This section is from the book "Lathe Design, Construction And Operation, With Practical Examples Of The Lathe Work", by Oscar E. Perrigo. Also available from Amazon: Lathe Design: Construction And Operation.
The carriage is gibbed to the bed on the outside of the V's, both back and front, thus spreading the gibbed surfaces as far apart as possible.
Following this will come in due order illustrations of a few of the carriages and compound rests built by some of the prominent manufacturers.
Figure 112 shows the carriage, apron front, and compound rest of a New Haven 24-inch swing lathe. The T-slots in the rear wings of the carriage are as shown in Fig. 1ll, but those in the front wing are at right angles. In some cases this is preferable, but if the carriage is to be used much for boring purposes the slots will be found most desirable if all in one direction. The top of the carriage is level, with no obstructions when the compound rest is removed.
The apron front is clear of gears and other similar obstructions, and the uses of the levers are indicated by plain lettering on the front of the apron. As the levers are set in the engravings all feeds are "out." The "star nut" closes the friction of the driving bevel gear, and the feed is "on" to the right or left according as the lever, marked "to reverse all feeds" is thrown to the right or left. To operate either the lateral or cross feeds the upper lever is thrown to the left for "lateral feeds," and to the right for "cross-feed." The lever at the extreme right closes the "split nut" on the lead screw, provided the feeds are not engaged. That is, if the levers are as shown the lead screw nut may be closed. But if the lever "to reverse all feeds" is moved to the right or left, the split nut is locked "open" and cannot be closed.
The feed rod carries two bevel pinions arranged in a sliding frame, operated by the lower lever, the two bevel pinions being adapted to be engaged on either side of the driving bevel gear which transmits the motion through the medium of a conical friction clutch operated by the "star nut" in front of the apron.
Fig. 112. -The New Haven Carriage, Apron, and Compound Rest for Lathes up to 32-inch swing.
Further than these bevel gear connections there are no gears but those leading up to the cross-feed screw and back to the rack pinion and hand-wheel shaft. No worm or worm-gear is used. Consequently the parts are large, strong, and durable.
The compound rest, as will be seen, is of ample proportions, has a graduated base, a convenient removable double crank, and a tool-post provided with a concave ring and washer adjustments for the tool.
The entire mechanism has proven very satisfactory in practical use.
The Hendey-Norton carriage, apron, and compound rest is shown in Fig. 113. It is not as conveniently arranged in front of the apron as in the last example. The carriage has the projecting dovetail in the center instead of the flat surface, and only two T-slots are shown in the front wing of the carriage.
The compound rest is a nice piece of designing and construction. It has a graduated base and a tool-post of unusual strength and rigidity. The single crank on the compound rest screw is not as convenient for many uses as a double crank. The cross-feed screw carries a very convenient graduated disc, which ought to be provided for all lathes up to 32-inch swing, and is useful in many ways for even larger lathes where fine work is to be done.
Figure 114 shows the carriage, apron, and compound rest of the Blaisdell lathes. While the construction is strong and substantial, it cannot be said that it is very symmetrical or with any attempt at fine lines. The arrangement of the apron front is hardly modern, although there is no gearing or unnecessary part exposed.
Fig. 113. - The Hendey-Norton Carriage, Apron, and Compound Rest.
A single T-slot is located in the front carriage wing. The carriage and apron are the same length, which usually indicates that the bearing of the carriage on the bed is not as long as it might be to good advantage. The cross-slide dovetail projects above the general level of the carriage so that it would be in the way for boring operations.
Figure 115 shows the front of the carriage and the compound rest of a 60-inch swing, New Haven lathe. The top of the carriage is level and has three T-slots on each side, in the front wings. The carriage is very massive, weighing about 1,600 pounds, and the compound rest considerably over half that amount.
The compound rest has a large, circular, graduated base and supports a very broad and heavy tool block. The tool is held by heavy steel clamping bars held up under the nuts by large spiral springs so that the tool may be readily introduced. These clamping bars project, at the ends, beyond the holding-down studs so that the tool may be placed outside the studs when the nature of the work requires that position.
Fig. 114.-The Blaisdell Carriage, Apron, and Compound Rest.
Fig. 115. - The New Haven Carriage and Compound Rest for Large Lathes.
The entire device is very strong and rigid and capable of withstanding very heavy cuts. There is a power cross and angular feed in addition to the facilities for hand feeding in all directions.
Further illustrations and comments upon the various features of this class on the lathes built by different makers will be found in later chapters of this work, describing the entire lathes, and to which the reader is referred for further information.
A practical machinist has recently made the following criticisms upon one of the popular lathes which shows the standpoint from which the practical men look at some of the lathe features. It is so eminently commendable as to be well worth preserving.