The iron for vehicle axles should be of the best quality. The method of working is as follows. A number of small bars are put up in a bundle sufficient to make an arm, and bound with iron rod to prevent falling about when working. The arm is then placed in the furnace, and thoroughly welded together. Whilst this is being done it is worked somewhat to the required shape. The collars are now made and welded on. For this purpose dies, or top and bottom tools, are used, the arm being worked at as great a heat as possible without burning, lighter heats being taken for finishing to the size required with light blows; afterwards turn and fit the axles. To case-harden, place the articles in an iron box or casing large enough to contain a packing of 2 in. or 3 in. of the hardening compound around each arm. The box should be sealed up air-tight at both ends. The compound generally used is leather shreds, ground raw bones, hydrocarbonated bone black, and sal soda, the whole being placed in a furnace and kept at a good heat for ten or twelve hours; then remove the articles from the box and cool out thoroughly. Where an extra hard casing is required the articles are re-heated, the box being filled with powdered potash and kept in the furnace until the potash is consumed.

Where large quantities of axles have to be cooled out the cooling tub should be arranged to have an inlet of cold water at the bottom, so that the water made warm by the work would flow out over the top, thereby ensuring a continuous cool supply. The collar plates are stamped out of No. 6 fender plate, and when solid flaps a re made in the axle, these plates have to be cut across one side to allow of bending back to get them on between the collar and the flap.