Last night I finished the shell of the tool cabinet that will go under my workbench. When done, it will resemble this:
The tool cabinet was designed to be an integral part of the bench - to add structural rigidity resisting back-to-front racking (the end panels screwed to the insides of the legs) and side-to-side racking under heavy planing, via a solid center panel stretching the length of the cabinet. The bench has turned out to be quite solid without the cabinet, but I decided to follow through with this design anyway. A bench can never be TOO rigid, right?
This does add a challenge in the build process, since the cabinet needs to fit perfectly (very snugly) between the legs in order to augment the structural rigidity. What are the odds I can build a cabinet that would fit in that perfectly? Not very good. Even if I could, the right fit would be nearly impossible to slide into place. If it could slide in, then it's not a tight enough fit. So I decided to build the cabinet in the bench, rather than assembling it outside and then installing it. I started by screwing down the bottom panel (which just barely slides in between the legs) to the stretchers. Note that all the panels are 3" oak frames with stub tenons and 5/8" MDF panels. MDF was selected for price, stability and weight.
Next, the sides were glued to the bottom panel, clamped down and then clamped and screwed to the legs:
The center panel presented a bit of a challenge. Ideally, I want the panel just a tiny bit oversized, pushing out against the sides and therefore preventing any racking along the long axis of the bench. But that panel would be very hard to install without damage...and how to glue it? So I decided to use two panels that could then be "unfolded" into place, for lack of a better term. I started by clamping four stops to the sides and bottom panel of the cabinet to help align the edges of center panels. The four little scraps on the base will allow me to get the center placed in the X/Y plane and then drop it down (Z plane) onto a glue line in the next step
Here I've added a line of glue where the center panel will sit on the bottom panel. Also, each end of the two center panels have glue. When I unfold them in place, these glue lines will glue the center panel to the sides and to each other.
Here I have the panels with the outer edges in place. When I push the center edges into place, they will come together to form a single center panel. Then I'll remove the shims and gently pound the center panels down onto the glue line on the bottom panel.
They came together perfectly. I put the top in place temporarily so I can clamp down the center panel solidly onto the bottom.
I hope that the explanation was clear. I've never assembled anything in this manner, but the result is an absolutely perfect fit. I could not possibly remove this cabinet without dis-assembling the bench. There is presently nothing but glue holding the sides/top/bottom/center together. If I ever decide to disassemble and move the bench, I hope I remember to put some screws in it...I'm not sure how good the glue joints are. I have no reason to believe they're less than perfect, but it'll never be tested as long as the bench is assembled.
I could not detect any flex in the bench before, even under heavy planing. But I suspect an independent observer would be required to detect small amounts of flex. Or a camera (hmmm...I should try that!). The cabinet now forms what is essentially a big fat wooden I-beam down the long axis of the bench, so if there is any sway in this bench at all, I'll be dumbfounded.
I've been weighing the bench components as I've assembled it. With the cabinet shell complete, the bench currently weighs in at 268 lbs! I can still slide it around, but barely. I suspect that I need to decide where I want it before install drawers full of tools or I may not be able to move it again!
After a light coat of oil, here it is from the front and back...ready for drawers and shelves. I've only built a handful of drawers in my woodworking life...I'm planning at least 11 for the cabinet...maybe more. I expect to screw up a good bunch of them, so figure 15 or so, in total.