Dressing up curved plywood edges

[Greg Guarino]

My CD Shelf project is drawing to a close. All that's left is a couple more bouts of finishing, and only on the face frame and the outside faces of the sides. It should be ready for use next weekend. Here it is:

I've begun to think about what I might do next. The bookcases I built two projects ago now hold virtually all of the books in the house, excepting the cookbooks, which we'd like to keep in the kitchen. Here's my completely half-assed idea:

Pretend I've drawn it with dadoes and rabbets, and pretend that the "mezzanine" shelves follow the curve of the top and bottom. Further pretend that this design bears any resemblance to what I'll really build.

What I'm curious about is how to deal with the plywood edges if I decide to build a curved unit. We have a lot of cookbooks, some small and utilitarian, others large and full of pictures. I figure the curve will help accommodate both deep and shallow books, and hopefully look nice in the process.

I used iron-on edge banding for the CD shelves, which worked out pretty well. But if I wonder if there's some solid wood alternative. Keep in mind that milling my own strips is not a possibility. I think I've seen rectangular profile molding and I'm sure I could just look up what's available But I have gotten some ideas from this group in the past; ideas I never would have thought of. So have at it. Things simple enough to match my modest skills preferred.

[Ed Pawlowski]

You say milling is not a possibility. What tools do you have available? Router? Router table?

In pine, there is some molding available at the big box stores, but not so easy to find other woods.

What I would do is run a board through the router table putting on the profile of my choice. Then I'd cut it off on the table saw thin enough to bend around the shelf edge. Repeat as necessary to get enough material for the job.

[Greg Guarino]

Router? Check. Router table? Ditto. But no table saw.

[Swingman]

On 12/30/2013 9:43 AM, Greg Guarino wrote: iron-on edge banding for the CD shelves, which worked out pretty

DAGS "flexible trim"

[Swingman]

A few years ago I built a jig, based on an old magazine article, for a router/router table to do this:

The perfect match of the mating parts (table top and trim) comes from using the jig to cut the curve in both parts.

If you're interested I can try to find my plans/send you the directions necessary to do the same via email, or a photo of the jig, which I may still have (if I can find it).

[Greg Guarino]

I don't know if I would actually take that route - cutting the curved pieces from 1x4 stock - but I'm intrigued. I've been puzzling it out in my head and I haven't yet come up with the geometry necessary to make convex and concave cuts from the same template. Obviously it's not as simple as a pattern bit; the non-zero diameter of the bit would make the mating curves of slightly different radii.

So don't dig too hard on my account, but I am interested to see how it was done.

[dadiOH]

You said you have a router & router table but no table saw. How do you cut the ply pieces? How did you cut the stuff for the other book case?

Regardless of how you did it (cut) do it the same way for this project. You could...

1. Cut thin pieces and glue/iron on
2. Cut thicker pieces and bend them on, no need to cut a curve as long as they are 3/4" thick or so. To attach them, you could... (a) use biscuits & glue (b) put solid wood vertical at the front of each side and screw/glue to that, glue to the ply too.

Naturally, you could run a profile on one or both edges.

1. Now, if you want something wide you would either have to... (a) cut a curve to match the ply - OR - (b) make the ply uncurved and curve the outside edge of the solid wood.

It's not all that hard to cut a curve with a router, just need to make a template. If you want the innner and outer curves to match so the trim is the same width over the entire length, pay attention to Swingman.

[Greg Guarino]

Circular saw with either this:

this

or this

... depending on the length of the piece to be cut.

I also use a miter saw for narrow stuff.

[Digger]

There are special edging bits for routers that can be used to enhance glue-up of stock trim ...i.e...

The cutters ensure sufficient gluing surface for a very strong bond between case and edging.

After edging is glued on, then molding or profile bits may be utilized with the same router to clean up any proud surfaces and apply final desired shape ...roundover, roman ogee etc.

Not easy to work with thin sticks of 3/4" stock without using some sort of backing board (i.e. 3/4" x 1"x4" scrap stock) or support to provide added stiffness and bulk while routing the glue edge. I have used double-sided carpet tape to temporarily hold things together while cutting, and it is entirely possible to also tape the edge stock either edge-to-edge or on top of backing board. However, I also prefer routing from thicker stock and subsequently cut strips to final dimension with a table saw.

Once the stock edging is mounted to the case, it is usually very easy to profile the exposed edge surface with a molding bit of choice.

Hope my explanation makes some sense, I'm at an age now where most of the time I'm the only one that understands what I write...

good luck,

[Greg Guarino]

I thought of that too. I'm trying to decide if I'd like the look.

[-MIKE-]

The inherent flaw in those bits is that it is way too easy for the pointed edge of the hardwood to split open the plywood when clamping.

If one chooses to use an edge banding router bit, it's much better to use a bit that has a flat section, so it can't wedge open the plywood.

After trying router bits for banding, I came to the conclusion that their best purpose is to provide income to the people who manufacture and sell them. :-)

A simple rabbeted banding that is thicker than the plywood is as strong or stronger than these special profiles and much easier to do. Plus it give the added advantage of making the front profile thicker, which looks better in most applications.

[DanG]

If someone else has said this, I apologize. You can use MDO - medium densidty overlay - same thing as MDF with various hardwood exterior veneer finishes. This would allow you cut, rout, and finish. This assumes you are bent on a wood finish. Straight MDF for a stellar paint finish.

[Digger]

Agreed.

The point was simply that there are bits of many flavors, as in the example indicated (i.e.), that can be used with a router to increase the surface area for glue up and add strength to the joint. The added advantage of course is that the trim interlocks with the casing and thus keeps the edging centered while curing.

Your rabbited method is excellent and the normally preferred alternative, assuming one is not looking for edging that is flush on both faces. Simplicity + added strength is indeed the primary goal and the rabbit also assures accurate alignment. However, in a curved applique it may also be considerably more difficult, if not impossible, to apply to a contoured edge. But then, in extreme situations, banding with tongue and groove method would not work either.

Whenever possible, for fully flushed edges, I personally prefer biscuits above all, but in many situations the edge band is entirely to thin to support this method.

So, in essence, the method used is largely dictated by design, tools available, and desired outcome. This only goes to show that once again, there is indeed more than one way to skin the proverbial cat ...uh oh, cat lovers everywhere will now hound me to death!

Speaking from my own experience though, I've never had an occasion where casing walls blew-out or split while clamping tongue & groove, but that is only my own experience. Most of what I build these days is fairly limited to simple hardshell cases for instruments & audio road gear, wherein the rabbited method would certainly not be appropriate.

Good reply Mike,

[Sonny]

Is using ply a cost factor or expansion/contration factor? Compare the cost of using solid wood, rather than ply, for top and bottom.

Why not use solid wood for the top & bottom, then rout any profile or curved edge you want? Profile: Match what's presently existing in the kitchen's other woodwork?

Sonny

[Mike M]

You could always by a veneer that was thin enough to cut with a straight edge and razor knife.

Mike M