The bearers of the five inch foot lathes described, are usually from three to three feet six inches in length, but, as a portion of this space is occupied by the lathe heads, the length of work that can be turned between the centers, does not exceed twenty two to twenty four inches. From necessity in the mode of construction, or in the material of turned works, this length is nearly always more than sufficient; on the other hand, the total range of five inch center lathes may be readily extended by the addition of lengthening bearers, to embrace works to about four feet in length.
The most approved forms of lengthening bearers, fig. 185, are of iron, planed and scraped true and parallel, upon their upper and under surfaces; the latter being solid and fixed to the lathe bearers by a tenon and two bolts, permitting longitudinal adjustment, to place the small popit head at about the required distance from the lathe head. The popit head and the small hand rest are also adjustable, and are fixed when in position, by bolts screwing into nuts, fig. 186, sliding in a true under cut groove; the ordinary hand rest being used for the support of the tool, in turning that portion of the work situated between the chuck and the front end of the lengthening bearers. No greater length than is requisite to accommodate the work, is allowed to overhang the lathe bearers, and with the same view to avoid vibration, a wooden strut extending to the floor, is attached by a screw to the inner side of the rectangular projection at the end.
The majority of the shafts and rods for which the lengthening bearers are necessary, seldom exceeds about two inches in diameter; but their length in comparison with the smallness of their diameter, very generally causes the work to be pliable, and to spring away from the turning tool. With the larger works, the piece having been first roughly rounded, the work is supported against the thrust of the tool by the left hand held around it from above, in the manner described in turning soft wood cylinders. "Works of smaller dimensions, may be stiffened and checked in their vibrations by the sliding guide fig. 139, or some other support, mounted upon the lathe bearers, and placed about the middle of their length; the hand being still held around and travelling along the work with the tool. A second stay or support is sometimes simultaneously
Fig. 188mounted upon the lengthening bearers. With very long works, the turning may be assisted, especially when no sliding guide is available, if the work be occasionally changed end for end between the chuck and the popit head. The tool may then always operate upon the half of the work next to the lathe head, which half acquires somewhat less oscillation; and the small hand rest is then only employed, to support the tool over a short length, joining the two halves, that have both been previously turned from the ordinary hand rest.
A rough method of. lengthening the lathe bearers, figs. 187. 188, is sometimes resorted to, and may often be found convenient enough for an occasional purpose. A center screw is carried by a block of wood attached at the end of a piece of strong plank, the latter at the opposite end, having a second piece of wood fixed beneath forming a tenon, which together with two bolts, holds the whole in position on the bearers. A long screw, sometimes adjustable vertically for height, with two or more nuts, projects from the side of the block to support and fix one end of a long wooden bar, forming the tee; the other end of which is attached to an iron stem, clamping in the ordinary rest bottom. A wooden strut should also extend from beneath the popit head end to the floor, to diminish vibration.