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1911 Article-Pollock and MacNab, Ltd.-18 in. Swing Apollo Capstan Lathe |
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Machine Tools Commonly Employed In Modern Engineering Workshop, V1, 1911, pgs. 74-76 |
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8/6/2020 10:06:10 PM |
The Apollo Capstan Lathe of 18-in. swing over the bed, manufactured by Messrs. Pollock & Macnab, Limited, Manchester, is illustrated in fig. 98, upon which the principal parts are clearly indicated by name.
In the first machine the turret is mounted upon a slide, and the machine is therefore of the Capstan type, whereas in the second example the turret is mounted directly upon the saddle.
From the illustration, fig. 98, it will be seen that the capstan machine is mounted within a large oil tray, supported at the one end upon a cabinet and at the other by a double foot. The bed itself is of box section, strongly ribbed to ensure the required rigidity and strength. Flat- machined surfaces with square lips are provided on the upper side for the support and guidance of the headstock and the front and capstan carriages.
The headstock is of the single-pulley all-gear type, the advantages of which have been already referred to. It provides a series of sixteen speeds in geometrical progression ranging from 19.7 to 390 revolutions per minute when driven by one belt direct from the line shaft, and the various speed changes can be readily made by suitably manipulating the speed variator levers, which control the friction clutches and sliding gears within the head. There is also provided a stopping and starting lever by means of which the motion of the machine can be stopped without shifting the main driving belt. As the machine is designed for both chucking and bar work the spindle is bored throughout 2 5/8 in. diameter, and on the nose there is provided a flange, to which the chuck is bolted directly; an arrangement which reduces to a minimum the overhang of the chuck beyond the front bearing.
On the front of the bed beneath the headstock is mounted the feed and screw- cutting box, which is self-contained, and which can be removed for inspection or repair without disturbing other portions of the machine. For every spindle speed in the forward and reverse directions it provides four rates of feed, and also four different threads for screw-cutting, without necessitating: the alteration of change wheels. The four changes referred to can be obtained by the movement of the feed-variator lever into one or other of its four positions; but there is provided, in addition, on the head- stock a change-feed lever, by means of which the four rates of feed can be doubled.
Upon the front carriage is mounted a cross slide carrying at the front a four-tool revolving rest, and at the back a single tool -post. The square rest is located by ground steel thimbles and is securely clamped when set by means of the central hand lever. Eight automatic cross and longitudinal traverses are provided, and the motions are derived from the slide shaft through a dropping worm, by means of which the motion can be instantly stopped or started when desired. As the apron is of the double-frame type all the shafts are supported upon two bearings and none is over hung. For screw -cutting operations a clasp nut is closed upon the chaser shaft by operating a handle indicated on the front of the apron; and by suitably setting the feed- box change levers four different threads can be cut with one copier. Both the longitudinal and the cross motions are controlled by adjustable dead stops and trip mechanisms. The longitudinal motion is controlled from a bar at the front of the machine provided with four slots and four adjustable tappets, one for each tool. In a similar manner the cross traverse is controlled by a bar placed across the carriage. An interlocking device prevents the simultaneous engagement of the screw cutting and the feed mechanisms.
The capstan is hexagonal and is revolved from one tool position to the next in the usual way by moving back the capstan slide by means of the star handle. When desired, however, it can be wound round by hand through the whole circle. Each face is bored to receive bars, drills, and other tools, and the holes are carried through the turret so as to enable the work to pass right through, thus simplifying the tool holders and reducing the overhang. The capstan slide is exceptionally long and rigid, and the working parts, such as the revolving, dividing, and locking mechanism, are of hardened steel, ground and fitted. A clamping handle is provided for securing the turret, and the slide can also be clamped by means of a small handle at the front guide. The sole piece is lipped and clamped to the shears of the bed, and it can be secured to the latter at any point. The automatic-feed arrangements are similar to those already described in the case of the front carriage. There are six dead stops with trip motions, one for each of the turret faces. When the turret is indexed from one face to the next the hexagonal bar carrying the stops is rotated in such a way that the appropriate stop occupies a vertical position in line with the turret travel stop, which disengages the dropping worm. The worm mechanisms of both the capstan and the front carriage aprons run in oil baths and are provided with ball thrusts.
In the machine illustrated the swing over the bed is 18 in., and over the front carriage in. From the flange of the spindle to the turret face the maximum distance is 3 ft. 5 3/4 in. and the length of the bed is 7 ft. 9 in. The turret has an automatic travel of 18 in. |
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1911 Pollock and MacNab, Ltd.-18 in. Swing Apollo Capstan Lathe
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