It is now needful to consider the treatment of several sorts of rods and bars in connexion with their respective joint-pins, brasses, and other portions belonging to them.

Joint-Parts Of Slide-Rods And Connecting-Rods

The joint-ends of small rods and bars in general should be made of steel, and be hardened, to obtain great durability. Large rods also should have steel joints, supposing that the maker has arrangements for making them. It is therefore, in most cases, convenient to make an entire rod or bar of steel, to avoid the attachment of steel ends to an iron mid-portion.

Excellent joint-parts are produced by a final process of hardening, after an accurate shaping and fitting of a steel joint has been effected. But because of such portions being liable to break during the cooling, it is usual to harden only comparative small pieces, and to allow large objects to remain soft.

The gap in the joint-end of a slide-rod is usually so made that the gap is larger than the end-boss of the rod which is to fit. The joint-nut or other joint-part, which is secured to the slide-valve, is furnished with a gap of sufficient size to allow an eighth or a quarter of an inch of room between the slide-rod boss and the side of the joint-gap, when both are connected. In Fig. 962 a gap having an amount of room for this purpose is shown. Such a space provides for the future wear of the slide-valve face, and also of the cylinder face ; so that at a future time the friction surfaces can be reduced and flattened without interfering with the relative position of the slide-rod in its packing-box and gland.