There are two general types of this machine, both of which were designed primarily for boring hollow cylinders too large for boring on the lathe. The two types of the boring machine, each of which has several varieties, are (1) the horizontal boring and drilling machine, and (2) the vertical boring and turning mill. These machines have been developed, as their names indicate, to do other work besides boring.

The boring of large gun tubes, small gun barrels, and long shafts, which may be forged either hollow or solid, is done on a special type of lathe, and cannot be done on the boring machines here mentioned.