(1) An attachment on a boring machine to which one or several cutters may be fastened. The cutters are mounted to correspond with the required dimension of the hole to be worked using micrometer screws, or they may use radial feed.
Boring heads may be fastened by a shaft to the spindle of the machine or attached to the boring bar. The body of the boring head, which is kept from turning by a key, is fastened onto the boring bar with a nut; the toolholder is shifted along guides in the body. Radial feed is carried out by means of a screw that turns with each turn of the spindle. The screw is connected to a bevel-gear drive by means of a sprocket, whose teeth strike a stop as the screw turns.
(2) A portable component consisting of multiple spindles on a heavy-duty boring machine. It allows several holes with parallel axes to be worked simultaneously.
(3) A spindle unit on a diamond boring machine.