_Answer._ “_Setting out packing_” is simply expanding the rings when they get too loose. With ordinary spring packing, figs. 96 and 97, which is now generally used, this is done by screwing up the nuts _b_, _b_, _b_, which, as was explained in answer to Question 169, compresses the springs _a_, _a_, _a_, and thus expands the rings _A_, _A_. In doing this, as already stated, great care must be exercised not to screw the nuts up too hard, and it is always better to have the packing too loose than too tight. Care must also be taken to keep the piston-rod in the centre of the cylinder, otherwise there will be undue pressure and wear on the stuffing-box. After the nuts are screwed up, the position of the piston-head should be tested with a pair of callipers. This is done by placing one leg of the callipers against the side of the cylinder, and setting them so that the other leg will just touch the edge of the projection _E_, fig. 96, or the end of the piston-rod. Then by placing the callipers above and below, and on each side of the piston, it will appear whether it is too high or too low or too near either side; then by loosening the nuts on one side and tightening them on the other it can be moved to a central position. Ordinarily this work is intrusted to persons who are employed for the purpose. A young locomotive runner, fireman or mechanic will, however, always do well to familiarize himself with such duties, and, if possible, do it himself, under the direction of those who are skilled in that kind of work. QUESTION 463. _If the stuffing-box of the piston-rod leaks, what should be done?_ _Answer._ If the packing in it is in good condition, it can usually be made tight by simply screwing up the gland. In doing this, the nuts on the bolts should not be screwed up more than is necessary to make the packing steam-tight. Any greater pressure only increases the friction on the piston-rod unnecessarily. In doing this, the two bolts must be screwed up equally, otherwise the gland will be “canted,” that is, inclined so as to “bind” or bear unequally and very hard against the piston-rod, and thus be liable to cut or scratch it. After packing has been in the stuffing-box a long time, it becomes very hard and compact, and sometimes partly charred. Then either it must be removed and new packing be put in, or, if in tolerably good condition, it can often be made to work well by simply reversing it, that is, by putting that which was at the bottom of the stuffing-box on top and _vice versa_. Before packing is put into a stuffing-box, the former should always be thoroughly oiled. QUESTION 464. _When the slides of the cross-heads wear, how is the lost motion taken up?_