EFFECTS OF BAD FITTING.
When the work of fitting a set of back-end brasses is completed, they should be put in the strap, and tried on the pin. If, after being keyed close together, they revolve on the pin without pinching, the fit is not too tight. It is of the greatest consequence, in fitting rod-brasses, to ascertain, beyond doubt, that the brasses have been bored out true, and that they fit in the strap so that the line of strain shall be in line with the cross-head and crank-pins. It occasionally happens, through bad workmanship, that when the back end of a rod is keyed up, and the front end not connected, the rod does not point straight to the cross-head pin, but in a line some distance to the right or left. The distance may be very small, yet sufficient to cause no small amount of trouble. By some pinching and jamming, a rod in this condition can be connected up; but it is almost sure to run hot. And a rod in this condition will never run satisfactorily till it is taken down and fitted by a competent machinist. The back end may be all right, and the forward end suffering from oblique fitting. This is even more common than the first case, and the effect is the same. A rod in this condition, besides displaying a tendency to run hot, will keep jerking the cross-head from side to side on the guides, and will probably make the cross-head chafe the guides at certain points. Rods never run cool, and free from jar, unless they are fitted to transmit the power in a direct line between the pins.