As shown in the cut the handle d of d is at its lowest point, and the half-nuts n′ and n are in gear upon the feed screw; but suppose d be raised, then the grooves a a would force their respective pins n up the slots c, and these pins n being each fast to a half of the nut, the two half-nuts would be opened clear of the feed screw, and the carriage would cease to be fed.

The hand-feed or guide-carriage traverse motion is accomplished as follows:—b provides at e journal bearing to a stud on which is the hand wheel shown in the general cut; attached to this hand wheel is a pinion operating a large gear (also seen in general cut) whose pitch line is seen at g, in figure. The stud carrying g has journal bearing at f, and carries a pinion whose pitch circle is at h and which gears with the rack.

VOL. I.EXAMPLES IN LATHE CONSTRUCTION.PLATE V.
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Fig. 527.
Fig. 528.
Fig. 529.

[Fig. 527], which is taken from The American Machinist, represents an English self-acting lathe capable of swinging work of 12 inches diameter over the top of the lathe shears, which are provided with a removable piece beneath the live centre, which when removed leaves a gap, increasing the capacity of the lathe swing. The gears for reversing the direction of feed screw motion are here placed at the end of the live head or headstock, the screw being used for feeding as well as for screw cutting.

[Fig. 528] represents a pattern-maker’s lathe, by the Putnam Tool Co., of Fitchburg, Massachusetts. This lathe is provided with convenient means of feeding the tool to its cut by mechanism instead of by hand, as is usually done by pattern-makers, and this improvement saves considerable time, because the necessity of frequently testing the straightness of the work is avoided.

It is provided with an iron extension shears, the upper shears sliding in V-ways provided in the lower one. The hand-wheel is connected with a shaft and pinion, which works in a rack, and is used for the purpose of changing the position of the upper bed, which is secured in its adjusted position by means of the tie bolts and nuts, as shown on the front of the lower shears. This enables the gap in the lower shears to be left open to receive work of large diameter, and has the advantage that the gap need be opened no more than is necessary to receive the required length of work. The slide-rest is operated by a worm set at an angle, so as to operate with a rolling rather than a sliding motion of the teeth, and the handle for operating the worm-shaft is balanced. The carriage is gibbed to the bed. The largest and smallest steps of the cone pulley are of iron, the intermediate steps being of wood, and a brake is provided to enable the lathe to be stopped quickly. This is an excellent improvement, because much time is often lost in stopping the lathe while running at a high velocity, or when work of large diameter is being turned. The lathe will swing work of 50 inches within the gap, and the upper shears will move sufficiently to take in 4 additional feet between the centres.

Fig. 530.

In the general view of the lathe, [Fig. 528], the slide-rest is shown provided with a T-rest for hand tools, but as this sets in a clip or split bore, it may readily be removed and replaced by a screw tool, poppet for holding a gauge, or other necessary tool. To enable the facing of work when the gap is used, the extra attachment shown in [Figs. 529] and [530] is employed. It consists of an arm or bar a, bolted to the upper shears s by a bolt b, and clamp c, in the usual manner, and is provided with the usual slideway and feed-screw f for operating the lower slide t, which carries a hollow stem d; over d fits a hub k, upon the upper slide e, which hub is split and has a bolt at f, by means of which the upper slide may be clamped to its adjusted angle or position. The upper slider h receives the tool-post, which is parallel and fits in a split hub, so that when relieved it may be rapidly raised or lowered to adjust the height of the tool.