Need to guide a very wide mortise

[phi1l]

Or .. if you don't like the joints showing from adding cleats, you could just take a second piece of ply, 19x19, & cut out an 18x18 hole in the middle & glue on the resulting rim.

You may be sensing that experience suggests that routing out that large of an area is a really big task & there is a realy possibility that you won't be satisfied with the results.

[SARGE..g-47]

If you could live with a 1/4" recess you could cut a hole in another piece of 1/4" ply and simply glue that piece with hole on top of the solid bottom piece so you have the finish ply showing on both. Or you could use 1/4" bottom and miter ply strips on top.

I want question why you are not going to band the outer edges with soild wood to hide the ply layers. I will mention it is very easy to do so by splining the edges for a female reciever slot in the ply and and rabbet two sides of solid wood for the male connector in the band. It would give a much more refined look but... if you like the looks of ply edges.... you like the looks of ply edges and that translates to personal taste.

Good luck...

[JoeyGee]

Granted, the area isn't too deep, but that's a lot of wear and resin buildup on your bits, too.

To me, the other options presented seem much easier to me. I would either cut a 19x19 square and add the pieces to the edge, or as phil suggested, cut a "rim" of the ply you want and add the 18x18 middle.

[WestofLongBeach]

Sarge,

If you could live with a 1/4" recess you could cut a hole in another piece of 1/4" ply and simply glue that piece with hole on top of the solid bottom piece so you have the finish ply showing on both. Or you could use 1/4" bottom and miter ply strips on top.

I want question why you are not going to band the outer edges with soild wood to hide the ply layers. I will mention it is very easy to do so by splining the edges for a female reciever slot in the ply and and rabbet two sides of solid wood for the male connector in the band. It would give a much more refined look but... if you like the looks of ply edges.... you like the looks of ply edges and that translates to personal taste.

Good luck...

Of course, ordinarily the ply wouldn't be much decorative, and this is an experiment. In fact, I don't usually want to use plywood at all.

But the notion I have is to use a quarter-inch or so roundover on the upper outer edges, and finish it clear. I want to let the material make the statement for the edge, rather than covering it. If I am successful (it is a gameboard swivel) the graphics of the edges will complement the graphics of the games themselves, that tend to have repeating, parallel lines. We'll see.

[WestofLongBeach]

For best results and the best look on the edges, I suggest using Baltic birch plywood, no matter how you do it.

Loring makes good points about what routing this big recess will expose in the inner plies. It won't be pretty, and you're almost certain to get a lot of splintering and burning from the glue.

To ease the workload and get the desired look on the edges, you could cut the 18" square opening all the way through a piece of 1/8" Baltic birch plywood, then laminate that to a piece of 3/8" Baltic birch. (If the ply structures of the two different thicknesses resulted in an unbalanced look on the edges that you would find objectionable, you could use three pieces: 1/8" top layer with the hole, 1/4" middle layer with no hole, 1/8" bottom layer with no hole.) Cut the pieces oversize and glue them together; then cut the piece down to the final 19" x 19' size.

LarryG,

I have a piece of baltic birch ply. I agree with you.

If the area being worked results in the downsides mentioned, i.e. glue buildup and wear on the (3/4") bit, then that's something I hadn't thought of. I may end up paying a price, here, that I was too la, la, la to anticipate.

And if the area comes out less than attractive, I may have to paint the recess, to cover up my lack of preplanning.

I have decided this: I can rout each edge of the recessed area, by setting up a fence exactly the right distance from my piece so that running the router along the fence will give me a good, straight line, and do this on all four sides. "Floating" the router, it was called by someone. And once all the sides are cut, try to float the rest, except maybe for the last six or so inches at the end, where I may have to use the strips others suggested. But probably I can float the whole thing by simply starting at one pre-cut edge and continuing to its opposite.

Whew.

Don.

[WestofLongBeach]

Well, I finished "gouging" out a recess, and a fairly level one in the birch ply I had. Probably better than I deserve.

I'm surprised by two things:

1. Although I was pretty sure it could have looked mighty grisly, with lots of glue and much less attractive material showing through, it looks pretty good. Not as level as I'd have preferred, but a vibrator sander will get that done. I seem to have 100% wood at the level I cut to.

2. Routing it took longer than I thought it would, about 1/2 hour with a Ryobi 3/4" bit, for the scant 3/32" depth I decided on. It was more difficult than I had thought to hold the router level on just a shelf of "land". Who is surprised other than me?

Lessons learned: I bet if I could have fashioned a 3/32" sub-sub base for the "trailing half" of the base, it would have worked that much better. Next time.

I have some photos I will post this weekend. It isn't done, but the lion's share of the work is behind me, I think. "Major combat operations have ceased."

All your advice, commentary and misgivings got me to focus on some issues I hadn't thought of, and I think the machine is going to be attractive, and she'll like it.

Thanks, all. This isn't the end, but thanks, anyway.

Don.

[cabinetman]

When you have a project where several methods may work, you did the right thing in considering all the ways to do it. Sometimes the best method may not be the easiest.

If you like the "layered" look for the edge, gluing up a length of contrasting hardwood layers (light and dark woods) to create the "layered" look, and just add to the edge (like a moulding). It would machine and finish much nicer than plywood.
.

[os1kne]

I'm curious to see the result. I'll be honest and say that I thought that routing through the good face layer of plywood to expose a large section of an interior ply would not look good. (I don't think that I'd do it with anything but good quality BB ply - definitely not the stuff from HD or Lowes.) But, I'm glad that you tried it and are happy. Personally, I think that the edges of a good quality BB ply look decent on normal-use items.

[WestofLongBeach]

Ok, here goes with the interim pictures. From an elderly Treo, so not so clear. And, BTW, this is NOT your father's, nor anybody's, birch ply. It is in fact a bright white-colored pine that I found attractive, with a nifty grain. Apologies for the mistake, but it really appealed to me and, oddly, got the project going, see below. N E way.

The first is partway through. The second shows the sort of "beach at low tide" effect achieved by not being able to hold the router absolutely level.

Obviously in progress. But I DID get a nice, wood "groove" (as contrasted with what I call the "land", the surface as manufactured) which I probably can smooth.

Now. As for the choice of materials. Certainly the comments of cabinetman are apt. But.

Ply worked for the application, as laminating would have. Laminating would have been better, but I have not taken on anything like that, and when I saw the sheet of pine at HD, I thought it was what I wanted, with no thought for possible failures.

It, in fact, gave me the idea to do what I ended up doing. I think materials sometimes are supposed to do that, though for me, the idea that plywood might "speak to me" is foreign. Normally don't like the stuff. Sometimes if you follow that sort of notion, the results will be really, really comical in my experience, but what the heck.

I was also attracted by what I thought would be rigidity of plywood, and lightness in conjunction with that rigidity, as the giftee is a young woman (see my second post, it's my DAUGHTER!) who likes things light and polite, and to appeal to her, I had to take her tastes into account. As it happens, it is quite light and rigid as you see it in the last picture.

Don.

[AlanWS]

I think the easiest sequence for doing the routing you intend while retianing stability would be to first cut around the edge using an edge guide, as you have done. Then reset the edge guide, and make passes parallel to one edge, but further from that edge. Keep cutting out stripes, but leave narrow ridges close enough to one another to support your router, keeping it from tipping. Once you have nothing but narrow ridges remaining, attach a couple of shims to the bottom of your router, then with the shims straddled over each ridge resting on the recessed surface, take off the ridges.

[WestofLongBeach]

AlanWS,

I think that's a really good suggestion. Next time I get myself into this particular fix, I'm going to take it. And it could actually happen, so thanks.

Don.

[sscherin]

I was thinking the easy way would be to get a 1/8" square of ply.. cut the center out and laminate it to the base ply.. Run around the outside with a laminate trim bit or round over and it'll blend right in. It's all ply so it will look like it's just another layer and you'll have a nice face layer inside the recessed area. Though I'd be inclined to make the recess an extra 1/16th deep and lay down felt or leather inside..

[WestofLongBeach]

I was thinking the easy way would be to get a 1/8" square of ply.. cut the center out and laminate it to the base ply.. Run around the outside with a laminate trim bit or round over and it'll blend right in. It's all ply so it will look like it's just another layer and you'll have a nice face layer inside the recessed area. Though I'd be inclined to make the recess an extra 1/16th deep and lay down felt or leather inside..

sscherin,

Hah! Good suggestion with the felt or leather. Wasn't my vision, but sounds pretty good.

As it turned out, whatever layer was 3/32" down looked pretty good, IMO.

Don.