Interesting discusion, while most surface grinding is done as a finishing process, as in grinding to achieve a dimension that you cannot get with a milling machine, I often will square my stock on the mill leaving a small amount for grinding. I like to start with a square piece of material. After milling I will surface grind 2 parallel surfaces to size then clamp the stock to a precision angle plate to get the third surface perpendicular to the first 2. One of the first surfaces needs to be clamped to the angle plate at this step. Next place the part on the surface grind table with the 3rd surface down against the chuck. Now I grind the 4th surface, which is parallel the the 3rd to size. Now I have 4 sides of a cube to size and they are parallel and perpendicular to each other. There are 2 more sides to be finished at this time. I place the angle plate on the magnetic chuck and place the part next to the angle plate and turn the magnet on. Now I clamp the part to the angle plate with a clamp or two. The surfaces against the chuck and the angle plate should be one of the finished sides. Turn the magnet off and remove the angle plate and part assembly from the chuck. The surface of the part and the angle plate should be flush at this point. Rotate the angle plate 90 degrees and turn the magnetic chuck on. By doing this, when I grind the 5th surface it should be square to the surface I used as a reference when clamping. The 6th surface can be ground to size now by placing the part on the chuck and turning the magnet on and then grinding to size. Now I should have all 6 sufaces parallel and perpendicular to each other. I know, it seems like a lot of work just to square up a piece of stock but I have found that starting with a piece of stock that is squared up this way leads to a much better finished product. As a caveat, the stock will only be as square as your angle plate and your clamping abilities. When performing the next operations on the mill or lathe, I can indicate any surface and know that my part is in the vise or chuck true. Apprentices in our shop would make our own angle plates and grind them from a journeymans angle plate of known accuracy. The angle plate was then checked in our metrology dept. with a cylindrical square. Our goal was less than .0001 in 6 inches accuacy. The surface grinder is a very useful tool and can make a job much more accurate. I would be lost without mine. Dave