When it is necessary to insert a nut into a circular recess, and to fill, or partly fill it, a circular nut is used, having holes bored into the outside face of the nut for fixing or unfixing it.

Circular nuts are also used for ornament, and to prevent contact with corners. Fig. 18 represents one of this class, having a flange, and holes bored around in which to place the end of a steel lever, named a tommy, by which the nut is fixed or unfixed.

The forging of circular nuts with flanges consists in drawing down or reducing a bar or rod which is of the same diameter as the intended flange of the nut. After being partly reduced to the finished diameter, the smaller part is made as solid as possible, by welding and hammering, to give the necessary strength to the nut while being punched. After it is welded, the proper quantity of iron to make the nut is cut from the bar and punched, and the hole then drifted to the required diameter. The rounding of the outsides is accomplished by rounding-tools, while the nut is upon a nut-mandril.

This method is economical if the proper length of iron is reduced, to avoid cutting off large scrap-pieces; and is always available with good, soft, fibrous metal, that will bear punching without splitting. The tongs for gripping the nuts while being punched is shown by Fig. 99.