Another cause of failure is the too free use of borax. If too much is used, it melts and runs about in the fire, unites with the dirt, and generally blocks up the nozzle of the blast, causing a great deal of trouble to dislodge. If the blast is not sufficient, then less heat is generated than is necessary, and it is impossible to form a good weld unless sufficient heat is applied. Steel axles do not find great favour with the trade, although a large quantity of them are used. They are unreliable, breaking and fracturing without a moment’s warning, whereas an axle of faggoted iron would only twist under the same circumstances, and could easily be re-forged and set right again. _Setting Axles._ Setting axles is giving them the bend and slope required, in order to fall in with the principles of the dished wheel. It is chiefly applied to the axle-arm, and this is the most important part, setting the beds being mere caprice. The great object to be obtained is, to give the arm the right pitch every way, to make the carriage run easy and as light as possible, even in the absence of a plumb spoke. All carriages do not look best, when running, with the bottom spoke plumb or vertical. In some of the heavier coaches or carriages more slope or “pitch” has to be given to the arm to carry the wheel away from the body, so as to bring them to some specified track, in order to suit some particular customer, so that we must be governed by circumstances. There is a patent “axle-set,” but it is not of much assistance, for half the smiths know nothing about it, and if they did it would not be generally used, as the advantages derived from its use are not equal to the trouble of using it. Besides, the wheels are not always dished exactly alike, and it would require adjusting to each variety of wheel; and again, the wheels are not always (though they ought to be) ready; and when the smith knows the sort of vehicle he is working upon he can give his axles the required pitch, within half a degree or so, and the patent axle-set is, unfortunately, not capable of being adjusted to an idea. [Illustration: Fig. 21.]