A stud is a permanently fixed bolt without a head, and is fixed either by a conical portion in the middle or at one end. Studs intended for joint-pins or pivots are screwed at one end; and screwed at both ends if intended for connexions for cylinder lids, slide-jackets, and similar work.

Pivot-studs are made of tough, fibrous iron or steel, to resist the side strains continually imposed during use. A pivot-stud is shown by Fig. 21. That part of a stud intended for a joint-pin or pivot of any kind requires good welding and closing by the angular-gap rounding-tools, which facilitates the production of a smooth surface for friction. A close texture is necessary for those parts of studs or pins intended for wear, whether soft, hard, or case-hardened. The conical part of a stud may be more fibrous than the parallel portion, which will be subjected to continual abrasion while in use. The screw part, also, must be welded to a depth which is rather greater than the depth of the intended screw-thread. Studs, which are represented by Fig. 21, frequently need drilling and screwing at the centre to admit a small bolt for fixing a washer. The place of the washer is indicated in the Figure by W. Much trouble will arise in drilling and screwing the hole if the metal is not welded in that part; consequently, the smith obtains the requisite solidity by upsetting and rounding the work while at a welding heat.

The screw-pin or screw-pivot, shown by Fig. 22, is quickly forged by reducing, with a fuller and steam-hammer, a bar or rod which is the diameter of the intended pin-head. A portion of the stem of the pin is parallel, and a part is conical. This conical part is that which holds the pin in its place while in use, and should be soft and fibrous.

Iron and steel studs, of all classes, are in condition to wear properly, with but little friction, if hardened. For this reason, attention to the forging and quality of the iron or steel from which they are made is necessary to ensure a good friction surface. The careful labour of the turners and grinders will be of little service if the metal contains cracks, small openings, or other defects arising from careless forging. Such blemishes seldom appear till the work is turned by the lathe nearly to the desired diameters, so that much time is consumed in the turning of articles that are discovered to be unfit for their uses. Such errors in forging arise from the smith considering merely the simple appearance of the article he is about to make, and not, at the same time, reflecting or inquiring concerning the particular uses to which his work will be applied. Many forgings of importance are entrusted to unskilful men, because the outside appearance of the forging is of simple character, and the result, in many cases, involves a consumption of twice the amount of time that should be employed. A good smith is also a man of experience in general mechanical affairs; without such experience he cannot produce good work, however skilful he may be, except he happens to be working under a man who is able to tell him what to do, and also able to tell him how to do it. The smith must know, at the time of commencing to forge the article, the amount and character of the wear and strain to which his work will be subjected, and whether the work will be exposed to destructive chemical action in addition to friction, side strains, and abrasion.

It is only by such foreknowledge that a smith becomes a really valuable man - one who is able to produce solid work, and to select the class of metal adapted to the requirements. Such a man will not cut a piece from a straight bar of iron or steel and name it a forging, merely because the outside shape of the piece cut off corresponds to the outside shape of the forging desired. The internal structure may be different to the structure necessary; and is often discovered after several hours of fining, centring, planing, turning, and screw-cutting. Every operation may progress favourably till the screw is being made, which is often the last process; and if the portion intended to be formed into a screw is not welded, it will tumble off while being screwed, and the elegant piece of turning and screw-cutting becomes fit for the scrap-heap.