Everything you need to know about PLYWOOD Or… at least a lot… What is a Size and Thickness of a Sheet of Plywood? Submitted by: Woody Wall Standard Sheet Most finished 4x8 sheets of plywood will measure exactly 48 x 96 inches. Some exotic finishing plywoods may be slightly larger to allow for cutting. Oversized Certain sheet goods such as Melamine are larger by up to 1 inch in each direction to compensate for edge chipping or damage. Other Some types of plywood such as baltic birch may come in different sizes of sheets. In this case, the size of the sheet will be indicated.
Sheet Thickness Sheet goods vary widely in their actual thicknesses, based on the type of plywood, manufacturer, origin, and batch. When the precise thickness of the sheet is important, it is always wise to measure. A general though imprecise conversion of metric and imperial thicknesses would be as follows:
Plywood Terminology Submitted by: Woody Wall Back Back of plywood panel - The side of a panel that is of lower veneer quality on any panel whose outer plies (front and back) are of different veneer grades. Back ply of a plywood panel - The outer veneer on the back side of a panel. Borer holes - Voids made by wood-boring insects, such as grubs or worms. Broken grain - A (leafing, shelling, grain separation) separation on veneer surface between annual rings. Butt joint - A straight joint in which the interface is perpendicular to the panel face. An end butt joint is perpendicular to the grain. Centers - Inner layers whose grain direction runs parallel to that of the outer plies. Some centers consist of parallel laminated plies. Construction (panel construction) - Term referring to detailed manner in which veneers are assembled and/or thickness of veneer used, e.g. “4-ply/3 layer construction,” “2.5mm (1/10-inch) face and back,” etc. Face
Face of the plywood panel - The side of a panel that is higher veneer quality on any panel whose outer plies (front and back) are of different veneer grades; either side of a panel where the grading rules draw no distinction between outer plies. Face ply of a panel - The outer veneer on the face of a panel. Finger Joint - A term indicating the method by which panels or sections of panels have been joined to create longer lengths or widths by means of a well-bonded series of sloped scarf cuts resembling fingers. Grade name - Term used to identify panels having special characteristics and/or requirements such as Marine, Decorative and Underlayment. Heartwood - Nonactive core of a log generally distinguishable from the outer portion (sapwood) by its darker colour. Knot - Natural characteristic of wood that occurs where a branch base is embedded in the trunk of a tree. Generally the size of a knot is distinguishable by (1) a difference in colour of limb wood and surrounding trunk wood: (2) an abrupt change in growth ring width between knot and bordering trunk wood; (3) a diameter of circular or oval shape described by points where checks on the face of a knot that extend radially from its center to its side experience an abrupt change in direction. Knotholes - Voids produced by the dropping of knots from the wood in which they were originally embedded.
Delamination - A visible separation between plies that normally receive glue at their interface and are firmly contacted in the pressing operation. Wood characteristics, such as checking, leafing, splitting and broken grain, are not to be construed as delamination. Shop-cutting panels - A panel which has been rejected as not conforming to a standard grade because of deficiencies, other than adhesive bond quality, which prevent it from meeting the requirements of this standard. Blistered panels are not considered as coming within the category of “shop-cutting panel.” Localized delamination occurs as a result of a deficiency. However, shop-cutting panels are suitable for cut-up use where cutting eliminates the deficiency in the portion of the panel salvaged.
Hardwood Plywood Panel Construction Submitted by: Woody Wall Hardwood Plywood Panel Construction Plywood is layers of veneer, or plies, glued together, with the grain of the plies alternating in direction. The number of plies varies according to the thickness required from 3-ply to multi-ply. Various core are available including veneer core, lumber core, and fiberboard core.
materials particleboard core
Panel Construction Veneer Core: Based almost entirely on a 48” x 96” sheet. Occasional 120” material is available. This is a standard veneer crossbanding technique where 3, 5, 7 or 9 veneer plies are used. Lumber Core: This is a 5 ply construction made up of two face veneers, two crossband veneers and a solid lumber core. The core is usually made up of edge-glued strips of lumber 1-1/2” to 2” wide. The core is basically solid and free of void which gives unusual strength and high resistance to twisting or warping. Usually 3/4” thick.
Particle Core: This is a carefully engineered product. Particleboard is available in thicknesses of 1/4” to 1-1/8” and in various widths. Fiberboard Core: Similar to particleboard with the additional advantage of uniform density throughout. Available in thicknesses from 1/4” to 1-1/8” and in various widths. Edges can be machined and easily finished. Fiberboard is the most stable of composition core material. Veneer Cutting The two principal methods of cutting veneer are rotary cutting on a veneer lathe where the log centered on a lathe and turned against the knife like peeling an apple; and slicing on a veneer slicer, where parallel slices through the log produce a variegated figure in the wood. The method selected depends on the species, characteristics of the logs and grain.
How to Distinguish between American and Canadian Plywood Grades? Submitted by: Woody Wall Canadian Plywood Grades Good Two Sides - Fully sanded on both sides, may contain neat wood patches and inlays and synthetic filler is allowed.
B/BB- Is the same as above but is used for describing poplar as opposed to fir. B is a grade of veneer that applies to Fir and Poplar. Good One Side - Fully sanded face allowing neat wood patches and inlays, back is sanded and has open knots. Synthetic filler is allowed. B/C - Same as above when describing poplar. Industrial One or Two Sides - Basically the same as one or two sides but allows more patches per face and allows for the grain of the wood to be a bit more feathery or raised. Factory - A fall down from good one side, face is still fully sanded but allows for a defect on the exterior of the panel, such as a sand through or piece of veneer missing, but must be able to make a a 4’ x 7’ or 3’ x 8’ panel with no defects. Sanded D - Can be anything less than that allowed for a factory panel. Is lowest grade of sanded plywood. Does not include delamination. Grading will vary from mill to mill. Delamination is allowed as a part of a visible defect. Select Sheathing - Fully sanded or skip sanded face with small tight knots and allows for larger and open knots on back. May not be sanded. D Grade - All fall down from above, including some face or back veneer missing or loose. Cull - Allows for any possible imperfection - delamination, off square or mis-sized.
American Plywood Grades ACX Superply - Patch free, hardwood face veneer, very tight grain, buff sanded very smooth. Excellent for paint. AC Premium - Up to 10 repairs per panel, wood and synthetic, no knots. ACX - Up to 18 repairs per panel, some pin knots, very slight. BC Premium - Unlimited repairs, no knots, some minor repaired splits. BCX - Unlimited repairs, tight knots up to 1” across grain, some minor veneer splits allowed. C Veneers - Open knots up to 1!, tight knots up to 1-1/2”, unlimited repairs, discolorations, sanding defects, limited splits. This is a veneer grade and does not describe a sheet of plywood. This grade of veneer is not always a sanded item. Off Grades - Sanded Shop (Factory) - Fall down from A & B sanded products, 80% usable panel. Up to 20% allowed for delams, edge and corner damage, sanding defects. Varies from mill to mill. The actual grade does not require any % as usable. PTS (Plug and touch sanded) - Fall down from APA rated underlay products. 80% usable panel, same as above. Could have core voids not allowed in on grade underlay panels. PTS is a manufacturing process that could be performed on any sheet of plywood. CD Shop - Fall down from C face veneers, otherwise same as Sanded Shop above. CD shop is not normally sanded. Blows - Delaminated veneers, could be pocket delams, edge delams or whole veneer section delams.
Hardwood Plywood Species Submitted by: Woody Wall Knotty Pine Colour: Nearly white sapwood; heartwood, cream to light to reddish brown. Pattern: Straight grain, not contrasty, fine texture Thickness: 1/4” and 3/4” Red Oak Colour: Grayish white to pale reddish brown sapwood, heartwood flesh coloured to light reddish brown. Pattern: Straight grained, course texture. Thickness: 1/8”, 1/4”, 1/2” and 3/4”.
Birch Colour: Creamy white sapwood, pale brown heartwood. Pattern: Straight close grain, fine uniform texture. Thickness: 1/8”, 1/4”, 1/2” and 3/4”. Walnut Colour: Sapwood whitish to yellowish brown, heartwood light grey-brown to rich chocolate brown. Pattern: Straight to interlocking or curly, wavy grain. Thickness: 1/8”, 1/4”, 1/2” and 3/4”. Cherry Colour: Sapwood is nearly white, heartwood light pinkish brown. Pattern: Fine, straight close grain. Thickness: 1/4”, 1/2” and 3/4”. Maple Colour: Sapwood white; heartwood gray-white to pinkish tinge. Pattern: Straight grain, fine texture. Thickness: 1/8”, 1/4”, 1/2” and 3/4”.
Beech Colour: The heartwood is very pale pink-brown. Pattern: Straigh grain and fine, even texture. Thickness: 1/4” and 3/4”. Ash Colour: Sapwood nearly white, heartwood grayish brown to light brown. Pattern: Straight grain, course, even texture. Thickness: 1/4” and 3/4”. Quarter Sawn White Oak Colour: Varies in colour from pale yellow-brown to biscuit with a pinkish tinge. Pattern: Straight grain, with silver grain. Thickness: 1/4” and 3/4”. Hickory Colour: Heartwood is brown or reddish brown. Pattern: Straight grained, but may be wavy or irregular. Thickness: 1/4” and 3/4”. Alder Colour: Heartwood is pale yellow to reddish-brown Pattern: Straight grained and of uniform texture. Thickness: 1/4” and 3/4”. Vertical Grain Fir Colour: Heartwood is pale buff-reddish to yellowish. Pattern: Straight grained Thickness: 1/4” and 3/4”