The apparata required for planing screw-nuts, after they are screwed and turned, are shown by Figs. 733, 734, and 735. Fig. 733 denotes a nut-mandril or nut-spindle; this consists of a steel spindle which is smoothly lathe-turned parallel in its mid-portion, to fit the screwed holes of nuts of one size. The spindle has a collar at one end solid with the remainder, and a screw at the other end which fits a screw-nut. That shoulder of the collar which joins the middle parallel part is also smoothly turned, to make it right-angular to the length of the spindle, and the collar may be either cylindrical or hexagonal, as seen in the Figure, the six-sided shape being principally useful for large spindles, that they may be easily rotated with a spanner. When a nut-spindle is to be used, several nuts are slid thereon, and all are firmly fixed together, and against the collar's shoulder, by tightly screwing the nut belonging to the spindle. When it happens that the spindle-nut will not grip the nuts to be planed, through the end of the spindle-screw being too near the hole of the outer nut, the fixing-nut is made to bear against one or two packing-rings of iron, and if thus fastened they appear as in the Figure (734). These rings are termed washers, and six or eight are sometimes used on a nut-spindle, when it happens that only one or two nuts are to be planed at that particular time. There is also another sort of packing used for nut-spindles, and it consists of tubular pieces of thin sheet brass, or tinned iron. Such packing-pieces are made to fit each other, so that any tubular piece will tightly slide into the one which is of the next size larger, that two or three may be at one time on a spindle, the smallest one being in immediate contact with it. The length of such tubes is about equal to the length of that portion of the spindle for which they are made; and the packing is required to adapt the parallel part of a spindle which is too small for the nuts to be planed without such packing. Consequently, one nut-spindle may be thus made to fit several sizes of nuts, instead of one size only.

After the nuts are slid along the spindle, the washers and spindle-nut attached, also a circular divider-plate keyed upon one end, the spindle is put between poppet-screws, and appears as in Fig. 735. For small spindles, such as those for planing nuts belonging to bolts not more than an inch thick, the poppets are fastened to a planing-table with nuts beneath, this arrangement is denoted in the Figure (735). For large nuts, the spindles are supported with a couple of strong standards or supporters, having broad bases or feet, and these are bolted to the machine-table with screw-bolts and nuts, the bolts being put through the feet of the standards and also through the table near its front edge. Holdfast plates also, are sometimes used, their paws being placed upon the standards' feet. In order to properly fix poppets so that the poppet-screws shall be in line with each other, the planed ends of the standards' feet are adjusted to some of the straight lines on the table's face, this adjustment being effected previous to finally tightening the holding-bolts. The divider-plate or disc, is shown attached to a spindle in the Figure, and the diameter of the plate is of little importance, except with regard to convenience and lightness; it is, however, accurately marked, so that six holes can be bored at equal distances apart near its rim, s shown, in order to admit the point of the fixing-pin, which also is shown. While the spindle is on the poppet-screw points, the nuts to be planed are finally put into order by gentle hammering, to make all their upper surfaces parallel to the table, which is done after partly tightening the fixing-nut, and also after the fixing-pin is driven in ; and when properly adjusted, the fixing-nut is thoroughly tightened to prepare for planing

The planing of nuts thus arranged on a spindle, is done with ordinary facing-tools; and the six outer planes of the nuts are made equi-distant from the hole, as required, by the rotation of the spindle. Such rotation commences after one slice is cut off all the nuts, the fixing-pin being now taken out, and the spindle moved a sixth part of a complete rotation, which places another of the divider-plate's holes opposite the fixing-pin's point; the pin is therefore again driven in, to fix the nuts for planing a slice from the next lot of nuts' faces. When one slice is cut from these, the spindle is again shifted to place the pin into the next hole, for planing the third lot of sides or faces; and such rotation is continued until all the six sides have had one slice removed. All the sides are thus planed while the tool-point is at one height from the table ; therefore some of the first slices cut off will not in any way affect some of the sides, unless the holes in the nuts happen to be exactly in the middle before planing. After the first planing, the tool is therefore advanced downwards a short distance, to cut off another slice from all the sides, by gradual rotation of the nut-spindle as before. The exact dimensions of the nuts, is ascertained either with an outside calliper, or with a gap-gauge, which is easily applied to the two opposite sides previous to adjusting the tool for taking off another slice. When the nuts are very nearly finished, they are polished, when necessary, by cutting off only a very thin slice, the same facing-tool being used for finishing, which was used for roughing, with the difference of having the tool's point sharp and slightly curved, while smoothing is effected. During this smoothing, soapy water is applied, if polishing is intended.

In cases of emergency, it may be necessary to plane a few large nuts for which there is no spindle. In such cases the nut or nuts, after being lathe-turned, are fixed to an el-chuck in the position shown in Fig. 736, resting on a packing-block situated on the planing-table, the nut being held to the chuck with a bolt, nut, and washers. Previous to placing the nut for planing, its hexagonal shape and dimensions should be marked upon one of the turned faces, the centre of the face being found by fixing a piece of wood in the screwed hole. Another mode of scribing, is effected by first making a circular line on one face with a tool-point, while the nut is in the lathe. This line is a circumference of the desired diameter, and is divided into six, to delineate a hexagon in the usual way, which is of the required size. Being scribed, the nut is adjusted while against the el-chuck, by applying the scriber-block's point, the nut being gently hammered until the upper scribed line is seen to be parallel to the table-face, this parallelism being discovered by applying the scriber-point to both ends of the line. When parallelism is obtained two more holdfast plates are attached, one at each side of the bolt shown in the Figure, and when all are thoroughly tightened, the planing of the upper side proceeds with ordinary facers, until the nut is reduced to the upper scribed line; after which, the nut is again adjusted, by means of another line, and again planed. Six fixings of this character are necessary to complete the planing of the nut. The length of the el-chuck, to which the nut is bolted, may be situated either at right-angles to the length of the planing-table, or parallel with it, this being the position of the one in the Figure.