Hardwood edging to ply?

[Brian Penning]

Does hardwood(walnut in this case) usually secure well with glue to good quality veneered plywood?
Was pondering this upon noticing the the 3/4 ply had 3 layers with the grain and 3 endgrain layers

[Zach England]

This would be a better (albeit more expensive) solution:

http://www.eagleamerica.com/product/...2/best_sellers

[John Thompson]

As Zach noted... I would spline it in some manner.

[sean m. titmas]

I use 1/4" splines and a 1/4" bit in the router table to mill up the plywood and edging. i also use a Collins plywood prep bit to dish out the plywood edge and make the joint line near to invisible as possible.

first i rout the 1/4" slot than rout the Collins bit. glue and clamp the entire assembly than after it dries i flush trim the top edge of the solid wood edging. i keep the lip on the bottom.

[Matthew Hills]

Does hardwood(walnut in this case) usually secure well with glue to good quality veneered plywood?
Was pondering this upon noticing the the 3/4 ply had 3 layers with the grain and 3 endgrain layers

I've done this for shelves with oak and birch on their respective plywoods (with veneer core plywood). I either use cauls and clamps to hold it on during curing, or even just use blue masking tape. Both have worked fine, and I haven't had any problems with the trim coming undone. Unless you have major voids or the piece will end up in an abusive situation (school desk), it should probably work fine.

Matt

[Howard Acheson]

You can glue solid hardwood directly to the edges of multiply ply wood without reinforcement. The adhesive will hold just fine. However, some like to use biscuits for alignment purposes

[Byron Trantham]

I just glue them using clamps. A couple years ago I ended up with a piece about 1' long so I put it in the vice and tried to knock off the trim from the plywood. It did come off but it wasn't a glue failure. The solid wood (oak) and some of the plwood let loose! I haven't considred anything else since.

[Philip Rodriquez]

I like to make my own banding using 1/8" to 3/16" strips of hardwood. I only use the larger pieces if I need some extra support.

[Rod Sheridan]

I simply glue it to the plywood edge.........Rod.

[John Harden]

I just glue it on. No biscuits, splines, or other reinforcement is needed IMHO. Recently glued some on table leaves that are veneer over BB ply.

Hardwood edging goes on first, then the veneer goes over the top. Works just fine.

Regards,

John

[Doug Shepard]

This is one of the rare cases where I usually side with Norms brad-nailer approach to everything. Clamping works fine, but why bother? A few brads will hold it tight until glue dries. Then drive them in with a nail set and add a drop of finishing putty later and no one's the wiser.

[glenn bradley]

Like Howard, Rod and others; I just PVA glue it on. I have such constructions in offices and homes - no failures.

[sean m. titmas]

I agree that a spline on all but the most heavy duty of loads is overkill. the reason for the spline is to align the edging to the plywood with a consistent reveal. the reason for the spline is not for the added strength but for precise alignment during the glue up. even though there is an extra step with running the dado i find that it makes the glue up go much faster and its always dead accurate. once i lay it all out i have the shop Probie glue it up with no problems.

[Brent Leonard]

On tabletops where someone who moves the piece may grasp the top around the edges to lift it, I go through the extra work to route/cut a groove on both plywood and edging for a full length spline of ply or hardboard.

I believe a full length spline does add strength as it adds considerable more glue surface to edge & face grain within the ply.

If the piece will not be lifted by the edges, no need for the extra step. Just glue and pin with airgun.

[Howard Acheson]

Let me see if I can explain why a splined edge joint is, in fact, weaker than any other edge to edge joint. Keep in mind that a well fitted and glued edge to edge joint using a modern glue is stronger than the wood itself. In other words, a cured, glued edge to edge joint will not pull or break apart at the joint itself, it will break somewhere else. Adding a spine, biscuits or dowels does not change this. Strength has to do with the wood, not the joint. Also glue joint router or shaper bits are used for alignment, not because it "adds gluing surface" and therefore produces a stronger joint.

So, back to the spline weakening the joint. When you use a spline, you first cut slots in the edge of both boards. Let's assume the slot is 1" deep on each edge. If you tried to use a 2" wide spline, applied glue and attempted to clamp the joint it would not close because the glue that accumulates at the bottom of the slot prevents the spline from fully seating. To deal with this the spline must be cut somewhat less wide than the combined depth of the slots--say 1 3/4". Now the glue has somewhere to go but the spline no longer bottoms in one or both slots. This open space in the bottom of the slot now has no wood (or strength) in it and it is now a weakened area in the wood. When pressure is applied to the panel, it will ALWAYS break along the bottom of one of slots. So, while the glueline joint itself will not fail, the strength of the overall panel has been compromised by this/these areas that contain less wood. And, these areas run the full length of the panel.

Some might argue that if the splines where accurately sized to allow them to bottom fully, then there would be no loss in strength. In theory, this is correct but from a practical point of view the excess glue still needs to go somewhere and glue itself has little strength. If you used epoxy glue which has some gap filling properties, then the area from the edge of the spline to the bottom of the slot would be as strong as solid wood.

The point is that "strengthening the joint" is not what biscuits, dowels or splines do when edge to edge gluing. They strengthen the wood on either side of the joint therefore the breaking point will be beyond the area supported by the reinforcement.

In summary, using the standard woodworking adhesives in a properly prepared joint will give you a glueline that will not fail. The wood may fail along side of it but using other reinforcement just changes the location of the failure to some other point. Use biscuits, dowels, glue joint router bits and splines for alignment, not for strength in solid wood edge to edge joints.