Question on splines

[Duane N]

I understand the need for splines on end grain joints to support the glue joint as the grain expands and contracts with humidity changes but is there a "rule" on when they are or aren't needed or is pretty much a good idea to add them?

The box and glue joint in question.  I've never done splines before but I did build a jig for my table saw to cut them.

[attachment=15528]


PS...nothing is glued yet except the box itself.

[hbmcc]

That will look beautiful!

Depending on size or use you may want some. To save the uniformity of the grain you could put splines into the endgrain. Double blind mitered dovetails will work too.

[Stwood_]

Splines, like biscuits, aid with alignment, and add to the surface area for glue.

[Cooler]

As an aside, I find that miters on plywood are pretty strong with just glue.  Because of the alternating directions of the wood, you have both face grain and end grain.   

If you orient the mating boards so that the face grain layers match the face grain layers, you will have 50% end grain glue surface (not so good) and 50% face grain glue surface (excellent).

So a 3/4" thick piece of plywood glued on the miter will have 3/8" face grain and 3/8" end grain glue surfaces, and almost no seasonal movement.  So not a bad joint--or at least not as bad a joint as people have been saying.  

For some projects it is a very good way to construct the piece.

I made a rolling storage coffee table about 20 years ago.  With just glue for all the joints the piece has stood up well.  The corners look finished.  The bottom is glued into a dado all around.  It assembled quickly.  An appropriate construction for this job.

[Joe K1]

Please post pictures after it is finished.  Nice job!

[R Clark]

I would use splines for the piece pictured.

I presume it's for somebody else.  When I send a piece off for somebody else, I always assume they'll put some stress on it somehow and that joints need to be strong.

Better to be safe now to avoid disappointment later.

It would be great if you have some cutoffs of the same thickness so you can do a practice/setup run before you cut on the box pictured.

[jteneyck]

I would use splines on the corners of the box, just make sure the grain runs the same way as the wood it's being glued into.  For the narrow trim at the bottom I use biscuits.  

John

[Duane N]

I would use splines for the piece pictured.

I presume it's for somebody else.  When I send a piece off for somebody else, I always assume they'll put some stress on it somehow and that joints need to be strong.

Better to be safe now to avoid disappointment later.

It would be great if you have some cutoffs of the same thickness so you can do a practice/setup run before you cut on the box pictured.

Actually the box is just an idea I had floating around in my head and started building it to take a break from other projects I'm working on.  I usually end up selling the stuff I make after the fact so I will do splines as suggested by everyone.

[Papa Jim]

I use a lot of splines on my boxes but consider them completely decorative:

[attachment=15553]

[attachment=15554]

[SteveS]

Since you said the box is glued up I assume you mean horizontal splines rather than vertical splines. I've used both for boxes, and none. There is no data out there to indicate at what point splines should be used, but for me, if the sides are rather thin or tall then I feel better adding splines. For short, thick walled boxes I only add splines if I want an artistic aspect included since the gluing surface, even though end grained, is adequate.