Shelf supports with double tenon joints

I needed to build another shelf for the basement. Rather than use the same design as my other shelves, I decided to make some shelf supports using double tenons joints. I figured this application was also a good one to put the strength of double tenon joints to the test.

Usually I round off my tenons to fit in the mortises from my slot mortiser, but for a change, I decided to square out the mortises. These are 3/16" tenons, so 3/16" chisel is perfect for squaring out the ends. The force required was just a bit more than I could easily push by hand, so I ended up using a mallet.

I cut the double tenon using my delta tenon jig. The space between the tenons I cut out by making a series of cuts to remove all the material. I ended up doing the same for the shoulders of the tenon, seeing that these were narrow enough that two passes with the saw blade was enough to remove all that was needed.

Checking the fit of the double tenon. Double tenon joints are a bit more finicky than regular tenon joints, because both tenons, and the distance between them needs to align precisely, rather than just ensuring that the tenon has the right width.

(Update 2009): I have since built my multi slot mortising machine for quickly and accurately cutting multiple mortises, and use my screw advance box joint jig to accurately cut multiple tenons. As such, I don't have to fuss much to get double tenon joints to fit perfectly anymore.

And here's one of the shelf support brackets mounted on the wall. I just screwed them into the sides of the studs on the unfinished side of a wall.

For the shelves themselves, I used some old bi-fold closet doors. These are just strong enough for the job. Not ideal, but I had some lying around, so there was no need to buy anything.

Here you can see the shelves already partially loaded with junk.