Sheet metal work

The importance of sheet-metal work in modem manufacturing developments is vastly greater than those not actually in touch with the work would imagine. Its use in building skylights, roofs, and cornices are visible and obvious applications of the industry, but there are countless operations in pressed metal manufacturing where the principles discussed herein find their most important application, and it is to help those who are actually working in this field that this volume has been printed. The sheet-metal draftsman has a very different problem in many respects from that of the mechanical draftsman. The mechanical draftsman has to deal, in the main, with square or circular shapes, and he has perfectly definite plans or elevations to fashion from the specifications given. His surfaces also are flat, spherical, or cylindrical and will be shaped by the various machines found in a well-equipped machine shop.

The sheet metal draftsman, on the other hand, must have a deeper understanding of geometrical principles, of the areas of surfaces, and many other matters not considered by the mechanical draftsman. He must be able, in addition to the simple drawing of the object, to make accurate developments of complex surfaces and do this so accurately that the sheet-metal form, made from his drawing, can be put together without waste and without distortion of the shape intended.

The author of this book has had years of practical experience in sheet metal work of all classes as well as abundant opportunity to apply his experience in teaching the subject. All the studies worked out are typical and the details are so clearly presented as to make the volume valuable for the beginner as well as for the most experienced metal worker.

The Sheet-metal worker of today who wishes to succeed must know far more than was necessary years ago. There are many good, practical sheet-metal workers in the trade who are handicapped because they are unable to lay out the patterns that arise in their daily work. Notwithstanding the introduction of labor saving machinery, the demand for good workmen has increased. While most sheet-metal workers acquire practical knowledge in the shop, they lack the technical education necessary to enable them to become proficient as pattern cutters and draftsmen. In this course, special attention is given to the fundamental principles that underlie the art and science of pattern drafting.

Practical workshop problems will be presented, such as arise in everyday practice, thus giving the student the practical experience that usually comes only after long association with the trade.


CONSTRUCTION

In constructing the various articles made from sheet metal, various gauges or thicknesses of metal are used. For all gauges from No. 20 to No. 30 inclusive, we assume in the development of the pattern, that we are dealing with no thickness, and we make no allowance for bending or rolling in the machine. But where the metal is of heavier gauge than No. 20, allowance must be made  for shrinkage of the metal in the bending find rolling operations, \ which will be explained in connection with development in heavy sheet-metal work. Certain instructions for wiring, seaming, and transferring patterns are not given here as they more properly belong to tinsmithing work. It is sometimes the case that the capacity of a vessel or article must be determined, when the rules given in Mensuration should be followed. When figuring on sheet-metal work, the specifications sometimes call for various metals, such as galvanized sheet iron or steel, planished iron, heavy boiler plate band iron, square or round rods for bracing, etc., zinc, copper, or brass; and the weight of the metal must often be calculated together with that of stiffening rods, braces, etc. On this account it is necessary to have tables which can be consulted for the various weights.


PATTERNS OBTAINED BY VARIOUS METHODS.

In this course will be explained the four methods used in developing patterns for sheet-metal work, namely, parallel line, radial line, triangulation, and approximate developments. Furthermore, practical problems illustrating these methods will be carefully worked out in every detail.