The internal cylinder when of ivory or rare woods, may be roughed out in solid pieces, in the manner referred to in the first volume for the preparation of ivory; the material being removed and saved for use in the form of rings and cores. Short cylindrical apertures completely through from one face of the work to the other; may have the center or core cut out as a solid with the parting tool, fig. 389, held horizontally and parallel with the axis of the lathe ; cutting from one surface of the work only. When the thickness of the piece approaches two inches, it is more convenient and less wasteful to chuck the work twice, making an incision of only half the depth from each face. The parting tools employed vary with the size of the work, from about a thirty second, to an eighth of an inch in width, and from about a quarter to half an inch in depth; they are used with and without the armrest, the smaller in short and the larger in long handles.

The parting tool soon binds and then becomes fast in the narrow circular groove made by a single cut, to which the flat side of the tool lies as a chord. Immediately it commences to bind therefore, the tool is withdrawn, and re-applied to cut a second groove by the side of and merging into the first, fig. 424. The widening of the groove allows the tool to act freely, and the two cuts are alternately prolonged until the work is pierced completely through. A groove less than twice the width of the tool, usually suffices for works that are comparatively large in diameter and of no great thickness; but greater width is required in small cylinders, from the increased curvature of the circle compared with the straight line of the side of the tool. In deep grooves, even when they are of large diameter, the separate cuts are not very easily kept distinct; the sides of the curve having a tendency to become taper. Such grooves are widened, by additional cuts near the surface, while at the bottom, their width is hardly greater than that of the edge of the tool itself, the form conveniently admitting the increasing thickness of the shaft of the parting tool, with which it nearly agrees in section.

Cylinders closed at one end, have the material removed as a series of rings, one from within the other. The inside parting tools, fig. 391, are employed to cut a surface groove in the body of the work, fig. 423; the diameter to which this surface groove extends, is then noted and marked on the face of the work, and a cylindrical groove, cut down from the face in the manner last described, meets it and separates the ring. An aperture is previously turned or bored in the work to the depth of the required cylinder, and equal in diameter to the width of the inside parting tool, measured from the cutting edge to the back of the stem. A tool having a short blade, requiring a hole of small diameter, is first used to remove a thin ring; the increasing diameter of the aperture, then admitting tools with longer blades, removing thicker rings.

The narrow and comparatively long blade of the inside parting tool, fig. 391, has much greater depth than width, and stands at right angles to its shaft, which is held parallel with the mandrel axis. Should the shaft be inclined horizontally, the long blade binds against the sides of the groove in the direction of its length, but if vertically, then by its sides or depth ; the slender blade gives but little warning, and may be readily broken off if the tool be used with too great force, or if it bind sensibly in either direction. The accident should not happen if the shaft be held fairly parallel.

The tool in either a short or long handle is held upon the armrest after the horizontal manner, its shaft pressed against the hook by the left thumb; but, as the cutting edge is at a distance from its point of support according to the depth of the cylinder, the right hand is correspondingly shifted back down the handle of the tool. The shaft is supported on the armrest at a point about one third from the cutting end, between that, and the right hand upon the handle, this gives increased power for the guidance of the tool, and allows any divergence of the shaft from parallelism with the mandrel axis to be readily seen and prevented. A slight upward twist is also constantly maintained upon the handle of the tool, to keep the blade in its correct cutting position; the resistance of the cut having a tendency to force it to fall below the radial line ; and the cutting pressure is principally given by the weight of the body, gently poised backwards. When the depth of the cylinder is too great for the armrest to give sufficient control, a long handled tool is employed upon the tee, placed at right angles; the tool being held in a similar manner to the right side tool in roughing out deep internal work.

The blade of the inside parting tool tapers from the cutting edge in both directions, giving sufficient clearance for thin rings to be separated by a single cut; but this taper is insufficient for thick rings, when to avoid friction, the groove requires to be about one and a half times the width of the blade. The tool is then allowed to cut the first groove to a moderate depth, withdrawn entirely clear of it, and re-applied, shifted up the cylinder about half its own width; here, a second cut is made, merging into and nearly to the same depth as the first, but leaving a step. The tool is then returned to the first groove to increase its depth, and then again transferred to the step for the second, the two cuts being continued alternately until the widened surface groove is of the required depth. The increased width given to the groove, materially assists the escape of the shavings, but these especially in ivory, nevertheless frequently collect and form a small hard obstruction at some spot at the bottom of the groove. The accumulation, which is immediately felt by the blow it gives to the edge of the tool at every revolution, cannot be removed by force; and if it be neglected rapidly increases, frequently forming a sufficient obstacle to break off the blade of the tool. The shavings will also sometimes collect in a similar manner, at the bottom of the groove cut from the surface by the ordinary parting tool. Directly the blows are recognized, either tool is withdrawn from the bottom of its groove, and only sufficiently re-advanced to attack the top of the obstruction; this is then easily reduced and removed by the intermittent action, when the tool arrives again at its former depth and once more cuts all around the groove.