Fig. 1143.
Boring Tapers with a Boring Bar or Attachment.—In cases where the degree of taper is very great a live centre may be bolted to a chuck plate, as in [Fig. 1143], by which means any degree of taper may be bored. Instead of a star feed, a gear feed may be provided by fastening one gear, as a, on the dead centre, and another, as b, on the feed-screw. The cutting tool must stand on the side of the sliding-head—that is, farthest from the line of lathe centres.
Fig. 1144.
Small holes may readily be bored taper with a bar set over as in [Fig. 1144], the work being carried by a chuck. The head h carries the cutting tool, having a feather which projects into the spline s to prevent the head from rotating on the bar. To prevent the bar from rotating, it is squared on the end f to receive a wrench. The head is fed by the nut n, which is screwed upon the bar. w, w, w, w are merely washers used to bring the nut n at the end of the thread when the head is near the mouth of the work, their number, therefore, depending upon the depth of the work. A bar of this kind is more rigid than a tool held in the tool post.
Fig. 1145.