_Answer._ With rivets, which are made with a head at one end, and are inserted while they are red-hot into holes drilled or punched in the edges of the plates. After they are in the holes a head is formed on the other end, either with blows from hand hammers, or by a machine constructed for the purpose. In these machines the rivet after it is in the holes is brought between a fixed and a movable die, the head which is made with the rivet being placed against the fixed die, and the movable die is then pressed, either by steam or hydraulic pressure with great force against the other end of the rivet, thus forcing the end of the rivet into the form of the die, which is made of the proper shape and size for the rivet head. The powerful pressure which is thus brought on the rivet causes it to be pressed into all parts of the two holes, thus completely filling them both; whereas with hand riveting, the holes are not nearly so completely filled, as it is impossible with blows of a hammer to subject the rivets to so powerful or uniform a pressure as the machine brings upon them. [Illustration: _Fig. 53._] QUESTION 102. _What is the strength of riveted seams compared with that of the solid plate?_ _Answer._ The strength of a riveted seam depends very much upon the arrangement and proportion of the rivets, but with the best design and construction, the seams are always weaker than the solid plates, as it is always necessary to cut away a part of the plate for the rivet holes, which weakens the plate in three ways: 1. By lessening the amount of material to resist the strains. 2. By weakening that left between the holes. 3. By disturbing the uniformity of the distribution of the strains. The first cause of weakness is obvious from an inspection of an ordinary seam, riveted with a single row of rivets, fig. 53. In this we have two plates 7¹⁄₂ inches wide and ³⁄₈ thick fastened with four rivets ¹¹⁄₁₆ inches in diameter and 1⁷⁄₈ inches from centre to centre. The section of the plate calculated with decimals[29] would therefore be .375 × 7.5 = 2.81 square inches. A piece ¹¹⁄₁₆ inch wide and ³⁄₈ inch thick would be removed to form each hole, or a sectional area for the whole plate of .375 × .6875 × 4 = 1.03 square inches, so that the section of the plate would be reduced through the holes 2.81 - 1.03 = 1.78 square inches. In other words, on the dotted line _a b_ it will have only about 63 per cent. of the sectional area of the solid plate. [29] In the following calculations all the dimensions have for convenience been reduced to decimals.