Thinking ahead to winter projects, I plan to spend some of the rest of the day in the CAD program, laying out a sandblast cabinet I want to build. Thinking 5' long x 3' deep x 3' high. I may have most of the angle for it already, just need the sheet metal. Can use the gun/hose from my Sears sandblaster and probably use the Shopvac with a HEPA cartridge to filter the air. Glass and gaskets for the window is available from TP Tools over in Youngstown, along with other accessories.
Keep in mind you can only blast what you can reach with the nozzle, so even though something might fit in the box, if you can't reach it, it might as well not be in there at all. You can get around that by installing more glove ports, more than two along each side is a possibility, but that means more viewing ports as well. $$$ Take some time to figure out what you want to blast, then tailor the box size accordingly. You can temporarily tape a plastic garbage bag over the door to contain the dust when doing things that won't fit in the box, but it's a PITA to break the tape seal to flip whatever you're blasting around to do the other side. But doing so expands the capability of your setup for almost no money. Give some thought to putting a door on each end for additional flexibility. Mine has that, and I do use the other door with a garbage bag to blast larger items.
You also need a very good recirculating filter or you won't be able to see a darn thing inside while you're blasting. I'd be very surprised if your shop-vac filter could keep up. You also want to trap out only the dust, and send the reuseable media back to the hopper. I got lucky and found a blast cabinet, recirc fan, and filter cabinet cheap on CL. Took some work to get it going again, but it works REALLY well and I use the heck out of it.
Also note that you're gonna need a LOT of compressed air to run the thing. The compressor here is an ancient two stage SpeedAir with a 7.5 HP motor, the biggest I can run on the 200 Amp single phase 220V service in the garage. It runs almost continuously when I'm using the blaster, and that's with the smallest nozzle available.
Today I was blasting a motorcycle wheel, mostly focusing on the hub and spokes. My box is about 4'Wx3'D with a sloping top that was just barely high enough to let me flip the wheel without taking it outside the box. At that depth, I can't reach the far wall, which means if I can't hook it with a tool or by throwing the nozzle and pulling it back, I have to pull my hands out, open the box, and move the object closer to the glove ports. It's a PITA to have to stop and pull your arms out of the gloves because going back in the sleeves are so long you can't really reach to the end and the gloves are stiff enough that grabbing the sleeve with one hand while you push your hand into the other glove isn't easy.
The window was broken when I got my box, so instead of buying an expensive replacement, I made up a frame from some angle iron and used rubber to make a gasket for a piece of safety glass. Works great, but after 7 years of use, it's become pitted enough that I should order a replacement, available from any glass cutter.
You're also gonna need a light to see what you're doing. Mine sits on top of the viewing port, and shines into the box from the outside. That keeps dust and junk out of the light and greatly simplifies wiring. The light fixture is mounted on a hinge so I easily swing it up for maintenance or to clean the glass port on the outside.
There's also a grate on the inside of the box to support the work being blasted. The one that came with the box was all rusted out, so I tossed it and made a new one with a band iron frame and expanded metal floor. Works great, and I've yet to cut through any of the expanded metal.
If I get a chance tomorrow I'll try to post some pictures of my setup. No sense reinventing the wheel...