and solid lumber, they are not practical for many woodworking projects. Both particleboard and MDF can swell and come apart when exposed to moisture. They also present limited finishing options as paint or a clear coat are the only ways to hide their plain brown surfaces.
Particleboard and MDF are made of wood chips, sawdust, and other ground down wood fibers that are then bonded together with resin or other chemical binders then pressed into sheets.
Some woodworkers may also claim plywood is inferior to solid lumber, but there are many reasons to counter that argument. Let’s take a look at some of the benefits of using plywood for wood projects.
Plywood’s Structure Makes It Strong
Veneer core plywood is manufactured out of thin layers (“plies”) of wood that are glued together at different angles. Some grades of plywood will often have the plies arranged at right angles to each other.
Better grades of plywood have the plies arranged at various angles in addition to straight right angles. This method of manufacturing increases the strength of the plywood sheet in all directions.
This type of plywood, then, is basically thin boards glued together, resulting in a very strong material, especially compared to the glued together sawdust and wood chips that MDF and particleboard are made of.
In fact, a good quality grade of plywood may be even stronger than a comparable size piece of lumber. Because wood is made up of hollow fibers resembling a bundle of straws running the height of the tree (or length of a board cut from the tree), it is stronger along the grain than perpendicular or across the grain. Plywood, however, has nearly equal strength both parallel to and perpendicular to the plies. This strength in different directions results in very strong, large panels of wood.
Plywood Expands and Contracts Less Than Solid Wood
An advantage to plywood over wood is the fact it expands and contracts very little, if at all. Because wood fibers are hollow, they lose and absorb moisture, causing expansion and contraction as humidity levels rise and fall. This rate of expansion or contraction is about 1% for every 4% change in moisture content of the wood.
A 20” wide table top made of solid walnut wood will expand over ¼” when the moisture content of the wood changes from 12% to 7%, which is a reasonable amount of change to expect in winter months.
While one-quarter of an inch may not sound like much, that amount of movement can cause the top to crack if it were not attached to the table in a method to allow for the wood movement.
That’s why you should never glue a solid wood table top directly to the table frame. Rather, attach it using clips, figure 8 fasteners, or wood buttons that provide room for the top’s expansion and contraction. This video discusses how to allow for wood movement in an end table top.
Plywood Availability and Cost
Two other factors in favor of using plywood are its availability and cost compared to solid lumber. Most big box home improvement stores and local lumberyards carry plywood in a variety of species such as birch, oak, and maple. Additional species can be special ordered if your local building supply companies do not have it in stock.
The cost of a sheet of plywood can be less than the hardwood needed to make up the same amount of wood. For instance, an 8 foot by 4 foot, ¾ inch thick panel of cabinet grade cherry plywood is equivalent to 32 board feet of solid wood and can be purchased for around $100 per sheet. In contrast, at $7 per board foot, 32 board feet of the highest graded (FAS) cherry will run about $224, or more than twice the same amount of plywood.
As another example, you can buy a full sheet of cabinet grade oak plywood for around $70, compared to $166 for the same amount of solid oak lumber.
Plywood Can Look As Good As Solid Wood
It is much more common these days to see cabinet side panels made of plywood than solid lumber. But that doesn’t mean you can’t have the solid wood look because plywood can be purchased in either softwood or hardwood varieties. The most commonly available wood types are cherry, birch, oak, maple, and oak.
A sheet of cherry plywood can be just as beautiful as a cabinet side as a panel made of glued up solid boards. A high-quality grade of plywood with book matched veneer can be more aesthetically pleasing to some eyes than the random grain patterns and colors often present in lumber.
Plywood Does Not Require As Many Woodworking Tools To Use As Lumber
Newer woodworkers and those with a limited budget for tools often don’t have the tools needed to properly prepare solid lumber for woodworking. However, plywood can be used in place of lumber with a smaller number of tools.
When you join lumber together to make panels, a typical process is to first flatten one face of the board using a jointer. You next need to square up one long edge to the face of the board, again using the jointer. The board is then ripped to width on a table saw. Then, you run the board through a planer to square up the second face and to reduce the thickness of the board to the desired size.
Plywood, on the other hand, needs only to be cut down to size as the panels are flat and usually square to the edges. This requires using only a saw and not a plane or a planer and jointer
Although full sheets of plywood might be bulky to move around the shop until cut down to size, there are several ways to make dealing with panels easier. You can lay a sheet of plywood on a sheet of thick rigid foam insulation on the floor and use a circular saw to cut down the panel to rough size pieces. Finish cut the panels to size on the table saw, band saw, or miter saw.
Check out this great article by Ana White for her tips on cutting plywood with a circular saw: http://www.ana-white.com/2015/03/tips-cutting-plywood-circular-saw
How Plywood is Graded
Plywood is graded by its appearance and physical condition. Hardwood plywood face grades run from “A” to “E”, with “A” being the highest rating. Here are the face grades you’re likely to encounter:
|A – Used where the appearance is very important such as for cabinets and furniture. The veneer is matched for grain and color. No defects allowed except for small pin knots or burl grain that is common to the wood species.|
|B – Used where the natural look and characteristics of the species are desirable or acceptable. The color should be matched but grain matches are not necessary.|
|C – D – Used where the surface will be hidden or the more natural appearance is acceptable. The surfaces are sound, but there are no limits on the color variation allowed. Visible repairs in increasing sizes are allowed.|
Imported Hardwood Plywood Grades
Imported plywood is graded like domestic plywood but on different scales. The face grades for imported Russian (Baltic) Birch plywood panels are:
BB: Single-piece face veneer clear and free of defects with a light-uniform color
BB: Single-piece face veneer with generally even color. Small pin knots, mineral streaks, and 3-6 small color-matched patches allowed.
CP: Single-piece face veneer with unlimited patched repairs and unmatched color allowed.
C: Patches, open knots, and small veneer splits allowed.
Plywood Core Types
Plywood is manufactured in a variety of core types. These are:
Veneer Core – Constructed of a center veneer and crossband veneers glued to opposite angles on both sides of the center veneer. This type of plywood has excellent weight-bearing and bending strength and holds screws very well.
Combination Core: Contains either a center veneer core and a crossband veneer on both sides of the center and a layer particle board or hardboard under the face and back veneers. This type of plywood is consistently flat and possesses very good screw-holding ability.
Lumber Core: Made up of face and back veneers, a layer of crossband veneer, and edge-glued lumber in the middle. Lumber core plywood has good bending strength and holds screws well. This type of plywood is great for use as long or wide cabinet or closet shelves.
MDF Core: Consists of face and back veneers glued directly to an MDF core with no crossband veneer. MDF core plywood is often used in 33mm construction, like modern kitchen cabinets with Euro hinges.
Plywood Veneer Slicing Types
The method in which the face and back veneers are cut from a log dictate the grain patterns that appear on the finished plywood panel and the cost of the plywood. Two types of veneer cuts are utilized, plain slicing and rotary slicing.
Plain sliced or flat cut veneer is obtained when a log is turned a few inches at a time while being sliced. The log is moved over top of the knife, resulting in a single slice of veneer for each pass. Each slice of veneer is then stacked in the order it is cut from the log. This slicing method requires more work than rotary sliced veneer. The grain patterns of plain sliced or flat cut veneer more closely resemble that of flatsawn lumber.
Rotary slicing is done by spinning the log on a holder that resembles a gigantic lath. As the log spins, the veneer knife continuously cuts a very thin layer of veneer, resembling a roll of paper tissue being unrolled. The rolls of veneer contain swirling grain patterns that make it unattractive for nicer woodworking projects. However, this type of plywood is great for shop cabinets, jigs, and other utility pieces where appearance is not a huge concern.
Plywood Veneer Matching Techniques
The final thing to consider regarding the appearance of plywood is the method in which the face veneers are matched. Let’s take a look at each those matching techniques
- Plywood is slip matched when the veneer slices from the log are glued side by side in the order they were cut from the log. This results in a repeating grain pattern across the width of the panel.
- Book matching is done by turning over every other veneer slice to produce a mirror image at the joint. Book matched plywood has a very appealing look.
- Plank matched plywood is made by arranging pieces of veneers from different logs of the same wood species in a deliberate manner. This technique creates a panel of mismatched grain, often to achieve a rustic look.
- Plywood with a random-matched face is created by randomly picking veneer slices from the same log without considering the color or grain.
As you can see, plywood has lots of benefits making it worthy of consideration for use in your next wood project!