FINISH AND GENERAL CONDITIONS.
As there can be no such thing as exact work done, there must be some tolerance as to variation in size. In standard sections, sheets, and plates this is usually covered by a percentage of weight; in forgings or any pieces that are to be machined the consumer should allow enough to insure a clean, sound surface. But it would be unwise to lay down any rule here, because conditions vary; a rolled round bar may finish nicely by a cut of from ¹/₃₂ to ¹/₁₆ of an inch, and so also a neatly dropped forging; an ordinary hammered forging might require a cut of ¼ or ⅜ of an inch; such a forging might be made closer to size at a cost for extra time at the hammer far exceeding the saving of cost in the lathe. These are cases where common-sense and good judgment must govern.
Pipes should not be tolerated if they can be discovered; because a pipe appears small in the end of a bar it is no evidence that it is not larger farther in.
Seams should not be allowed in any steel that is to be hardened; they should be a minimum in any steel, as they are of no possible use; small seams when not too numerous may do no harm in structural or machinery steel, and consumers should be reasonable in regard to them, or else they may have too high prices put upon their work, or too high heat used in efforts to close the last few harmless seams.
Burns, rough, ragged holes in the faces or on the corners, are inexcusable and should be rejected; the steel has been abused, or it is red-short; in either case the ragged breaks are good starting-points for final rupture.
Laps should not be permitted; they are evidences of carelessness; there can be no excuse for them.
Fins are sometimes unavoidable in a difficult shape; for instance, if a trapezoid is wanted, it may be rolled in this form:
or in this:
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.
Many steel-workers, even men of skill, who know something of the difficulties that follow irregular work, or who are not quite fully informed as to the properties of steel, seize upon these discoveries in the hope that they have found a royal road to success where all old pitfalls are removed and their path is made easy.
Not wishing to discourage pioneers in legitimate efforts to improve, it is the object of this chapter to warn them against being too ready to spend their money because of flaming circulars or glib tongues. It is the duty and the interest of a steel-maker to examine and test every apparently new suggestion, for the reason that there is still room for improvement, and he should let no opportunity for a betterment slip past him.
As a rule the steel-maker does test every claim that is laid before him, unless it be a repetition of some old plan long since tried and found worthless. This is the bane of the steel-maker’s life, and yet he must keep at this work so that he may know for himself whether anything of value has been discovered, and also that he may advise his clientage properly.
Inventions relating to the manufacture of steel have no interest for steel-users except as lively manufacturers may adopt the mistaken plan of flourishing trumpets to attract trade, not always giving a corresponding benefit to the consumer.
Examples of this sort of thing may be illustrated by so-called phosphorus steel, silicon steel, and aluminum steel; also the case mentioned before of parties recommending seams as evidences of excellence in high steel. Such efforts are sometimes costly to consumers until active competitive manufacturers expose the humbug.
Among the most absurd of such claims are those where a nostrum is used to convert ordinary Bessemer or open-hearth steel into the finest of tool-steel, equal to the best crucible-steel; for example, a patent to convert mild Bessemer steel into the finest tool-steel by merely carbonizing it by the old cementation process; this takes no account of the silicon, manganese, oxygen, and nitrogen in the mild Bessemer, makes no provision for their removal, and involves a costly method of putting carbon into poor stock in face of the fact that a Bessemer steel maker can put the same amount of carbon there at practically no cost, and so produce a better material.
Among the humbugs that do not involve the manufacturer, the pet one is a nostrum for restoring burnt steel; these have been evolved by the dozen, in face of the fact that burned steel cannot be restored except by smelting, and that overheated steel, coarse-grained steel, can be restored by merely heating it to the right temperature, a process which has been explained fully in [Chapter VI].
Another pet is some greasy compound for toughening high steel so as to make it do more work. This is done by heating the steel to about recalescence and plunging it into the grease, perhaps once, or possibly two or three times; then working it into a tool and proceeding in the ordinary way. This will make a good tool; it is the partial annealing plan explained in a previous chapter. Now take a similar piece of steel, heat it the same way, lay it down in a warm, dry place alongside the forge-fire, and let it cool; then heat it and work it into a tool and it will beat the greased tool.
When all of these operations of restoring, partial annealing, annealing, etc., depend merely upon temperature and rate of cooling, why spend money for nostrums that add no possible benefit?
There is room for improvement in steel, great room for great improvements; they will come in time as science and knowledge advance, and great benefits to the consumers will come with them.
This chapter is not written to place difficulties in the way of legitimate improvement, but to warn unsuspecting people against quackery. Some of the humbugs are honest productions of well-meaning ignorance, and some that come from designing manufacturers are not entitled to such charitable designation. A knowledge of the simplest properties of steel will enable a thoughtful man to judge as to whether a proposed improvement is likely to be of any value or not, and the warnings given are intended as a protection to the unsuspecting and credulous.
XV.
CONCLUSIONS.
After perusal of the preceding chapters the reader may form a hasty conclusion that if steel be so sensitive as it is stated to be its use may be difficult and precarious, and that it must be handled in fear and trembling, lest the result should be a dangerous structure, and the builder must be in doubt as to its safety.
The conveyance of any such impressions is not intended at all; emphasis has been laid upon practices that are hurtful in order that every steel-user may know what to avoid, solely that he may then be sure that he has the best, the most reliable, and most useful material that is known to man.