Need a tool or method for creating a long miter joint without splines, but still quite strong

[CharleyL]

The OP said that he wanted joints without "Visible" splines. 

I have the Lock Miter bits and Lock Miter Master setup gauges, but I don't care for the tear-out that I get in the lock miter portion of the joint when using them.  The bits might work better if additional cutters were designed in them, but just two cutters creates a lot of tear-out and voids in the joint. Slowing the feed rate helps, but frequently fails to eliminate it.

I much prefer making spline joints like @Shaneymack posted. They are easy to set up correctly when cut on a good table saw,  if you have a good digital blade angle gauge like the Wixey or IGaging units. To get good cross grained splines of the right thickness to match the thicknesses of blade kerf that you cut the spline slots with. I found that using my table saw tenoning jig, set to cut the spline thickness between the jig face and the saw blade allows me to get perfect cross grained splines from each face of each end of a board, or 4 splines at a time. Then Using a length stop on my miter saw allows me to cut them free of the board ends to match the depth of the spline slots the width needed for the joint. If the joint is taller than the spline donor board is wide, more than one spline can be used for each joint, placed end to end in the joint and glued.. Nothing is visible on the exterior of this joint when looking at either the box  corners when looking  either on the inside or outside of the box after the joint is assembled and glued. Cross grained splines like this are extremely strong and I wouldn't hesitate to use this type of joint in plywood or solid wood. In fact, I do use them frequently in both kinds of boxes.

Well made box joints in plywood boxes don't look that bad either, if the plywood is high quality, like Baltic Birch. Attached is a close-up of a box joint that I recently made from Baltic Birch Plywood on several boxes recently.

 

Charley

 

 

[Marmotjr]

Are the interiors going to be used for any purpose?  Or are they just boxes to sit on? 

If they are 'empty' inside, consider putting some false bottoms in them.  Run a 1/4" dado about an inch from the top and bottom of the four vertical pieces, and cut a couple pieces of 1/4" ply to fit.  If you want them lighter, rout out the insides of each insert piece to form a "picture frame".    This will allow you to do a simple miter on the edges, while having something mechanical holding the pieces together. 

[wdwerker]

OP hasn't been online since Saturday afternoon . I'm guessing he's already made a decision . 

[Marmotjr]

23 hours ago, wdwerker said:

OP hasn't been online since Saturday afternoon . I'm guessing he's already made a decision . 

Figured as much, but if it's a good idea, it may help somebody in the future with a similar issue.