The general principles guiding the forms, the shapes and angles, and the action of the cutting edges of all turning tools, together with illustrations of those most generally in use, are given in Chapter XXIV (Turning-Tools. Section I. - Facility Of Turning Compared With Carpentry). of the second volume of this work; that should be perused, but various points there mentioned will be adverted to, so far as may appear necessary, in this and succeeding chapters. It is not proposed however to enter a second time upon the processes and manipulation, by which the grinding and setting of all the different turning tools are accomplished, these subjects having been treated at length in the third volume, to which the reader is also referred; but it will be convenient to note, that the cutting edges of all the softwood tools are ground to an angle of from 25° to 30°.

The gouge and chisel, shown on the face and in profile figs. 325 to 330, are the tools principally used for external softwood turning, they vary in size, according to that of the work upon which they are employed, and range from about one eighth, to about two inches in width of blade, and are of proportionate thickness. These and the other softwood tools, are handled in great measure according to their size, the smaller in short and the larger in long handles; the complete tools so handled, measuring about 8 to 13 inches and 15 to 24 inches respectively, in total length. The medium and most useful size of the gouge, is from half to threequarters of an inch wide, and that of the chisel, from threequarters to one inch wide; which tools in long handles, measure from 14 to 20 inches in total length.

The turner's gouge is ground on the convex face only, and obliquely to its sides or edges, to give it an elliptically formed cutting edge, and to obliterate the sharp corners that would be formed, were the tool ground square across the end in the manner of the carpenter's gouge. The elliptical cutting edge is necessary, to prevent the corners catching the work, and to permit the gouge to occupy and be moved in less space, in turning small curves and mouldings; for which latter reason, the shape is perhaps carried to a rather greater extent with the smaller sized tools.

Fig. 325. 326. 327. 328. 329. 330. 331. 332. 333. 334.

Section II External Tools Leverage Position Of The 400273

The cutting edge of the chisel, for the sake of greater convenience in holding the tool to the work, stands obliquely, forming angles of about 70° and 110° with the parallel sides of its shaft, fig. 329; and it is ground with a bevil on both faces, fig. 330, to form the cutting edge in the center of its thickness. Occasionally it is ground square across, but the oblique edge is far more general and convenient. A tool of the same section, is sometimes ground square across, but with a single bevil on the one face only, figs. 331. 332, like the carpenter's chisel; it is then called a flat tool and has appropriate uses.

The parting tool for softwood, figs. 333, 334, is generally about one eighth of an inch or less in width at the cutting edge, the widest portion of the blade, which, to obtain clearance in the work, tapers gradually thinner towards the thicker stem; it is comparatively of considerable depth or thickness. The cutting edge is divided into two points by an angular groove upon the face, and is ground with a plain bevil upon the under side.

All the hand turning tools may be considered to contain the principle of the lever; their cutting edges are at their shorter ends, the rest on which they are supported is the fulcrum, and their handles or shafts are the longer ends. The command obtained over the tool, in other words the power by which it is controlled and made to penetrate the work, greatly depends as in all similar levers, upon the relative lengths of the two ends. This, can be varied at will with the turning tool, by the position given to the fulcrum, the movable rest, and that of the hand on the shaft of the tool. So that it follows, that the more closely the rest is placed to the work, and the more nearly the hand approaches the extremity of the handle, the greater will be the power obtained, and the less the exercise of strength required for the direction of the tool.

The long handle is necessary to the larger softwood and other tools; among which many have to considerably overhang the rest by their cutting ends; on the other hand it asserts so great leverage, as to require using with caution. Otherwise the edge of the tool may be easily forced into the work, both deeper and faster than it can possibly cut fairly, when it will tear or destroy the work, or perhaps wrench it out of the chuck. The undue force thus exercised by the tool upon the work, is also disagreeably felt by a corresponding wrench to the wrists and arms of the operator.