The jaw for the front vise needed to be 10" long - to span the distance from the leg to the end of the top, 1-1/2" thick - to allow for benchdog holes to be drilled in it, and 5" tall. The end vise was mounted 3/4" lower than the front vise, and the screw and guide rods were thicker, so its jaws needed to be at least 6-1/2" tall. Again, they needed to be 1-1/2" thick to allow for benchdog holes, and 23" long to span the width of the bench.
Clamp the inner jaw of the end vise in position, leaving a little bit to trim off later, and then use the dowel and dowel center trick through the screw and guiide rod holes of the vise base plate to mark the position of the screw and guide rod holes in the jaw. Remove the jaw and drill 1-1/8" holes in the marked positions. I used the drill guide for most of the holes, and drilled freehand for the last bit. When you're starting a spade bit in a deep hole like this, start the drill very slowly, and the bit will move the drill into a perpendicular position. Start it too fast and the bit will bind and you'll damage the sides of the hole.
Put the upper panel of MDF on your glue-up surface, bottom side up. Put the bottom panel of MDF on your other surface, bottom side down. (The panel with the holes drilled in it is the bottom panel, and the side that has the your layout diagram on it is the bottom side.) Chuck up in your drill the appropriate driver bit for the screws your using. Make sure you have a freshly-charged battery, and crank the speed down and the torque way down. You don't want to over-tighten the screws, MDF strips easily.
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.
Beyond the weight capacity, the Grizzly is also the largest table top on our list and in more ways than one. For a workspace, the Grizzly provides 5’ of length by 2 ½’ of width. There is not another table that really comes close to that size. Another size advantage of the Grizzly bench is the table top’s thickness. While the standard thickness of the table top for a quality woodworking bench is 1” with lesser models often offering only ¾” of thickness, the Grizzly provides a 1 ½” thick table top.