Drill four 5/8-in.-dia. 1/2-in.-deep holes on the large disc?inside the traced circle?then use 5/8-in. dowel centers to transfer the hole locations to the underside of the small disc. Drill four 1/2-in.-deep holes on the underside of the small disc and a 1/2-in.-deep hole in the center of the top for the dowel handle. Glue in the dowels to join the discs, and glue in the handle. We drilled a wood ball for a handle knob, but a screw-on ceramic knob also provides a comfortable, attractive grip.
The hacksaw will often damage the last thread when it cuts. Running a nut off the end will fix this. You'll have to run the nut all the way down from the other end. This doesn't take long, if you chuck up the rod in your drill and let it do the work. Hold the rod vertically, with the drill pointing down, and just hold on to the nut enough to keep it from spinning.
The bench I will be describing differs from both of these in a couple of areas, the most significant of which is the top. Allen's top was made from three layers of 3/4" medium density fiberboard (MDF), topped and edged with 1/4" hardboard. Christiana's top was just two layers of 3/4" MDF. My top is two layers of 3/4" MDF edged with 1/2" oak and topped by a 1-1/2" thick edge-glued oak Ikea countertop. My top is more expensive in both time and money than either Christiana's or Allen's. If you're looking to build something fast and cheap, I'd recommend Allen's approach over Christiana's. The hardboard significantly increases the durability of the top.
We cut the supports 16 in. long, but you can place the second shelf at whatever height you like. Screw the end supports to the walls at each end. Use drywall anchors if you can’t hit a stud. Then mark the position of the middle supports onto the top and bottom shelves with a square and drill 5/32-in. clearance holes through the shelves. Drive 1-5/8-in. screws through the shelf into the supports. You can apply this same concept to garage storage. See how to build double-decker garage storage shelves here.
I marked out the one hole location, drilled a shallow 1/16" hole into the top. I then put a 1/16" bit through the hole in my template and into the hole I had just drilled. I lined up the template, and drilled a second hole, then put another bit through that. From then on, I worked entirely from the template. With two bits through the holes pinning the template in place, the other holes in the template would be precisely located (or so the theory goes) on a 4x4" grid.
Of course, few benches can be ideal, and this one does have some drawbacks. That being said, most of the disadvantages of this bench are minor annoyances rather than deal breakers. For instance, this bench does not include any kind of storage whatsoever. Though, it does have the option of adding numerous additional features like a storage area. Still, for the bench, you would expect a drawer at the very least, maybe a shelf below the main table area.