A sturdy workbench is a necessity for any metalworking or woodworking shop. Unlike fine furniture, workbenches are not built to be pretty or delicate, and therefore are significantly easier and faster to build than an armoire or a rocking chair. Use hardwood, such as ash or maple, for a super-strong bench, or simple pine framing lumber for ease and economy. Whatever material you use, remember that your bench will undergo significant abuse and must be built strongly enough to withstand it.
Joint and plane all of the two-by-fours so they are straight. Cut to 73 inches as many of them as are necessary to make a panel 24 inches wide when aligned broad side to broad side. Depending on how much you plane off to make them straight, you will require 16 to 20 two-by-fours for the panel.
Glue the two-by-fours together, face to face, so the widest dimension (approximately 3 1/2 inches) becomes the thickness of the panel. Spread glue liberally on the faces so that when you clamp them together the glue squeezes out of the joints. Allow this to dry for several hours.
Cut eight planed two-by-fours to a length of 33 inches. Glue and clamp these together in four pairs, again face to face, to make legs. When they are dry, joint them square, plane them to exactly 3 inches by 3 inches, and cut them to a length of 32 inches.
Make a lower shelf for the bench by gluing together a panel that measures 1 inch by 12 inches by 62 inches. The lower shelf doesn't need to be as strong as the top, so you can glue the two-by-fours edge to edge, making a panel that is roughly 1 to 1 1/2 inches thick.
Make four skirtboards 1 inch by 3 inches by 62 inches and two skirtboards 1 inch by 3 inches by 20 inches. The skirtboards form what is sometimes called the apron, which connects the legs and helps support the top. A lower skirtboard supports the lower shelf.
Drill holes every 12 inches through the wide dimension of the skirtboards. These are for the 4-inch screws that will hold the top to the base.
Lay two of the legs on a flat surface, 62 inches apart. Lay a 62-inch-long skirtboard across their tops. Holding or clamping the skirtboard to one of the legs, drill a hole through the skirtboard and the leg, centred on the leg and 3/4 inch down from the top edge of the skirtboard, of a dimension to allow one 5-inch pan-head bolt to slide snugly through it. Drill another hole below that one, 3/4 inch up from the bottom edge of the skirtboard.
Put bolts through these holes, put washers and nuts on the bolts, and tighten them securely.
Perform the same operation for the other leg, then do the same for the other two legs and another skirtboard.
The skirtboards you have just attached are on the outside faces of the legs. Attach the lower skirtboards to the inside faces of the legs, 4 inches up from the bottom, by drilling through the leg, then the skirtboard. Put the bolts through the legs and into the skirtboards, this will prevent the bolt ends from sticking out when the bench is assembled.
Stand the two assemblies up so they are parallel and 20 inches apart. Bolt a 20-inch skirtboard onto the ends so that it connects the two assemblies and overlaps the ends of the two 62-inch skirtboard. Do the same to the other end.
Fit the shelf in between the legs so it is sitting on top of the lower skirtboards. Secure the shelf to the lower skirtboards with 1 1/2-inch wood screws down through the shelf and into the lower skirtboards.
Place the top upside down on a flat surface. Put the base assembly upside down on the top and centre it. There should be a 2-inch overhang on each side and a 4-inch overhang on each end. Put the 4-inch screws through the holes in the skirtboards and into the top.