The consumer must decide which; if he wants sharp angles he must accept the fin and cut it off, or have it cut off by the manufacturer.
Rivet-steel should be tested rigidly for red-shortness, because red-short steel may crack under the head as the steel cools.
Emphasis is laid upon this because engineers will insist upon excessive ductility in rivet-steel, not realizing that they may be requiring the manufacturer to overdose his steel with oxygen to its serious injury.
No sharp re-entrant angles should be allowed under any circumstances where there is a possibility of vibrations running through the mass. All re-entrant angles should be filleted neatly.
No deep tool-marks should be allowed; a fine line scored around a piece by a lathe-tool, or a sharp line cut in a surface by a planing-tool will fix a line of fracture as neatly as a diamond-scratch will do it on a piece of glass.
Indentations by hammers or sledges should be avoided; they may not be as dangerous as lathe-cuts, but they can do no good, and therefore they are of no use.
XIV.
HUMBUGS.
Steel is of such universal use and interest in all of the arts that it attracts the attention of would-be inventors perhaps more than any other one material.
Half-informed, or wholly uninformed, men get a smattering of knowledge of some one or more of the well-known properties of steel, make an experiment which produces a result that is new and startling to them, and at once imagine that they have made a discovery; this they proceed to patent and then offer it to the world with a great flourish of trumpets.