Details of forging are now resumed. Angular keys are much more valuable, and more extensively used, than round ones, because, by proper forging, they may be made to fit their respective key-beds, so that, by a small amount of filing, the key may be reduced to enter the key-bed the whole distance required. The thinnest kind of angular keys is named flat, because the width of it is greater than its thickness, and not because it is very flat or true in any way, great numbers of them being used as they are forged, without any filing. Flat keys are made with heads, when the head will be required for unfixing the key. But when the head is not required, the keys can be made from a bar at a much quicker rate. Flat keys may be short and thick, or long and slender. They may have screws at the ends, or small pin-holes instead, as shown by No. 5, Plate 1. A flat key of this kind can be easily forged by a learner who has had a little practice ; but the handling and forging of the round key is more instructive, because it compels the learner to strike carefully to prevent the disfigurement of his work. The smallest kind of flat keys are used for small joint-pins or ends of small bolts. A key-way is cut through, near the end of the joint-pin or bolt; and the small flat key is placed in the key-way so that the thin part of the key-stem is at right angles to the stein of the joint-pin or bolt. This allows great strength to the flat key, without making a large key-way to weaken the bolt. The key is fitted tight against the washer, or against the outside of the nut, as represented by Figs. 73 and 74.

To forge a key suitable for a joint shown by Fig. 73 or 74 but little labour is necessary, unless the steel or iron from which the key is made happens to be much larger at the commencement of the forging. This will often be the case with makers of small work, and private individuals, who are bound to make use of remnants of various dimensions, in an economical manner. In such circumstances, when a number of keys are required at one time of several sizes, it is usual to first draw down the steel to the largest size required, and make that number of keys required of the largest diameter, next draw down the steel to the second size, and afterwards draw to other dimensions required.