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 general arrangement and construction of the head-stock, and the gearing contained in the front end of the bed, is well shown in the longitudinal section in Fig. 237, and the end elevation in Fig. 238. In these engravings the location of the "cone of gears" is seen to be in the bed of the lathe instead of in a box or extension in front of it, or partially in the head as is the case of some of the rapid change gear devices. In Fig. 238 the location of the various handles and levers for controlling the change gear device is clearly shown and their use and operation may be readily seen and understood. The movable or sliding connecting or intermediate pinion, carried by a lever which is held in place by a spring pin entering any one of the line of holes shown in the front of the head-stock in Fig. 236, is practically the same as used in the Hendey-Norton lathe and in others of this type. These changes are very quickly and certainly made, and the mechanism appears to be substantial and durable.
Fig. 236. - 20-inch Swing Engine Lathe built by the Lodge & Shipley-Machine Tool Company.
The bed is designed with ample depth and width, and is strongly braced internally by cross girts The surfaces to which the lead-screw bearings are fastened are planed to receive them and the parts are tongued and grooved to insure perfect alignment. The V's are rounded on top to prevent bruising. In lathes of 22-inch swing and larger the beds are additionally strengthened by a central longitudinal brace, in the top of which is a rack into which a pawl pivoted to the bottom of the tail-stock engages, thus affording a positive brace for holding the latter in position against heavy strains. The rear end of the bed is cut down low enough to permit the ready withdrawal of the tail-stock, which is very convenient when turret slides or similar attachments are to replace the regular tail-stock.
Fig. 238. - End Elevation of the Lodge & Shipley 20-inch Lathe.
Fig. 237. - Longitudinal Section of the Lodge & Shiply Head-Stock for 20-inch Lathe.
The carriage is strong and heavy with liberal length of bearing upon the V's the entire length of the carriage, which is gibbed to the bed its entire length also. In place of an inside V at the front of the bed, the surface is flat for the carriage to find an additional bearing, thus shortening the distance between the supports of the carriage and so affording additional strength and rigidity immediately under that portion supporting the compound rest in its usual position. The V's are kept clean and also lubricated by a specially designed wiper and oiler fastened to the ends of the carriage. This not only insures the proper lubrication but prevents grit and dirt getting between the carriage and the V's, and so destroying their accurate bearing and smooth surface contact.
The apron is of ample strength and made specially rigid by three braces through its entire length and a longitudinal brace across the bottom. It is tongued and grooved into the carriage, and firmly bolted to it. No worm or worm-gears are used, a compact arrangement of a large bevel gear and two bevel pinions mounted in a sliding frame taking the place of the older method of construction. There are few gears used in this construction, and all of them are of steel and run on hardened and ground steel studs or shafts. The lead screw passes through the double bevel pinions, and is splined to them by a spline reaching the entire length of the gear sleeve, the edges of the spline being carefully rounded to prevent the possibility of injuring the split nuts, which are made from solid metal and then split, instead of being lined with babbitt metal as usual. These nuts are held in planed grooves in the back of the apron, no clamps or screws being used. This holds them very rigidly under the heaviest strains. In the larger lathes it is, of course, necessary to back gear the operative parts for ease of handling. This is done with few gears, which are made heavy and strong. The lead screw threads are never in use except when thread cutting, the locking out of the thread cutting or the regular feed device being automatically and surely provided for by a simple device. The rear of this apron is shown in Fig. 239, by which its compact form and mechanical design is clearly shown. This establishment builds other types of lathes of very practical and useful forms and equally good design, as well as various attachments and accessories which will be found illustrated and described further on in this book under their appropriate headings, and to which the reader is referred for information of this character.
Fig. 239. - Apron of the Lodge & Shipley 20-inch Lathe.