Scrub planes are not exclusively used to mill wood to the required dimensions; they are also ideal for hogging off large amounts of wood in everyday woodworking situations.
In this video, Paul Sellers walks you through the steps to customise a basic No.4 Bailey pattern plane into a versatile and fully functional scrub plane, which will probably become one of your favourite plane additions. One great advantage about using a smoothing plane as a scrub plane is that it's not irreversible; you can simply load it with a regular, un-fettled cutting iron again, and you can continue using the same plane as a smoothing plane.
To find out more about Paul Sellers and the projects he is involved with visit http://paulsellers.com