Middle-axles, paddle-axles, and other large axles, are rotated on the lathe-pivots by means of grippers or carriers consisting of plates and bolts. The lightest of these consist of semicircular bands. Two of these together constitute one carrier, and they are caused to tightly grip the piece in the lathe with screw bolts and nuts. A carrier of this sort need not be very thick, and therefore does not occupy much room; but the two bands together must constitute a sort of ring whose curve is about the same as that of the object to be rotated, to avoid placing packing-pieces between the carrier and the object. A carrier which is suitable for a number of objects of different diameters is one composed of grips having vee-gaps. This also is formed of two thick plates, which are bent to produce the vee-gaps, and punched while on the anvil to produce holes for the screw-bolts. The entire carrier, when complete, somewhat resembles the upper part of the author's slottil, represented by Fig. 558.

The first turning of a shaft consists in roughly removing the greater part of all the superfluous metal from the entire surface, thus making it rotate truly along its entire length previous to finishing any one portion. To do this it is necessary to reverse the article end for end after having reduced about half of its length, and then reduce the other portion. It will be found, when the shaft is removed, that the part which is turned may not rotate truly, by reason of some difference between the conical surfaces in contact, and their wear during the heavy cutting which has been performed, or through the shaft-ends not being right-angular. By reversing the shaft during the roughing, both recesses will become equally worn, and, therefore, not so liable to wear during the finishing of some part, and cause it to rotate untruly.

The tools with which the greater part of the metal is pared off are vee-point tools, having cutting edges slightly curved at the points. Such a tool is caused to cut with both its cutting edges in succession, if the lathe has a traverse gear that can be easily caused to move the slide-rest both ways, in which case both cutting edges of the tool are of the same length. But if the lathe is without such a convenience, single-edged tools are employed. Such a tool will require to be oftener sharpened than one with two edges.

To make the tool cut easily, and to prevent it becoming too soft with the continued friction, it is lubricated with thick soapy water. This is contained in a reservoir which is suspended from a bracket or davit attached to the lathe-carriage, the liquid flowing out upon the shaft from a pipe having a small stop-cock to furnish and arrest the supply as required.

For the purpose of causing a tool to cut with both its edges in succession, two traverse-bands should be provided. These can be applied to any lathe having a proper traverse-gear, similar to that shown in Fig. 1125, and consist of a long band and a short one. Both these are kept ready for use, the long one being crossed, as in the Fig. (1125) when in use, and the short one being used without crossing it. By thus employing two bands, the trouble of buckling in a long band, if only one is used, is avoided.

As soon as a shaft is reduced along its entire length, to very near its finished diameters, and all its shoulders also partly formed, it is said to be truly rough-turned; and to do this properly, so as to leave only a proper quantity for finishing, requires considerable skill. For this purpose, the turner must accurately mark the places for the shoulders as soon as the shaft is made circular, by means of a gauge denoting the various lengths, which is held upon the work for a correct scribing. The making of length-gauges will be mentioned presently; it is sufficient to state here, that after the shaft has been marked, to show the exact places for the shoulders, the metal must be pared off very near to each mark, so as to leave only about a thirtieth or twentieth of an inch to be removed with finishing tools. For producing the shoulders of a straight shaft, it is a good plan to first enter in a short strong grooving-tool having a cutting edge about a quarter or five-sixteenths wide. This is caused to make a series of grooves along the shaft, one at each intended shoulder, an adjusted outside calliper being used at the time, to prevent the tool being entered too far into the metal. Such a tool must be used with oil, or thick soap solution, to make it cut easily; and its cutting edge should be curved outwards and not straight. A tool of this character is shown by Fig. 438, with a slight difference, consisting in the concave recess, or gap at the point, not being quite so deep. Tools of this shape are termed U-point groovers. "When all the grooves are formed along the shaft, the superfluous ridges of metal adjoining the grooves can be easily removed with ordinary vee-roughing-tools having narrow cutting ends ; consequently, much of the reduction with right and left corner tools is avoided.

It is now presumed that the shaft has been accurately rough-turned, so as to cause its entire length to rotate truly, and leave about the same quantity to be cut off any part, in order to attain the finished diameters and lengths. The finishing process can therefore now commence, and the operator should begin by smoothly finishing all the shoulders, or nearly all of them, while the shaft remains in one position in the lathe, without reversing it end for end, if the shaft is of sufficient length to allow room for the lathe-carriage to be moved to the required places. But if it is too short, three or four shoulders at one end of the shaft are to be finished, and also the cylindrical parts of the neck or necks, together with the outer end, previous to reversing the shaft, to complete the other portions. A straight middle-shaft has, in general, two bearing-necks> for the plummer-blocks or entablatures, and two necks for the cams; there are also the two stems or ends for the cranks; consequently, ten shoulders are to be made.

All the shoulders can be smoothly turned, and the curved junctions of the necks also smoothly turned, with the same corner tools which were used for the rough turning, these tools being properly sharpened after the heavy cutting, and the points curved for the smoothing. With these tools it is also necessary to turn a short portion of the cylindrical parts adjoining each curved corner, in order that the sheet gauges for these corners may be applied, and proper curves obtained. The corners, and short portions of the cylindrical parts of a neck, can be finished with right and left corner-tools, excepting a minute amount which is afterwards taken off with polishing tools.

The final smoothing of a bearing-neck is executed with springy tools having convex edges of proper curves to suit the corners or junctions. These corners are finished previous to the middle or parallel part, a calliper being carefully adjusted to make the neck of proper diameter, and carefully used to make both corners of the same diameter. After this, it is easy to reduce the middle or parallel part to the diameter of the two finished ends, with but little or no measurement. The curved corners of a neck belonging to a straight middle-shaft are not very large, the curves resembling those seen in Fig. 1122; neither are the adjoining shoulders very deep; consequently, in many cases, the same convex springy tool which finished the two corners, will also finish the cylindrical part between, and also the two shoulders at right-angles to it. If the mid-part has been smoothly turned to a proper diameter, as it should have been, either with a corner tool, or with a front vee-tool, only a small amount now remains for finishing, which is easily taken off with a springy tool.

It must be noticed that soap solution should be used during the smoothing with both sorts of tools - both the pointed front-tools, and corner-tools, and also the springy-tools. If the work is not carefully smoothed with the point-tools, previous to finishing, it cannot be accurately measured, and therefore the proper amount to be left for finishing with the spring tools cannot be easily determined.