CORE OPTIONS AND OPINIONS
The materials used to make plywood’s inner core affect several important characteristics: weight, strength, rigidity, stability, flatness, screw-holding capability, consistency of thickness, and evenness of the veneer.
VENEER CORE is made up of many layers of hardwood bonded together. The layers are assembled with alternating grain direction, called crossbanding. This makes a strong, rigid, lightweight sheet with excellent screwholding capability. Because of these qualities, veneer core is my first choice in most cases.
PARTICLEBOARD CORE is the least expensive option. Like MDF core, it’s flat and stable with consistent thickness. But particleboard core is a bit worse in the screwholding category. Also, it’s a special-order product, at least from my lumberyard, whereas MDF core is readily available.
LUMBER CORE consists of edge-glued strips of wood, usually basswood. On both sides of the core, there’s a crossbanded veneer, then the face veneer. Like veneer core, it has excellent screwholding capability, strength and rigidity. But it’s considerably more expensive and harder to find than veneer core, so I almost never use it. However, it’s a good choice for long shelves.
MDF CORE has a few advantages over veneer core. The thickness is more consistent, and MDF gives a smooth, even surface for the face veneer. It’s also more stable and it’s typically flatter. However, MDF core isn’t as strong as veneer core, it doesn’t hold fasteners as well and it’s heavy. But if I’m making one-piece doors, I’ll choose MDF core every time because of its flatness and stability.
COMBINATION CORE weds the best attributes of MDF core and veneer core. The center cores are crossbanded hardwood, providing strength, light weight and screw-holding capability. The outer cores are MDF, giving a flat, uniform surface for the face veneers. However, combination core is a compromise: It doesn’t have the screw-holding capability and rigidity of veneer core, or the flatness and stability of MDF core.
BALTIC BIRCH AND APPLEPLY are top-notch veneer core plywoods, which you’ll only find at a lumberyard. Their 1/16-in.-thick core veneers offer better stability than typical plywood with 1/8-in.-thick core veneers. The raw edge is attractive when finished and often used as a design element. Baltic birch or ApplePly is my first choice for drawers and shop jigs. ApplePly is available in thicknesses from 1/4 in. to 1-1/2 in., and in many face veneer species.