Regardless of which type of screw you use, you'll need to flip the panel and use a countersink drill to on all of the exit holes. Drilling MDF leaves bumps, the countersink bit will remove them, and will create a little bit of space for material drawn up by the screw from the second sheet of MDF. You want to remove anything that might keep the two panels from mating up flat. I set a block plane to a very shallow bite and ran it over what was left of the bumps and over the edges. The edges of MDF can be bulged by by sawing or just by handling, and you want to knock that down.
Before you start cutting or drilling the pieces that will make up the top, determine the layout of the top. This should include the dimensions of the MDF, the dimensions of the edging, the locations of the vises, and of the screws or bolts that will support the vises, and of all of the benchdog holes and of all of the drywall screws you will use to laminate the panels,
2 - use a plunge router with a bottom bearing cuter bit such as this from rockler: http://www.rockler.com/product.cfm?page=25160&site=ROCKLER .... I thought to use the short one as I plunge it directly downward in the centre of the hole until the bearing reaches within the tabletop hole. I suppose one could use a long one, but the stubbiness seemed more practical (the big bearing ensured accuracy?)
Out of all the shed books I have read, this book stays by my side while I hammer in the yard. The book is well written by what appears to be a non professional book writer (A Good Thing). It reads as if you are getting advise in laymans terms from your neighbor "The Craftsman", a welcome change from the DIY books, that assume a level of expertese. The level of detail is high and discusses gotcha's, advise, and trade "secrets" that could have only come from years of personal experience building sheds.
Synopsis: No room in the garage? Basement not an option? Consider what Ken St. Onge did when he needed shop space: He bought a prefabricated shed and converted it into his full-time woodshop. Because a pre-built shed doesn’t need a cement foundation and is built in a factory, it’s much less expensive than building an addition or stand-alone shop on your property. It can have taller ceilings than a garage and bigger doors than a basement, both big pluses for a woodworker. You can put a shed just about anywhere, too. Here’s a soup to nuts look at Ken’s experience, so you can gauge whether a shop in a shed is right for you.