Yet another shelf build

The previous occupants of our new house left behind these shelves, which are very wobbly. I guess they are meant to be screwed to the wall to make them safe. I didn't want to do that, so I figured I'd use some of the materials from these to make something more to my liking and sturdier.

I could have built something like these ones, but I don't like building the same thing twice.

Taking the old ones apart. A 1/2" nut driver in a cordless drill made quick work.

I figured I might as well re-use the actual shelf platforms of these, but I didn't want to attach them with bolts like they were (that would just end up wobbly). The boards of the platform overhang the support just a bit on either end, so I figured if I screwed the supports to the side of the shelf frame, that would work.

And a bunch of short 2x4s cut in half will be the horizontal supports, here cutting these to length with a table saw sled.

The frames for the shelves will be a bunch of "ladders" like the one shown at right. I'm joining these together with double mortise and tenon joints.

Marking where the horizontal rungs will go. First I measured them, then marked across several pieces with a square.

Two 1/4" mortises, spaced 13/16" apart (6 mm mortises spaced 20.6 mm). Inches are awful, but with the mortiser's vertical adjustment threaded rod in inches and the router bits in inches, it makes sense to put things on even 16'ths of an inch.

Some of the mortises. I cut a total of 80 mortises for these shelves (I made five ladders - two more for another shelf)

Then switching to the pantorouter to cut the tenons. I could have cut the mortises with the pantorouter as well, but I like to cut these on separate machines so I can go back and forth between the two joints without having to change the setup.

The first tenons I cut were a tight fit in the mortises. A bit too tight for assembling with glue.

But with a tapered follower, and a tapered template, I just need to back the follower up slightly to cut the tenons a bit smaller.

Having tested the fit with the tenon still mounted in the machine, I just need to make another pass around the edges of the tenons to try the adjusted tenon size.

I rounded the edges of all the horizontal pieces on my belt sander, and used my palm plane to chamfer the edges of the vertical pieces.

Assembling the ladder. I apply glue to the mortises with a splint of wood, dipping it in a yogurt cup full of glue.

Adding the second vertical is more tricky, with four joints (8 tenons) that need to be lined up.

Three frames done (I made two more for another narrower shelf in addition to those three)

Testing one of the ladders against racking. I clamped it to the side of my big scaffold and climbed up the other side. Those double mortise and tenon joints can hold a lot of load!

Then back to the basement to assemble the shelves. Here screwing in one of the shelf platforms.

I had extra shelf platforms which I cut into two board wide sections to add next to the three board wide sections.

As built, this shelf doesn't have a lot of stiffness against side-to-side racking, so I added a diagonal member to both sides to stiffen it up.

And, once loaded up with heavy stuff, testing against front-to-back racking. Also no problem.