Can You Run Plywood Through a Thickness Planer? The Pros and Cons Explained
Plywood is a popular material used in woodworking for its strength, versatility, and relatively low cost. Whether you're building furniture, cabinetry, or even flooring, plywood often makes up the backbone of many projects. But when it comes to finishing plywood for a clean, smooth surface, many woodworkers wonder: can you run plywood through a thickness planer? The simple answer is yes, but there are several considerations that you need to be aware of before doing so. Understanding these factors will help ensure you achieve the best results while protecting both your material and your planer.
At its core, a thickness planer is designed to remove material from a board to reduce its thickness and achieve a uniform surface. It's typically used on solid wood, but many woodworkers question whether it can also be used on plywood, which has a unique structure. Plywood consists of layers of wood veneer that are glued together, with the grain of each layer running in opposite directions. This cross-grain construction makes plywood strong and stable, but it can also create challenges when planing.
One of the main concerns when running plywood through a thickness planer is the risk of tear-out. Tear-out occurs when the blades of the planer pull up fibers from the surface of the wood, leaving rough, jagged edges. Plywood is particularly prone to this problem because of its layered construction. As the planer's cutterhead moves across the surface, it may cut into the edges of the veneer layers, leading to uneven surfaces and unsightly tear marks. This is especially true on the outer veneer layers, which are often thinner and more delicate than the inner layers.
To mitigate the risk of tear-out when planing plywood, there are a few strategies you can employ. One option is to use a planer with a helical or spiral cutterhead. These cutterheads feature smaller, offset blades that cut the wood in a slicing motion, reducing the likelihood of tear-out compared to traditional straight blades. A helical cutterhead also provides a smoother finish, which is particularly beneficial when working with plywood. Some high-end planers, especially those designed for professional or heavy-duty use, come equipped with these advanced cutterheads.
Another strategy is to use a planer with a slower feed rate. Slower feed rates give the cutterhead more time to make each cut, resulting in a cleaner, more controlled removal of material. This is particularly important when working with plywood, as it helps to reduce the chances of splintering or tear-out. Additionally, using a finer thickness setting and taking lighter cuts can help achieve a smoother result, especially when working with plywood sheets that are already close to the desired thickness.
While using a thickness planer on plywood can yield excellent results, it's important to be aware of the limitations of your planer. Standard thickness planers, especially lower-end models, may not be equipped to handle plywood with ease. Some planers can struggle with the density of the plywood, particularly if it's made from hardwood veneers. This can result in uneven cuts or a slower, more difficult planing process. For this reason, it's a good idea to check the manufacturer's recommendations for your specific planer to ensure that it is suitable for planing plywood.
Another potential issue when running plywood through a thickness planer is the possibility of damaging the planer itself. If the plywood has any defects, such as knots or gaps in the veneer layers, these can cause the planer's blades to become dull or even chip. Additionally, if the plywood is warped or uneven, it can put additional strain on the planer and cause uneven results. In some cases, these issues could even lead to permanent damage to the machine. To avoid this, it's a good idea to inspect the plywood before running it through the planer, and to make sure it is flat and free of significant imperfections.
Plywood thickness can also vary depending on the manufacturer, and this may affect the planer's performance. For example, some plywood sheets may have a thickness that exceeds the capacity of a standard benchtop planer. If the plywood is too thick, the planer may struggle to handle the material or produce uneven cuts. In such cases, it may be necessary to trim the plywood down using a table saw or other cutting tool before running it through the planer.
It's also worth considering the type of plywood you're working with. While hardwood plywoods are typically more durable and less prone to tear-out, softer plywoods, such as pine or fir, are more likely to splinter when planed. If you're working with softwood plywood, it's especially important to take precautions like reducing the feed rate, using a fine-cut setting, and even applying masking tape to the surface of the plywood. The tape helps to support the surface of the wood, reducing the risk of tear-out by keeping the fibers in place during the planing process.
For some types of plywood, such as baltic birch or marine plywood, the layers are more uniform and of higher quality, making them better candidates for planing. These types of plywood are generally less prone to delaminating or splintering and can often be planed with better results. On the other hand, lower-quality plywood with poor veneer bonding or softwood construction may present more challenges when run through a thickness planer.
In addition to tear-out, another consideration when planing plywood is the potential for uneven surfaces. If the plywood is not perfectly flat or if the planer is not properly aligned, the board could be left with waves or dips after planing. To prevent this, ensure that your planer is well-maintained, the blades are sharp, and the machine is properly calibrated. It may also be helpful to use a sled or support board when feeding the plywood through the planer, especially if you're working with larger sheets.
In conclusion, while you can certainly run plywood through a thickness planer, it's important to consider the type of plywood, the condition of the material, and the capabilities of your planer. With the right precautions, such as using a planer with a helical cutterhead, adjusting the feed rate, and inspecting the plywood for imperfections, you can achieve a smooth, even finish on your plywood. However, if you're working with low-quality plywood or exceptionally thin sheets, it might be better to use an alternative method, such as sanding or using a planer with a finer setting, to achieve the desired results. As with any woodworking project, understanding your tools and materials is key to ensuring success and getting the best results possible.
