Week 10 – Edgebands

I have mentioned edgebanding in some of my previous posts.  Those were captured edgebands which are glued to the side of a plywood substrate and then veneer is applied to the top and bottom capturing the edgeband.  There are two reasons that we do this at The Krenov School.  First, if this is an exposed edge then a strip of solid wood is definitely finer than looking at the edge of a piece of plywood.  Second, and sometimes debated, is to provide a strip of solid wood that can be more easily hand tooled to a smooth surface and seamless joint.  Try making the edge of a piece of plywood perfectly smooth.  Go ahead, I'll wait.

This week I've been working on the applied edgebands for the top and bottom of the cabinet.  An applied edgeband is a piece of wood that is often glued to the edge of a veneered panel to add profile detail or hide the view of the raw edge which may look like a sandwich of veneers and captured edgeband (or plywood if you don't do the captured edgeband thing).

For this cabinet, the applied edgeband wraps the kidney bean shaped top with  a  strip of wood that swoops up into a spoiler detail at the rear of the cabinet.  The applied edgeband on this cabinet provides the overhang of the top and bottom that visually captures the vertical sides of the cabinet.

The edgeband is about a 1/4 inch thick and is made up of 4 thin strips of wood that are flexible enough to be bent around the profile of the kidney bean.  I divided the edgeband into two parts: the smooth concave curve of the front edge wrapping around the sides of the cabinet, and the rear edge where the curve has both concave and convex sections (i.e. a squiggle).  The two parts of the edgeband are made separately and then applied to the edge of the panel.

The longer edgeband which wraps most of the panel is bent around a large form.  The form made of plywood and routed to match the profile of the top/bottom panel.  The inside of the plywood is removed to make a ring that will allow clamps to be used to apply even pressure to the laminate strips while it is being glued.  In the picture below you can see a few long plywood pieces radiating from the ring.  These pieces are used to align the bottom edge of the strips during glue up.  You can also see a few extra holes drilled into the form around the tight radius corners that allows me to double up on clamps as the strips bend around that curve.  After making up the thin strips of wood, I apply some Unibond 800 glue and wrap the strips around the form along with a bending caul made from cardboard and veneer and other bendy things.  And then I use a few clamps to apply even pressure along the entire length of the edgeband.

After the glue cures, I remove the clamps and clean up the edgeband surfaces.  I made a sample edgeband from poplar, which is shown below, to test out the form and the process.  Jumping ahead a bit, you can also see the prototype spoiler that will be mated to the edgeband that will complete the applied edgeband for the panel.

I need to make sure that the ends of the edgeband have miters that are perfectly smooth and square so that the edgeband/spoiler at the rear of the panel can mate seamlessly.  After sawing the end of the edgeband to the proper length and approximate angle I use my shooting board with a wedge to hold the curve at the proper angle (along with some blue tape) to plane the end of the edgeband square and smooth.

The final step is to glue the edgeband to the panel without any gaps or glue lines.  This turned out to be much more difficult than I had predicted.  After a day or two of trying to find a clamping scheme that produced the desired results and chasing down the tiniest imperfections that I had introduced on the inside edge of the edgeband and outside edge of the panels, I came up with a solution that seemed to work consistently.  First I wrapped the edge band and panel with one of the most powerful strap clamps that I had ever seen.  Second I encased the entire setup with a set of hard cauls and bar clamps.  Finally, by tightening the bar clamps in the right order I could slowly move the pressure around the panel closing the gap along the way until I ended up with a seamless joint.

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