EngiNerd Designs

I put together a couple test joints to make myself feel better (or worse) about a wall mounted bookshelf I’m building. Before this test, I was thinking I would for sure need to reinforce the miter joints. Now I’m not sure if I will. I think both samples were plenty strong for my application.

Notes:
- Wood is 0.75” x 2” white oak
- Glue used was Titebond 3
- I extended the moment arm to 24” so I could break the joint with a reasonable force. Does it make sense to measure joint capacity in ft-lbs? If so both took 70-75 ft-lbs.
- For each glue up, I let the glue soak into the end grain and get tacky for a few minutes, then applied more glue before clamping. I’ve read this helps with end grain joints.

Some additional thoughts/comments:
- To make the splines, I used the biscuit jointer hack to cut the slot. This leaves a rounded void at the bottom of the spline, but not enough to seem like a big deal. This method did limit the depth of the spline in the joint. If I had a table saw jig, I would make the splines deeper, which I think would help.
- Both joints failed at the glue, which surprised me. Often, you get some wood breakage during joint destruction tests. I only let the glue cure for about 24 hrs, so maybe that’s a factor.

Feel free to comment with any more thoughts, critiques, or if you want to see more destruction tests. This was pretty fun, so I don’t mind an excuse to do more.