As soon as a nut is fixed the outer face should be reduced, a proper amount of metal being left for turning the opposite face. This reduction of the face at the beginning of turning is more or less requisite in proportion to the amount which is to be removed, because if this superfluous part is not at first cut off, it must be both bored and screwed. By shortening the length of the hole previous to boring, it can be bored and screwed with but a comparative short length of the slide-rest tools projecting from the tool-holder, and therefore can be more easily cut, through the tool affording proper resistance to the metal.

For boring an ordinary iron or steel nut an ordinary slide-rest borer may be used, having a vee-point cutting part similar to that shown by Fig. 1054 ; but not a U-point, or round-nose, as it is termed, the small amount of curved part which is requisite being shown in the Figure. In order to allow such a tool a free passage through the nut, the hole must have been previously made large enough, either by having been punched, cast, or drilled, supposing that the hole is small when compared with the thickness of the borer.

It is not requisite to use a solid tool, except for small holes; for holes of three, five, or seven inches in diameter a slotted tool is preferable. An end of such a tool is denoted by Fig. 1051, in which small cutters can be securely held, and from which they can be easily detached to be repaired, or to make room for others. The cutter shown keyed in this Figure is suitable for boring iron or steel, and has a vee-point slightly curved at the extremity, resembling the point in Fig. 1054.