Sheet goods

The basic structural component of cabinetry is some form of sheet ootids; most frequently plywood. Other commonly used sheet goods are particle-board, fiberboard, melamine panels and hardboard. These materials come in handy when you need to cover a broad project area without including seams. Sheet goods are dimension ally stable (there is no substantive wood grain to contend with) and relatively inexpensive, when compared to the price of solid lumber. You'll turn to them time and time again for different woodworking applications. Here is an overview of the options you'll find at most home centers and lumberyards:

Plywood. Plywood is fashioned from sheets of wood veneer, primarily pine and fir. By orienting the wood grain of each laminated sheet so adjacent sheets are perpendicular, the product is able to withstand greater stress than construction lumber of the same thickness, [n addition, it is more dimensionally stable.

Most lumberyards stock furniture-grade plywood in several thicknesses and face veneer options (pine, red oak, birch and maple are the most common face veneers). Lumberyards can order plywood with dozens of additional veneer options.

Choosing the right plywood for your woodworking project is an important task. In addition to the various core, thickness and face veneer options, you'll also need to make a decision on the plywood grade. Basically, there are two grading systems in use today. The one most people are familiar with is administered by the APA (Engineered Wood Association, formerly the American Plywood Association) The APA grade stamps (See Illustration, next page) are found on sanded plywood, sheathing and structural (called performance-rated) panels. Along with grading each face of the plywood by letter (A to D) or purpose, the APA performance-rated

NOTICE

Partldeboard and MDF usually Contain urea formaldehyde re$ln$ that continue to emit low levels of formaldehyde gas for at (east six months as they cure. People with high sensitivity to chemical vapors should limit the number of composite panels added to a room at one time. Always wear a particle mask or respirator as required and provide adequate dust collection and ventilation when cutting or shaping these products.

Mdf Dust Exposure

PARTICLE - , BOARD is used almost exclusively as a substrate tor plastic laminate or veneer, especially for countertops. It is Inexpensive but lacks sufficient strength to be used tor shelving or structural members.

Panel grade

(face/back)

Exposure rating

(absence of exposure rating indicates interior only)

stamp lists other information such as exposure rating, maximum allowable span, type of wood used to make the plies and the identification number of the mill where the panel was manufactured. Many hardwood-veneer sanded plywood panels are graded by the Hardwood Plywood and Veneer Association (HPVA). The HPVA grading numbers are similar to those employed by APA: they refer to a face grade (from A to E) and a back grade (from 1 to 4). Thus, a sheet of plywood that has a premium face (A) and a so-so back (3) would be referred to as A-3 by HPVA (and AC by APA).

Particle board: Partieleboard possesses several unique qualities that might make it a good choice for your next built-in project-—particularly if the projcct includes a counter or tabletop. Partieleboard is very dimension ally stable (it isn't likely to expand, contract or warp); it has a relatively smooth surface that provides a suitable substrate for laminate; it comes in a very wide range of thicknesses and panel dimensions; and it is inexpensive. Rut partieleboard does have some drawbacks: it lacks stiffness and shear strength; it has poor screw-holding ability; it degrades when exposed to moisture; it's too coarse in the core to be shaped effectively; and it's heavy.

Medium-density fiberboard (MDF): MDF is similar to partieleboard in constitution, but is denser and heavier. The smoothness and density of

Understanding sanded plywood grade stamps

EXPOSURE 1 000

- Grading agency

GROUP 1 Assoe,ation WV Species group number face veneer, from 1 (strongest) to 5 (weakest)

ill I.D. number

Product standard number denotes which federal product classification standard was used for grading

Every sheet of plywood Is stamped with grading Information. On lower-grade panels, such as exterior sheathing, the stamp can be found in multiple locations on both faces. Panels with one better-grade lace are stamped only on the bach, and panels with two better-grade faces are stamped mi the edges.

MDF make it a good substrate choice for veneered projects; the rougher surface of partieleboard and most plywoods do not. bond as cleanly with thin wood veneer. You car even laminate layers of MDF to create structural components that can be veneered or painted. MDF is also increasing in popularity as a trim molding material.

Melamine board: Melamine is fashioned with a partieleboard core with one or two plastic laminate faces. Thicknesses range from Va to 3A in. Stock colors at most lumber yards and building centers generally are limited to white, gray, almond and sometimes black. The panels are oversized by 1 in. (a 4 x 8 sheet is actually 49 x 97 in.) because the brittle melamine has a tendency to chip at the edges during transport. Plan to trim fresh edges.

Face grade descriptions

iu Smooll surface "natural tirtsli" veneer Select, eft heartwood or all sapwood. Free of open ieiects.fc m\ ™ more than six repairs, wod wfy per4xf! pare), marie paralef to pr epJ iiefl-matcirci! iorjiain and cote.

- Smooth, portable. Not more than IS neatly made repairs, host, sled or miter type, and parallel to grain, " pennilteri. May be tised for natural finish»less demanding applications. SjnMc (cpairs pamittol.

n Solid surface. Shims, circular repair plugi and tigh kmts to 1 if. amiss grain permitted. Seme mitor splits " permitted. Synthetic repairs permitted.

Q iitffwtfl C veneer with splits United to Win. width arc! knntholes ard borer holes limited to ^ x Vj in. Plugged Admits some brutal grain. Synthetic repairs permitted.

Tight lurts to l^ifl-Kmihotes to i in. across grain and some lfeii it total width of toots and c knotholes is within spratled limits. Syolhelor wood repairs. Discoloration and sanding defect that do not ifnpak streitglh permitted. Li« led spite allotted, Slttchmg permitted,

k hunts and knnthob to % it. across grain and V? in. ¡¡¡rg.j wthin specified limits, limited spits are ^ permitted. Stitching permitted, lotted lo Interior and Exposure 1 or 2 panels.

Source: Engineered Wood Association

Plywood veneer grain patterns

1 ! j' ' " ' ! !! 1 1 L : 1

1

Rotary cut Sliced (plain-sawn)

i ! j Hi I

Sliced (quarter-sawn)

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Wood Working 101

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