Tool steel

“ For centuries the secret art of making tool steel was handed down from father to son. The manufacture of tool steel is still an art which, by the aid of science, has lost much of its secrecy; yet tool steel is today made by practical men skilled as melters, hammer-men, and rollers, each knowing his art. ”

“ The manufacture of high-speed steel represents the highest art in the making of steel by tool-steel practice. Some may say, on account of our increased knowledge of chemistry and metallurgy, that the making of such steel has ceased to be an art, but has become a science. It is, in fact an art; aided by science. The human element in its manufacture is a decided factor, as will be brought in the following remarks:
The heat treatment of steel in its broad aspect may be said to commence with the melting furnace and end with the hardening and tempering of the finished product. ”

“ The highest grades of tool-steel are improved by being kept in stock for a considerable time, the longer the better. It seems that bayonets, swords, and guns are liable to changes which may account for failure under sudden thrust or strain. Gauges of tool steel, which are required to be hard in the extreme, are finished to their standard sizes a year or two after the hardening process. Slow molecular changes register themselves in altered dimensions. In the Bureau of Standards at Washington are a yard in steel and a yard in brass, at first identical in length ”

“ It is possible to harden the surface of tool steel extremely hard and yet leave its inner core soft and tough for strength, by a process similar to case-hardening and known as "pack-hardening." It consists in using tool steel of carbon contents ranging from 60 to 80 points, packing this in a box with charred leather mixed with wood charcoal and heating at a low-red heat for 2 or 3 hr., thus raising the carbon content of the exterior of the piece. The article when quenched in an oil bath will have an extremely hard exterior and tough core. ”

“ In hardening high-speed tool steel, or air hardening steels, the tool should be handled as for carbon steel, except that after the body reaches a cherry red, the cutting point must be quickly brought to a white heat, almost melting, so that it seems ready for welding. ”

“ This alloy is so hard that it cannot be machined or drilled by ordinary means; it must be treated by emery or carborundum wheels. Yet it is so malleable that it can be used for rivets when headed cold. It is so tough that it may be bent and twisted at will without rupture, so that it forms railroad switches, frogs, and crossings of great durability.
High-Speed Tool Steels.
Until 1868, the steel tools used in lathes and drills, planers and so on, were limited to the moderate pace at which they remained cool enough to keep their temper. ”

“ Machined or forged steel parts are packed with case-hardening material in metal boxes and subjected to a red heat. Under such conditions, carbon is absorbed by the steel surfaces, and a carburized case is produced capable of responding to ordinary hardening and tempering operations, the core meanwhile retaining its original softness and toughness.
Such case-hardened parts are stronger, cheaper, and more serviceable than similar parts made of tool steel. The tough core resists breakage by shock. The hardened case resists wear from friction. ”

“ The steels that will harden (we will call them “carbon tool steels”) , range ordinarily from the .60 per cent carbon variety, used for hammers, cold chisels, etc., to those containing 1.50 per cent of carbon which are selected for razors, scalpels, and other tools requiring high temper. Each one of these many grades is susceptible of a wide variety of temper in the hands of a capable man, who must select his steel and give to it the most desirable temper for the work for which the tool is designed. ”

“ When taking heavy cuts a tool of to-day may exert as much as ten tons’ pressure against the metal it is cutting and the advent of this wonderful material for tools necessitated the building of immensely heavier and stronger lathes and other machines, which, alone, were capable of giving them power to do their work. The high-speed steels, therefore, have revolutionized metal-cutting practice and shop methods and have very largely aided efficiency. ”

“ While it has not displaced the crucible method for the production of steels of the very highest qualities, it has proceeded far enough in this direction in the very limited number of years 232since its introduction, that it is certain that the crucible, even for tool steels, is to have a keen competitor. Tool steels in considerable variety are to-day being quite satisfactorily made in the electric furnace and it is not at all unlikely that steels of the very highest grade will shortly be produced by this method. ”

“ Draw-filing.—Making six-sided and eight-sided punches and scratchawls out of hexagon and octagon tool steel is interesting work. The steel is cut to length by filing a crease all around with a three-cornered file. When it is sufficiently notched, the steel will break straight across. To shape the tool and to draw out the point the steel is heated in the forge to a dull cherry red and hammered carefully to preserve the shape along the taper. Special attention must be given to the numerous corners. A scratchawl or small punch, must be heated many times and hammered quickly before cooling. ”

“ All machinists know of certain brands of tool steel which they prefer. Tool steel is made especially for certain purposes; as for razors and surgical instruments, for saws, for files, for springs, for cutting tools generally. ”

“ In the school forge shop, the tool steel used should be of an inexpensive kind. High priced steel should not be used as more or less is wasted by the pupils in working. A carbon steel should be used for all forge shop tools. About 75 to 95 point is suitable. High-speed tool steel should be used only to give the pupils instruction in its handling and use, and to familiarize them with the different kinds of steel and their treatment. ”

“ It is indeed a pleasure to see the new type of machine tool operating with high-speed steel, and treating the work it has to turn out in such a businesslike way, throwing off shavings from steel and iron as one usually sees in turning wood, and imparting a life and energy to the whole establishment in remarkable contrast to the sleepy rate at which metals used to be turned and machined for so many years past, thus exerting an influence on everybody therein to get “a hustle” on that is positively exhilarating in its effects. ”

“ For light lathe work, high speed steel is used in the adjustable tool holder. The most common tool for doing heavy work is the round nose which is made from various size steel.
High speed tool steel is sold under many brands. The method of handling is about the same for all. However each manufacturer will give the method which is best for his particular make of steel. In forging high speed lathe tools, a furnace or clean fire with plenty of coke is used. ”

“ 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 ”

“ Tool steel should be held in a perpendicular position when it enters the water to cool all sides alike. Otherwise the new tool might warp. It is better to dip slowly, sometimes holding the point, or cutting edge, in the water while permitting the shank to cool slowly enough to remain soft. Some sizes of steel may be tempered too hard at first and the temper immediately drawn by permitting the heat of the shank to follow down almost to the edge, then dip. ”

“ For this purpose, of course, the highest grade of steel is a necessity, since flaws developed in rolling, as the result of “pipes” or “air-holes” in the original ingot, are liable to be both destructive to the efficiency of the tool and dangerous to human life. For several years, therefore, steel of the highest grade was imported from England, where it was produced under the greatest precautions known to science, at the direct order of the Simonds manufactory. ”

“ When the steel is forged or rolled this skin will be united firmly to the steel, and it will be thinner or thicker, according to the number of heatings and the time of exposure to the fire. In tool-making this skin must always be removed. Many an expensive tool is made perfectly worthless by not having this skin all removed, owing usually to mistaken economy. The steel is expensive, and the tool-maker does not wish to cut it up into worthless chips. ”

“ This type of tool has a flat or straight cutting edge at the end, and will leave a smooth finish even though the feed is coarse, provided the cutting edge is set parallel with the tool's travel so as to avoid ridges. Broad-nosed tools and wide feeds are better adapted for finishing cast iron than steel. When turning steel, if the work is at all flexible, a broad tool tends to gouge into it and for this reason round-nosed tools and finer feeds are generally necessary. ”

“ When the steel made from such iron is wrought into a tool and ground, the edge is uneven, serrated, softer in one place than another. This amounts to a fatal defect in those articles where great and uniform hardness is required, as in screw-taps, wire-drawers, plates, dies, and stamps for coining and engraving. It is evident, as the carbon is introduced from the surface, that there will be less in the middle than at the outside of the bars; thus the steel is not of a uniform character. ”

“ On ordinary machinery steel or nickel steel the temper can be drawn to a dark blue or up to 900°F. If the tool is of a special form or character, the risk of melting or scaling the point cannot be taken. In these cases the tool should be packed, but if there is no packing equipment, a tool can be heated to as high heat as is safe without risk to cutting edges, and cyanide or prussiate of potash can be sprinkled over the face and then quenched in oil. ”

“ Persons who have occasion to use tool or carbon steel now and then and do not have access to an assorted stock of this material find that the kind most readily obtained at the hardware store is the unannealed steel known as chisel steel. Machining or filing such steel is exceedingly slow and difficult, besides the destruction of tools ”

“ A further process is the manufacture of the metal thus treated into SHEAR STEEL, by exposing a fasciculus of the blistered steel rods, with sand scattered over them for the purposes of a flux, to the heat of a wind-furnace until the whole mass becomes of a welding heat, when it is taken from the fire and drawn out under a forge-hammer,—the process of welding being repeated, after which the steel is reduced to the required sizes. ”

“ They were tempered by heating to a dark red and left to cool in the air. The high speed steels of today are heated to 2,000° or 2,200° Fahr., or a white heat bordering on a welding heat.
The chemical composition of these new steels are only known by their makers. However, it is said that they contain carbon, tungsten, chromium, manganese and other elements.
The great advantage in using high speed steel, is that a machine can be run three times as fast as one [81] using carbon steel, without destroying the edge of the tool. ”

“ In the practice of many tool makers in the Eastern States the tool is ground to a point a, Fig. 932, that is, ground sharp and merely rounded off with an oil-stone. This may serve when the lathe has an exceedingly fine feed, and the strain being in that case very slight the tool point may be made to stand well above the level of the body of the steel, as in the figure, and thus save forging; but this is a slow method of procedure, and produces no better work than a tool which is rounded at the point, and therefore capable of producing smoother work with a much coarser feed. ”

“ On the other hand, it may be claimed that in the perfect welding due to the fusion of cast iron, the interposition of 10 or even 20 per cent. of impurities, such as carbon, silicon, and copper, does not affect the strength of the mass as much as 1 or 2 per cent. of carbon or copper affects the strength of a weld made at a plastic instead of a fluid heat. It is also true that high tool steel, containing 11⁄2 per cent. of carbon is much stronger throughout its mass, all of which has been welded by fusion, than it would be if it had less carbon. ”

“ Among the improved processes invented of late years for the manufacture of steel are those of Heath, Mushet, and Bessemer. The last promises to effect before long an entire revolution in the iron and steel trade. By it the crude metal is converted by one simple process, directly as it comes from the blast-furnace. ”

“ The total weight of the shipments on this contract was something like 23,000 tons, this figure including 7,500 tons of lumber. The other tonnage consisted of tubing of steel, brass, copper and alumi [Pg 242] num; sheets of steel, copper, lead, and aluminum; as well as bar steel, tool steel, structural steel, ball bearings, crank shafts, turnbuckles, radiator tubes, wire, cable, bolts, nuts, screws, nails, fiber cloth, felt, and rubber. All of this was in addition to approximately 1,000 machine tools, such as motors, lathes, and grinders. ”