The nuts here referred to are those by which the valves are attached to their respective slide-rods. A nut of this class is termed a tee-nut, through resembling a letter T; it is made of gun-metal, and furnished with a thick flange similar to a bolt-head. The nut is represented by Fig. 963, and in Fig. 964 a slide-rod is shown having a tee-nut attached to its end. In the slide-valve to be connected is a tee-shaped recess for containing the nut, and the mode of connecting the rod to the nut consists in forming a screwed hole in it, and forming a screw upon one end of the rod to fit.

The tee-shaped recess in a slide-valve is deeper than the nut intended to be therein, and at the first fitting of them together, the nut is situated at the bottom of the recess. Therefore the valve-nut is allowed a free movement from the bottom of the recess to its mouth, and, consequently, when all are connected together, a free movement of the valve towards the cylinder is allowed without straining the rod or packing apparatus. Also, at a future time, the faces of the valve and cylinder can be reduced for repair, without requiring alteration of the rod's relative position. By thus providing a space for the nut and valve to shift their relative positions, the necessity for providing a space in the rod's joint-gap is usually obviated ; but this space also is sometimes provided.

The mode of properly fitting a tee-nut to its rod and valve consists in first drilling and screwing the nut and screwing the rod's end to fit, previous to finally fitting the nut to the recess in the valve. If the rod is only about an inch in diameter, its nut can be drilled and tapped at the first beginning of its treatment; but a large nut requires to be first flattened on one or two sides, because it may then be quickly fixed upon a lathe-chuck, this being required for effecting the screwing.

After the nut, whether small or large, has been fitted to the rod's screwed end, it can be properly lined in order to accurately shape it, so that its sides shall be parallel with the rod's length, and its bottom or flange-part shall be square to the rod's length. To make the shoulders or bearing surfaces square, the nut may be put upon a nut-arbor and partly turned, the parts not turned being afterwards made true with chipping and filing. The nut can also, in some cases, be turned while on its slide-rod, instead of on an arbor. The right-angular surfaces required for the nut can also be indicated by lining, and entirely produced without lathe-turning. For this purpose, the slide-rod having its nut screwed on, is put upon vee-blocks on a lining-table, and the nut is lined with a scriber-block. As soon as the rod's length is adjusted to parallelism with the table, the scriber-point is adjusted to a proper height to mark lines upon the nut to indicate those surfaces to be parallel with the rod's length. In order to scribe the lines to show the right-angular surfaces or shoulders of the nut, it is only necessary to place an el-square upon the table with the blade in contact with the nut, and scribe lines along the blade's edge with a scriber. This latter marking is done while the rod yet remains in the same position on the vee-blocks as at first arranged. The scribing of these lines, which denote the nut's shoulders, is of course not required if the nut is turned, as stated, on an arbor. A slide-rod in position on vee-blocks is shown by Fig. 965. ,

When a tee-nut has been lined and regularly reduced to the lines, by means of filing, if small, or a planing-machine if large, it becomes a sort of gauge by which the recess in the valve can be chipped and filed if necessary. The principal bearing surfaces are the shoulders; and these must be carefully made to bear equally upon the surfaces of the recess ; if not, the action of the rod to and fro in ordinary work, will in time break the rod or do other mischief. Steel slide-rods are often broken at their thread-junctions by reason of improper fitting.