Fig. 737.
When work of considerable weight requires to be bored with holes of moderate diameter, it is more convenient that it remain fixed upon a table, and that the boring tools rotate, and a machine constructed by the Ames Manufacturing Company for this purpose is shown in [Fig. 737]; a standard occupies the position of the ordinary tailstock. It carries an horizontal table, or angle plate, on which the work may be chucked. This table is capable of a vertical and a cross shear movement, so that when the work is chucked upon it, holes whose axes are parallel, but situated in different locations upon the same surface, may be drilled or bored by so moving the table as to bring each successive hole into line with the live spindle. The feed motions are as follows:—
At the back of the smallest step on the cone and fast on the cone spindle is a gear-wheel gearing into a pinion, which drives the lower shaft shown behind the back bearing, and on this shaft are two pinions. One drives the upper feed cone, shown at the back of the back bearing, which cone connects by belt to the feed cone below, which operates a traverse feed for the work table; the other drives the tool holding spindle which passes through the cone spindle. This tool holding or driving spindle is threaded at its back end, passing through a nut which causes it to self-feed from left to right, or in other words, towards the work table. To throw this feed out of operation the pinion on the end of the lower or feed driving spindle is moved laterally out of gear with the pinion driving it.
To provide a quick hand-feed traverse the shaft or spindle, shown with a hand-wheel, is provided, being connected to the tool driving spindle by gearing.
When employed to operate a boring bar, a bearing to support the bar at the tail or footstock end may be bolted to the table, such bearing carrying a bushing which may be changed to suit the diameter of the boring bar.
Fig. 738.
[Fig. 738] represents a cylinder boring lathe. d is the driving cone, on whose shaft is the worm w, driving the worm-wheel g, which is fast upon the boring bar g, having journal bearing in the standards h and h′, the latter of which must be moved out of the way to get the work over the bar. h is a head provided with slots to carry the cutting tools; h is a close sliding fit to the bar g, and is traversed along g as follows:—g is hollow and there passes through it a feed screw, which operates a nut on h, which nut passes through a longitudinal opening in the bar g. At the end of this feed screw is the gear-wheel d. Now fast upon the end of g, and therefore rotating with it, is the gear a, driving gear b, which is fast on the same sleeve as c, which it therefore drives; c drives d. The diameter of a is less than that of b, while that of c is less than that of d; hence the rotation of d is slower than that of a, and the difference in the relative velocities of d and a causes the feed screw to rotate upon its axis and feed the head h along the bar. If c be placed out of gear with d, the feed screw (and hence the head h) may be operated by the handle e.