Shafting is nearly always cylindrical and made of wrought iron or steel. Cast iron is rarely used for shafting.

Axles are shafts which are subjected to bending without twisting.

The parts of a shaft or axle which rest upon the bearings or supports are called journals, pivots, or collars.

In journals the supporting pressure is at right angles to the axis of the shaft, while in pivots and collars the pressure is parallel to that axis.

Shafts may be solid or hollow. Hollow shafts are stronger than solid shafts for the same weight of material. Thus a hollow shaft having an external diameter of 10¼ inches and an internal diameter of 7 inches would have about the same weight as a solid shaft of the same material 7½ inches in diameter, but the former would have about double the strength of the latter. Hollow shafts are also stiffer and yield less to bending action than solid shafts, which in some cases, as in propeller shafts, is an objection.