A couple of brasses which are tightly fixed in their boss can be bored either while they yet remain in the boss, or after they have been removed and again fastened together by some means. If they are to be bored while in their boss, the key-way and key are partly fitted that there may not be any risk of the brasses shifting while being bored. The boring of such is executed with a boring-machine or driller, and the holes are easily bored square to the lengths of the rods, as required, by adjusting the lengths of the rods to parallelism with the drilling-table. If brasses are bored in this manner, considerable care, good boring-rods, and good cutters are requisite to produce smoothly-formed parallel holes of the exact diameters required, and to properly curve the edges of the holes' entrances. When a number of brasses are to be bored to the same diameter, the boring can be completed with a good rosebit.

If a number of boss-brasses of several sizes are to be bored, a lathe should be used. A lathe will easily produce any exact diameters required for any number of holes, by using the ordinary slide-rest boring-tools, although the brasses cannot be so firmly held while on a lathe as while tight in their rod on a drilling-machine.

After a pair of brasses have been exactly fitted into their boss, and the circular lines for boring also correctly placed while in the boss, the brasses must be driven out and fastened together again, if a lathe is to be used for boring, and must be so fixed together that they shall be while out of their boss as near as possible in the same relative position to each other as when in the boss. To facilitate this refixing accurately together, a couple of cross-lines are scribed upon the ends of the brasses, which surfaces are plane and level with the boss-face, as before directed. This scribing is done while the brasses are tight in their places; the lines should be thin and well defined, that they may be easily referred to afterwards when being fixed together. The brasses are next driven out and fastened together with clamp-plates and screw-bolts, either two or four plates being used, according to the size of the brasses. When bolted together, they are gradually shifted into the proper positions by hammering them with wood blocks. To effect this, two things must be referred to; these are, the cross-lines which were marked while the brasses were in their rod or bar, and the plane smooth surfaces termed the ends of the brasses. They are therefore adjusted while on a surface-table, one smooth end being in contact with the surface, and the other end, on which the gauge-lines are scribed, being upwards. In this position they require hammering downwards to keep the bottom ends in close contact with the table, and they require hammering sideways to adjust the brasses until the cross-lines are seen to coincide as when they were first marked.

As soon as the cross-lines are put right, the circular lines also are by the same act put into order, and the brasses are ready for being fixed on a lathe-chuck to be bored. This is effected with a thin boring-tool, if the hole is small, and with a strong corner-tool if the hole is large. Care is necessary during boring to avoid shifting the brasses, because they cannot be bolted together very tightly without squeezing them out of shape, and because the faces of the brasses in contact are but small; consequently but little adhesion can be expected. These faces must be thoroughly clean, and not be in any case convex, but may be slightly concave, to prevent slipping; they may also be dusted with flour emery previous to fixing them together.

While the brasses are attached to the lathe in position for boring, they are held on a couple of parallel strips, or on a parallel ring, to provide a space for the tool's end, and also to cause the hole to be bored square to the ends of the brasses, and, consequently, square to the two faces of the boss belonging to the rod. The ends of the brasses are the only surfaces that can be referred to for obtaining the desired right-angular position with the lathe-chuck; therefore great care must have been previously exercised, during the fitting, to make the faces of the rod-boss parallel with the length of the rod, and to make the ends of the brasses parallel with the boss-faces.

Oil channels in the brasses just treated are similar in shape, and made by the same means as are adopted for the channels of strap-brasses; the round holes constituting the naves of the crosses, being either in the middles or sides, according to whether the connecting-bars or rods are to work with their lengths horizontal or vertical.