Lathes - Cutting Tool Shapes - Wisc-Online
The tool in Figure G is called an under-cutting or grooving tool. It is used to cut grooves as shown in the figure. With the proper clearances, the tool can plunge, or cut to left or to the right. The tool in Figure H is a cut-off or parting tool. This tool is used to cut off stock to finished length while the part is being held in a chuck.