Getting the Edge: Plywood Edge TreatmentsComments (0)
This article is from Issue 19 of Woodcraft Magazine.
By Craig Bentzley
Solid Advice For Plywood Edge Treatments
Regardless of the plywood product you elect to use for your project, one thing is certain; you will want to apply a facing to exposed edges.
W ith the costs of solid lumber rising and the availability of wider stock waning, hardwood veneer plywood has become the material of choice for built-ins, cabinets, and case goods. Many cabinetmakers lament that the quality of veneer core plywood has declined over the past decade. As a result of this, more and more professional shops are switching to MDF (medium density fiberboard) core plywood as their standard because it provides a flatter and smoother substrate for the face veneer. The options are myriad and as with everything, there are pros, cons, and trade-offs for each method. In order to make an intelligent decision about your choice of edge treatment, you’ll need to evaluate the use or abuse that the finished product will see, the environment that the product will be in, what tools you have available, and how much time you want to invest. Sometimes you may even want to combine different edge treatments in one project.
In a nutshell we’ll just say that there are only two types of edge treatments for plywood—veneer and solid wood—so let’s start with the easiest method first.
Iron-On Veneer Edge Banding
The most common treatment for raw plywood edges among beginners is veneer edge-banding tape. It is available in a wide variety of wood species and has a heat-sensitive adhesive applied to one side. It is typically 7/8" wide to allow for trimming and comes in rolls from 25' to 250' long. Although many specialty tools are available if you plan to do a lot of edge banding, the job can be accomplished quite handily with tools you probably already have.
To apply veneer edge banding you can use an edge-banding iron designed specifically for the job or a simple household iron set on medium heat. Cut your strips about 1" longer than you need, hold in place, start at one end, and apply moderate pressure with your iron along the length of the edge. If you go too slowly you risk scorching the veneer and if you go too fast, you won’t completely melt the adhesive, which will result in a poor bond. Quickly follow up with heavy, even pressure from a hand-held rubber roller, being careful not to go over the ends, which will break off the over-hanging veneer. Allow this to cool down before trimming or you’ll end up with a sticky mess on your trimming tools.
Trimming can be done with a sharp chisel, a block plane, or any number of specially designed trimmers (see photo) that are widely available. The extra length can be cut off with a chisel or an end trimmer. After checking for any adhesive residue that may be left, all that’s needed is a light sanding before applying a finish to your workpieces.
It may be fast and easy to apply, but veneer edge banding does have its downsides. First of all, it’s not heat resistant so it’s not a good choice for an item that would be located near an oven or other heat source. Secondly, it doesn’t hold up well to a lot of use so you wouldn’t want to use it on the edge of a table, for example.
Solid Edge Treatments
A simple solid edge strip is just a little more work than iron-on edge banding and is a lot more durable. Use wide stock that is about 1/8" thicker than the thickness of your panel to allow for trimming. Joint the edge, and then set up your rip fence to cut the desired thickness of your strip. Rip your edge strip, joint the edge of your board, rip another strip, and so on, until you have the required number of strips.
To attach the strip to your panel, apply glue to the edge of the plywood and put the jointed side of the strip onto the panel. You could use clamps but strips of strapping tape spaced a couple of inches apart along the length of the panel work well to hold the strip in place until the glue dries. A few brads will also hold the strip in place; just be sure to sink them deep enough so that you won’t hit them with your jointer or plane when you finish the edge.
When the glue is dry, you can flush up the edges with a plane, a hand-held router with a flush-trimming bit, or you can make something similar to my foolproof router table fence (see photo at bottom) to trim off the excess.
Most cabinet shops consider “V”-shaped edging to be their premium edging technique. It is strong, and almost invisible if the grain of the edging material is carefully selected to match the plywood panel. This joint can be made on a table saw but the setup is fussy and time-consuming. With the introduction of dedicated router bit sets, the procedure is a snap. It provides all of the benefits of tongue-and-groove treatments and can be set up faster. (See the Buying Guide below for a set.)
Variations on a Theme
Biscuits make the job of attaching a heavy edge strip quick and easy.
Pocket Screws are another fast method for attaching a heavy edge strip. If you plan to put a profile on the edge, make sure you won’t hit the screws with your router bit.
Tongue and groove
There are three variations of tongue-and-groove treatments, all of which are super-strong. Although they appear similar, each one has its own advantages and disadvantages. The tongues and grooves of all variations can be made in two ways. One is on the table saw with a dado set and the other is on the router table with a slot cutter or a matched tongue-and-groove bit set. Either way, set-up is tricky and test cuts on scrap are advised. It is always easier to cut the groove first and fine-tune the tongue to fit.
The “T” type molding or grooved panel (see photo to the left) is a good choice when the edge needs to be profiled. As you might suspect, the other variation has the edging grooved and the tongue on the panel. Both methods require the same basic setups, just reversed.
The third variant has the panel and edging grooved and a spline is substituted for the tongue (see photo to the left). The spline can be made from solid wood or ¼" plywood. The benefit of this method is that the setup time is much quicker because you only have to make sure that the slot width matches your spline stock. If the groove is not perfectly centered, it doesn’t really matter because you cut the panel and the edging using the same setup.
Tips for solid Edging
Here are some general tips for applying all types of solid edging:
1. Make test cuts on scrap before committing to your project.
2. Apply a strip of blue masking tape to the edges of your panel before applying glue and cleanup will be much easier.
3. A flush cutting bit properly set up in a router table may still not cut perfectly flush edges. Use a sharp, well-tuned block plane to make your edges perfect.
4. If you’re applying edging to pairs of panels, you can reduce the number of clamps you need by using the panels as cauls. Put glue on the plywood panel edges, apply the edging, then position the panels so the edging strips are face-to-face and clamp across both panels.
5. Make your panels slightly oversized in width and rip to finished width after trimming and cleaning up the edging.
6. Combining tips 4 and 5, you can make edging for two shelves in one solid piece, glue the panels on both sides, and rip down the middle to produce two shelves.
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