Working with plywood

Working with solid wood is a joy in so many ways. When you see a minor defect, you have material thickness to sand, scrape and plane. But for larger case goods, such as cabinetry and bookcases, solid wood isn't always practical. Covering large expanses with solid lumber that has to be milled, edge-glued and planed can be very time-consuming and cumbersome. Sometimes quality, veneered sheet goods are the best option.

Choosing plywood

Sheet goods come in a wide variety of grades and surface types. Particleboard-core stock is less expensive, but has a number of disadvantages, such as excessive weight, less holding power for screws and higher glue content, which dulls tools faster. MDF-core stock is sometimes available, which is even heavier but very flat. My preference is veneer-core stock, which is made of alternating layers of less expensive wood, such as poplar. It holds screws well for hinges or other hardware, and it is much lighter than particleboard- and MDF-core stock.

Ripping plywood

Some special techniques are necessary to rip plywood. While I normally use a rip blade for solid wood, it doesn't cut veneer-core plywood quite as well. Because every other layer in the core is actually a cross cut, a rip blade makes a ragged cut in those layers, preventing edging from adhering as tightly. A combination blade does the best job; it is the best compromise when you need to both rip and cross cut simultaneously.

Remember that you can't use your jointer and planer with plywood, and that includes straightening edges before applying edging. MDF and particleboard cores will ruin your jointer knives in a hurry. Veneer-core stock will chip the knives on every end-grain layer, leaving a striped knife pattern on all your solid-wood stock afterward. Jointer and planer knives do not like end-grain.

Having to get a near-perfect edge straight off a tablesaw is a tall order. But your best approach is to use a long auxiliary fence. Then choose an already straight or slightly concave edge to place against the fence to true up the opposite edge. As long as the fence is long enough, two points of a concave edge will make contact with the fence and still provide a straight travel path.

Travel at a reasonable speed without stopping or any hesitation, and an accurate edge is possible. Don't forget the importance of a properly set splitter, both for accuracy and safety.

Solid-wood edging

Iron-on edging is certainly an option, but nothing beats solid-wood edging for longevity, wear resistance and beauty. Solid-wood edging allows me to rout a decorative edge on the panels without exposing the plywood core.

It is vital to decide on routed profiles before choosing the size of the solid-wood edging material to ensure it will be wide enough to handle the profile. For example, if you plan to use a Roman ogee profile with a 3/8" distance from the router-bit bearing to the outside of the profile, make the edging at least 7/16" wide, but 1/2" is better. Your edging will, therefore, be 1/2" wide x 13/16" thick. For 3/4"-thick plywood, solid-wood edging should be 13/16" thick to give you something to trim on both sides of the plywood. Most 3/4"-thick plywood you buy is about 1/32" undersized, so that gives you an even wider margin for error.

Glue the edging onto the straight, ripped front edges of all your panels, making sure that the edging stands proud of the panel on both sides. A clamping caul across the front of the narrow edging helps distribute the clamping pressure more evenly. I like to use my Pony #50 pipe clamps for this job, although this is a light-duty job that parallel jaw clamps can handle. Even other medium-strength clamps will do nicely.

For edging that is the same thickness as the plywood panels, glue is sufficient, without any dowels, biscuits or other reinforcements. But for edging that is thicker (top to bottom) than the plywood, more reinforcement helps counteract increased leverage should someone bump into the bottom of the edging. Dowels and biscuits will do, although I find that a continuous spline is quick and easy. You can easily rout a 1/4"-wide x 1/2"-deep spline groove into the front edges of your panels with a slot cutter in a handheld router.

The same groove can be routed in the rear side of the edging material, but don't forget to increase the distance of the groove from the top of the edging so that there is something to trim along the top later. The groove in the edging, which might be something like 11/2" wide at the glue-up stage, can be routed on a router table if you prefer. But the groove in the plywood edge should be routed with a handheld router so that the base follows the mild curves of the plywood faces.

It's important to remember that plywood is rarely flat. Many a woodworker has come to realize this problem with sheet goods. However, placing a curved panel on a flat router table is a sure way to rout a spline groove that rises and falls relative to the top of the panel.

Top grade

Plywood surface materials can vary from high-grade wood veneers to melamine. I use A-1 grade, which is readily available, for fine furniture. The front has A-grade veneers arranged in a flat-sawn, book-matched pattern. The 1-grade back is also high-quality, but will usually have rift-sawn veneers or something just a little less visually appealing.

For less important projects, an A-2 grade might be available, which has a slightly lower-quality back. B-2, which has a lower-quality front as well, could still be adequate for many of your projects. A-4 grade is common for drawer bottoms and cabinet backs, for which only one side is visible.

Cutting dados

Most case goods have some combination of permanent shelves, adjustable shelves and cross-rails, sometimes with vertical dividers as well. From there, you can add drawers, doors, mouldings, and so on to really dress them up. One of the most difficult tasks is making dados to hold the permanent shelves.

If you use a dial caliper to measure the thickness of a sheet of plywood at different points, you might be shocked at the results. It isn't unusual for a sheet to vary by 12- to 20-thousandths of an inch from one end to the other. This distance is about the thickness of one or two standard business cards. Imagine a dado that is two business cards too small-there's no way the shelf will fit. Two business cards too loose isn't much better, unless you use screws or other mechanical fasteners to secure the shelf.

By using a shop-made jig, I can customize the fit of each dado to get a snug fit every time. I use a router instead of a tablesaw for a couple of reasons. First, the jig is easier to adjust to customize the width of each dado, compared with a dado set. Second, I prefer dados that are stopped at the front of the gables. The stops preserve the vertical lines when you look at the front edges of the gables, uninterrupted by the shelf dados. After stopping the dados about 1/2" from the front of the shelves, I notch the corners of the shelves to fit flush to the front edges of the gables. You can do this with the shelves sitting vertically on a cross-cut sled, or pull out that trusty Japanese dozuki saw and practise some hand skills for a change.

The ingenious part of this jig is that I can rout matching dados in both gables at the same time. By placing two gables on the workbench, rear edge to rear edge, the dados are stopped at both ends of a single cut. I use a 1/2"-diameter straight bit to cut the dado, first pressing against the back fence of the jig while travelling from left to right and then pressing against the front fence while continuing from right to left. Two 1/8"-deep passes gives the 1/4"- deep dado I'm after. Before beginning the cut, I can sandwich the actual shelf that goes into that dado between the jig's opening, which sets it to the proper width for a good fit. In this method, I can customize the dados to each and every shelf as I go along.

If you've been working with solid wood for many years and haven't yet tried veneered materials, there is a whole new set of skills to be learned. It is satisfying work to build larger case pieces without having to spend all those hours milling, edge-gluing and levelling massive solid-wood panels.

Before you get too judgmental about using sheet stock, remember that some very fine antiques were made using veneers glued to block-board cores. Had other core materials existed back then, they surely would have been used. Also, veneered materials offer many new options to use parts of wood that can be quite unstable in solid form, such as burls and crotch figures. Open your eyes to all the new possibilities that await you.

Cross cutting plywood

Plywood also needs special precautions when cross cutting. While a combination blade gives the smoothest edge from one core veneer layer to the next, my primary concern with sheet goods is protecting the face veneer. There is no use in spending top dollar for A-1 black cherry ply only to chip the veneers when cross cutting.

While a 60-tooth blade works best for thicker solid wood, plywood beckons for my 80-tooth super-fine cross-cut blade. It leaves the best possible endcut on those delicate face veneers. Keep in mind that zero-clearance protection is required on the underside of the panel, as well as on the front edge (closest to the front of the tablesaw), in order to avoid tearout in those areas. This means you should use a backer board on a mitre gauge and a zero-clearance insert. Better yet, use a cross-cut sled, as it already offers zero-clearance surfaces on the fence and base. I often stack my panels and cut them all at once to ensure they end up the same length, so only the bottom panel requires zero clearance. Panels higher up on the stack already have zero-clearance protection from the panels beneath them.

Iron-on edge banding

An easier option over solid-wood edging is iron-on edge banding, which you can buy from local lumberyards or home-improvement centres. I'm not talking about fake-wood laminates, but real-wood edging that comes in 25' rolls or longer with hot-melt adhesive on the back. Just remember that this kind of edging is only 1/32" thick after application, so the edges of your completed panels must remain square. There is no material thickness there to rout a decorative profile.

Since boards don't generally come 25' or 50' long, rolls of edge banding have finger joints connecting one piece of edging to another to form a long roll. These joints are sometimes difficult to see in the raw, but a stain applied later will easily highlight them. I prefer to cut all the finger joints out of a roll before I begin so that I can see what lengths I have available for different panels in the project. Edge banding is easy to cut with a pair of sharp scissors.

Cut the banding about 1/2" longer than the edge of your panel and apply it with a hot iron set to the cotton setting (quite hot). Keep the iron moving to avoid scorching the wood, but use the other hand to ensure the banding stands proud of the panel on both sides. Immediately after ironing the whole length, press the banding down firmly with a small, flat piece of hardwood. As you slide back and forth, the hot-melt glue will cool quickly to hold the banding on.

Trimming edging materials

To trim iron-on edge banding, I use a regular angle block plane. A chisel will work too, but can do a lot of damage if you aren't careful. Remember that a hand plane is nothing but a chisel holder that regulates depth of cut. One wrong move with a chisel and you're cutting deep into the plywood's face veneers.

For solid-wood edging, you'll be tempted to use a router with a flush-trim bit. Your router has to run on the edge, though, so you'll have to rig up some sort of wider support board next to the plywood in your vise to steady the router. Or you could try placing the edge down on a router table, using a fence to steady the panel vertically.

It never fails, though: a huge chunk of tearout happens at the least convenient moment, perhaps damaging the face veneers at the same time. I prefer to flush off solid-wood edging with hand planes. It may sound crazy, but once you learn to use a hand plane well, it can do a remarkable job at this task. I start with my #4 smoothing plane to get the bulk of the edging close to the face veneers. Then I switch to my regular angle block plane for more control to remove the final .002" to .003" or so. A cambered blade easily keeps the cutting edge off the face veneers, and a 50º effective cutting angle prevents tearout even better than my #4. I achieve this set-up by grinding a 30º bevel angle on the blade, which sits in the plane body at a 20º bedding angle. Keep it sharp and don't forget to go with the grain. Grain reversals will require you to plane in both directions for different parts of the edging-something a router cannot do.

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