Replies

1. 
   Piccioni | Dec 30, 2007 09:02pm | #1

   I'm not as experienced as most folks here, but I have edged maybe 20 plywood counters or tables with hardwood using only yellow glue and have never had a problem with strength so I wouldn't bother with biscuits, spline, etc.. When I subsequently demolished one example I couldn't believe how strong the hardwood was stuck to the plywood.

   The trick is to clamp real good on two dimensions on a real flat surface because any bow, twist, etc. on the edging can kind of warp the plywood.

   You clamp so the top edge of the edging is exactly flush with the top of the plywood because you can't sand the plywood much before you get through the veneer, and its hard to sand the edging without screwing up the plywood. So the trick is, do it right. It goes without saying that both sides have to be flat with no gaps whatsoever, or they'll fill with glue.

   I bought a hugely expensive router bit set from Lee Valley which is supposed to allow you to make a self aligning joint like this, but all I found was that it make the results less predictable than careful clamping.  I suspect a spline would present a similar challenge: at best it would line thing up perfectly, at worst it would force a misalignment however, a glue only joint can be corrected with a mallet when wet

   Use a lot of glue, but remove as much of the squeeze out as possible so a light sanding is all you need afterward.

   Of course, lining up all those miters can be real sporting. I was worried I'd get gaps at the corners from expansion/contraction of the hardwood, but it doesn't seem to happen. Maybe because the plywood is so stable and hardwood is so tightly bound to it.

   Anyhow, I've done this repeatedly in the past and the only challenge I had at the beginning was the top surface alignment.

1. 
   dherzig | Dec 30, 2007 09:47pm | #3

   Perhaps, instead of worrying about the alignment, would you consider making the trim slightly thicker than the ply and trimming it back with a router and trim bit? Then you would have a perfect match without the chance of damage to the ply.

2. 
   Anderson | Dec 30, 2007 09:41pm | #2

   I have done this on several occasions and have had no problems. The plywood is stable and the edging is attached so it's long grain is running along the plywood and there is little dimensional change in length with humidity.

   The way I have been doing it is ... I've a sommerfeld cabinet making kit ... that provides two router bits for a tongue and groove fit between cabinet panels. I use the "groover" to put a groove in the edge of the plywood and I use the "tonguer" to put a tongue on the edging. These fit together quite snuggly and alignment is perfect.

   The tongue is only 1/4" however, so you would not be able to apply a lot of weight on the very edge of deep edging. The leverage would split the ply. You would have the same difficulty with a spline, however.

   The best method would be to build a top with the design you are looking at and put it over a solid piece of ply or MDF of the same size. This would support all areas of the top and make it a lot stronger. You could then apply thin matching edging around the table sandwich and sand/finish it in so it would become invisible.

   Hope this helps.

   Barry in WV

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   Edited 12/30/2007 1:43 pm ET by Anderson

   
   

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   Edited 12/30/2007 1:45 pm ET by Anderson

3. 
   Woodman41 | Dec 30, 2007 11:08pm | #4

   that should be a nice table top, birdseye on cherry is a pretty combination.

   The problem you are going to have, IMO, is that two woods joined in such a fashion leads to a stark transition. Even if you achieve a near perfect joint, the result will still be that the eye focuses on it in an attempt to find the imperfection.

   What I would suggest is something altogether different. Glue up your edges, and I would recommend biscuits, and hand plane or sand everything close. Use a palm router with edge guide to route a shallow 1/8" slot where the edging meets the plywood. Glue in a 1/8" stringing made from something contrasting (my first thought was ash dyed black with some india ink). Use a card scraper to smooth out the stringing to the other surfaces.

   It may sound like a lot of steps but it's really only 3 extra steps, and I think in this case not only will you appreciate the result but any imperfections in the fit will not be noticeable.

   Also, you didn't mention how you were going to finish this piece but you might want to first put on a coat of shellac to seal the wood and prevent any color from bleeding from the cherry to the maple.

   
   

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   Edited 12/30/2007 3:08 pm ET by Woodman41

1. 
   georgep | Dec 31, 2007 12:06am | #5

   Interesting idea abut the inlay.  I may do that.  I was planning on, before glue-up, giving the cherry a coat of shellac to help avoid blotching and staining it.  I'm not sure that makes sense.  If the joint doesn't come staining perfect and I have to sand or scrape, the staining gets messed up.  The inlay would solve any problem with staining after glue-up.

   George

4. 
   douglas2cats | Dec 31, 2007 07:21pm | #6

   The biscuits or spline can help with alignment but it's not really necessary. I typically just put edging on ply with yellow glue applied a hair thick then trimmed flush with a block plane. One other thought here: Go with 5/4 maple and rabbet it out maybe 3/4" x 3/4". It would make the visible edge of the top look thicker plus provide alignment and more glue surface (edge as well as face) as well.

    

   If you build it he will come.

5. 
   Lataxe | Dec 31, 2007 09:07pm | #7

   George,

   I've made a lot of tables and other flat panels using cherry and maple-veneered boards with heavy solid-wood lipping of around the size you quote.  Here is what I found:

   * Hardwood will glue to pywood edges and to blockboard with the block showing long grain, without the need of any helpers.  It won't stick to MDF or to blockboard showing end grain without some form of helper.

   * Biscuits help alignment of panel and the four edges (assuming you use a good joiner with skill).  Watch out for biscuit-swell in weak boards and minimize it by placing the biscuits in the middle, not near one face or the other.  Any swell that does occur goes away once the biscuits/glue dry out. 

   * No 20 biscuits (spaced fairly close together) are generally stronger than a spline.  This seems to be because it is harder to get a well-fitting spline than it is to get well-fitting biscuits. If you can make a very precise spline/groove then use that.  (The spline needs to have the grain across not along its width, though - not easy to make; unless you use thin plywood, which is not necessarily uniform in thickness).

   * Whatever method you use to join the board to the lipping, you might consider enhancing the join wth stringing.  This will add a decorative effect but also obviate any gaps you inadvertently made 'tween board and lip; and also provide a sort of external spline to the join.  I like to use 1/8 -1/4" wide stringing of around 1/8" depth, mitred at the corners. 

   A drum sander makes very precise and uniform stringing but it can also be made with a handplane in a "height" jig.  A downcut spiral router bit used in a router with a fence will make a very precise channel for the stringing when run over the top of the joins (although you can use a scratch-stock, risking the veneer breaking out).  Downcut bits prevent breakout of the crossgrain veneer edge.

   If you don't use stringing then the veneered board can be cut very cleanly (including across the veneer grain) with a TS blade having lots of ATB teeth set at a 45 degree angle.  The very pointy profile makes a clean sheer cut and does not spelch the veneer.  Otherwise (ie using an ordinary blade) you might have to use a TS with a scoring saw to prevent veneer beakout.

   Hope this helps,

   Lataxe