After the bearings are bored, the circular table is turned 90 degrees and the work is moved closer to the spindle (as shown in [Fig. 13]) for facing flange F at right angles to the bearings. Circular flanges of this kind are faced in a horizontal boring machine by a special facing-arm or head H. For this particular job this head is clamped directly to the spindle sleeve, but it can also be clamped to the spindle if necessary. The turning tool is held in a slotted toolpost, and it is fed radially for turning the side or face of the flange, by the well-known star feed at S. When this feed is in operation the bent finger E is turned downward so that it strikes one of the star wheel arms for each revolution; this turns the wheel slightly, and the movement is transmitted to the tool-block by a feed-screw. The illustration shows the tool set for turning the outside or periphery of the flange. This is done by setting the tool to the proper radius and then feeding the work horizontally by shifting the work-table along the bed. By referring to [Fig. 12] it will be seen that the facing head does not need to be removed for boring, as it is attached to the spindle driving quill and does not interfere with the longitudinal adjustment of the spindle. This facing head is also used frequently for truing the flanges of cylinders which are to be bored, and for similar work.
Fig. 14. Example of Work requiring Boring and Milling
[Fig. 14] shows another example of work which requires boring and milling. This casting is mounted on a fixture which is bolted to the main table. In this case the circular table is not necessary, because the work can be finished without swiveling it around. After the boring is completed the edge E is trued by the large-face milling cutter M bolted to the spindle sleeve. The irregular outline of the edge is followed by moving the table crosswise and the spindle vertically, as required.
Fig. 15. Cylinder Lining mounted in Fixture for Boring
Fixture for Cylinder Lining or Bushing.—A method of holding a cylinder lining or bushing while it is being bored is shown in [Fig. 15]. The lining L is mounted in two cast-iron ring-shaped fixtures F. These fixtures are circular in shape and have flat bases which are bolted to the table of the machine. On the inside of each fixture, there are four equally spaced wedges W which fit into grooves as shown in the end view. These wedges are drawn in against the work by bolts, and they prevent the lining from rotating when a cut is being taken. This form of fixture is especially adapted for holding thin bronze linings, such as are used in pump cylinders, because only a light pressure against the wedges is required, and thin work can be held without distorting it. If a very thin lining is being bored, it is well to loosen the wedges slightly before taking the finishing cut, so that the work can spring back to its normal shape.