Members when brought together to be riveted lip must have the holes in the different pieces exactly opposite so as not to require drifting in order to bring them together. When driven, rivets must completely fill the holes, and must be of such length that, when the head is formed, the pieces will be brought together under pressure. Rivet heads must be concentric with the axis of the rivet. Column ends or other surfaces specified to be faced must be brought to a true surface exactly at right angles with the axis of the member. All portions of the material not accessi ble after assembling must be painted before being assembled.
In inspecting cast iron, tests must be made to determine whether or not it conies up to the requirements of the specifica tions as regards quality. Inspection must also be made to see if the material is free from flaws such as blow holes, pockets of sand and unequal distribution of metal. Where the thickness cannot be measured readily as in the case of columns, small holes are bored to determine this. Where columns are east in a hori zontal position, as they generally are, the tendency is for the core to sag in the center, and therefore it is better to make this test near the center. A sharp blow of a hammer will often indicate unequal distribution of metal. A clear metallic ring indicates a thin shell and a dull heavy sound a thickness of the shell. If the edges are struck with a hammer and pieces fly off under the blow this indicates a brittle texture; a good quality iron should show only a slight indentation. Cast iron should be inspected also for straightness, accurateness of facing of bearing surfaces, and agreement with details. It is better to inspect cast iron before it is painted in order to the more easily discover flaws.
Relation of Engineer to Architect. An essential feature to be observed in all successful designing and detailing by the engineer, is co-operation with the work of the architect. This may seem to the student, at the outset, as a very simple point and one which will need little special attention. Yet the power to fully and quickly grasp the breadth of the architect's design, and its smallest details as well, and to make the structural design to fully harmonize with his work, will come only by persistent effort.
In some buildings, the work of the engineer, because of the character and purpose of the building, would determine conditions and features to which the architect must conform, but in general the reverse is true. For this reason the burden of harmonizing
his work is generally put upon the engineer.
He must see what has been established by the architect and how much he must vary the natural course of his design to con form to these conditions. He must often study long, over what at first seems scarcely possible to accomplish without clashing with the architect's scheme. In the working out of such details and problems, lie will need all his originality.
Interpretation of Drawings and Specifications. In prepar ing the working drawings, the draftsman generally has to do with the design of another. To this extent, therefore, he is not respon sible for the harmony of the design with the work of other lines. He is, however, responsible, if such a conflict of design escapes him, for it will be a sure indication that he has not looked at his problem from all sides, and in the light of later and more definite information which was, perhaps, lacking when the design was first made.
In working up the shop details, the draftsman must start with the question constantly in his mind, " How do I know?" He must not fix a measurement, nor establish the position and relation to other parts of a single piece, unless he finds concrete authority in the shape of plans, specifications, or written directions for so doing. Further than this, lie must determine that all the infor mation so given is in agreement, for he will be held responsible for failure to discover such disagreements.
There is a great tendency among those young in experience to be guided by what appears to be indicated. Drawings are not always made to exact scale and the structural draftsman should never establish anything by scaling without explicit directions for so doing, and should then make a written record of what has thus been established. • One of the most important instructions winch can be given a draftsman, is never to jump at conclusions. Have direct authority for all that is done and be sure your authority is not contradicted in some other place. Oral instructions should be at once written clown, as when once followed, they may become a necessary factor in other work. If information is lacking or there is a conflict, however small, in any of the information which is the basis and authority for your work, refer it at once to some one above you who can carry it to the one in authority.