I wanted the left edge of the jaw of the front vise to be flush with the left edge of the top, the right edge with the left edge of the left front leg. So the amount of overhang on the left depends upon the width of the front vise jaw. The width of the jaw is, at a minimum, the width of the plate that supports it, but it's normal to make the jaw extend a bit beyond the plate. How far? The more it extends, the deeper a bite you can take with the edge of the vise, when, for example, you are clamping the side of a board being held vertically. But the more it extends, the less support it has. I decided to extend by 1-12", which gives me a 2-1/2" bite, and which should still provide solid support, given that the jaw is 1-1/2" thick. This means the top needs a left overhang of 12-1/4".
Students in the beginning woodworking class learn how to use a variety of tools, including a band, miter and table saw, a drill press, a jointer and a planer. Through the lathe technology class, students become familiar with a number of cutting, scraping and finishing techniques. Successful completion of the course leads to a lathe certification for the wood shop.
The base needs to be as wide as the sum of width of the guide strip and the distance from the edge of the shoe, plus a bit extra, With my saw, the overhang is 3-1/2", so I made my guide strip 5-1/2" wide. The distance between from the edge of the shoe to the blade is about 4-1/2", so the base needs to be at least 10" wide. Since I was working with a 24" wide sheet, I just sliced it down the middle.