Part 18 (2/2)

The cutter for the inner bearings is shown at _c_.

[Ill.u.s.tration: Fig. 13. Facing and Turning f.l.a.n.g.e of Differential Gear Casing]

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 f.l.a.n.g.e _F_ at right angles to the bearings. Circular f.l.a.n.g.es 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 f.l.a.n.g.e, 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 ill.u.s.tration shows the tool set for turning the outside or periphery of the f.l.a.n.g.e. This is done by setting the tool to the proper radius and then feeding the work horizontally by s.h.i.+fting 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 f.l.a.n.g.es of cylinders which are to be bored, and for similar work.

[Ill.u.s.tration: 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.

=Fixture for Cylinder Lining or Bus.h.i.+ng.=--A method of holding a cylinder lining or bus.h.i.+ng 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 s.p.a.ced 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 finis.h.i.+ng cut, so that the work can spring back to its normal shape.

[Ill.u.s.tration: Fig. 15. Cylinder Lining mounted in Fixture for Boring]

[Ill.u.s.tration: Fig. 16. Detrick & Harvey Horizontal Boring Machine of the Floor Type Boring Engine Bed Casting]

=Horizontal Boring Machine of Floor Type.=--The type of horizontal boring, drilling and milling machine, shown in Fig. 16, is intended for boring heavy parts such as the cylinders of large engines or pumps, the bearings of heavy machine beds and similar work. This machine can also be used for drilling and milling, although it is intended primarily for boring, and the other operations are usually secondary. This design is ordinarily referred to as the ”floor type,” because the work-table is low for accommodating large heavy castings. The spindle _S_ which drives the boring-bar, and the spindle feeding mechanism, are carried by a saddle. This saddle is free to move vertically on the face of column _C_ which is mounted on transverse ways extending across the right-hand end of the main bed. This construction permits the spindle to move vertically or laterally (by traversing the column) either for adjusting it to the required position or for milling operations. The spindle also has a longitudinal movement for boring. There is an outer bearing _B_ for supporting the boring-bar, which also has lateral and vertical adjustments, so that it can be aligned with the bar.

The work done on a machine of this type is either clamped directly to the large bed-plate _A_ (which has a number of T-slots for receiving the heads of the clamping bolts) or, in some cases, a special fixture may be used or an auxiliary table. Boring machines of this same general construction are built in many different sizes. The main spindle of the machine ill.u.s.trated is driven by a motor located at the rear of the vertical column _C_, the motion being transmitted to the spindle through shafts and gearing. The casting _D_, shown in this particular ill.u.s.tration, is for a steam engine of the horizontal type, and the operation is that of boring the cylindrical guides or bearings for the crosshead. These bearings have a diameter of 15-3/4 inches and are 37-3/4 inches long. In boring them, two roughing cuts and one finis.h.i.+ng cut are taken. The end of the casting, which in the a.s.sembled engine bears against the cylinder, is then faced by means of a regular facing arm.

After removing the boring-bar the table _E_ of the special fixture on which the casting is mounted is turned one quarter of a revolution. A large milling cutter 24 inches in diameter is next mounted on the spindle of the machine, and one side of the main bearing, as well as the pads for the valve-rod guide-bar brackets, are milled. The table is then revolved and the opposite side of the main bearing is milled in the same way, the table being accurately located in the different positions by an index plunger _F_ which engages holes on the under side. The spindle is now moved upward to allow the table to be turned so as to locate the bearing end of the frame next to the headstock of the machine. The milling cutter is then used to machine the inside and top surfaces of the main bearing. By turning the fixture and not changing the position of the casting after it is bolted into place, the various surfaces are machined in the correct relation to one another without difficulty. This is a good example of the work done on horizontal boring machines of the floor type.

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