Because of the moving parts involved in expansive bits, they are manufactured in separate sections. All of these sections are drop forged, and their cutting edges are ground sharp.
Up until around 1939, the screw tips on the bits were milled from solid metal. Now, the thread is ground into the guide screws on a ridged grinding wheel.
Once all of the parts have cooled, they can be assembled, ready for shipping. Many expansive bits come with two different sizes of adjustable cutter: one large and one small.
