Results are comparative. These facts are not mentioned to in any way belittle the value of the steel under consideration, but to show the reader that he should not get discouraged when he fails to get results paralleling those claimed by the makers of the steel. The only fair method of judging of the value of the steel to the individual is to test in comparison with the best tool he can obtain, from tempering steel. Because a tool will not stand up on cast iron running at 100 feet per minute, as claimed by the maker of the steel, is no proof the steel is no good. It might have stood all right at 90 feet, and perhaps a tool made from ordinary tempering steel might not have stood a speed of 30 feet; in which case the high speed steel was capable of doing more than three times the amount of work of the other. Many times a difference in cutting speed of only a few feet per minute will cause a tool to either stand well, or go down. There is no general set of instructions that can be given for working this steel, as a method that proved perfectly satisfactory on one would render another unfit for use. For instance, the writer at one time contributed an article to one of the mechanical journals on the subject of "High Speed Steel," recommending extremely high heats when hardening. Shortly after the appearance of the article a letter was received from a manufacturer of a brand of this steel, saying he had read the article with much interest and agreed with everything in it except the temperature necessary when hardening, as they had found their steel gave best results when it was hardened at a low cherry red heat. A trial of a tool which he sent proved it to be equal or superior to some that were hardened at the high heat mentioned. Follow maker's directions. To get satisfactory results with any brand the party using the steel should follow instructions sent with the steel as closely as possible. It is evident to the writer from results of his own experiments and the experience of others, that when this steel is thoroughly understood, results way beyond those we are at present getting will be obtained marvelous as they seem now. While the writer has made extensive experiments. with the steel under consideration, and has taken advantage of every opportunity to study its composition, this. study has been confined to printed statements made by those who claim to possess this knowledge. Knowing, however, that the successful man in any line of business is he who, by studious effort makes himself master of his subject,-what is more natural than that the student considering this subject should be anxious. to know the composition of this steel. The following is an abstract of a paper read by Mr. J. M. Gledhill before the "Iron and Steel Institute,” October, 1904: The high speed steels of the present day are combinations of iron and carbon with: (1). Tungsten, Molybdenum and Chromium. We will consider the influence of each of the elements entering into the various compositions. Influence of carbon A number of tools were made with the carbon percentage varying from 0.4 per cent. to 2.2 per cent. and the method of hardening was to heat the steel to the highest possible temperature without destroying the cutting Carbon and chromium edge, and then rapidly cooling in a strong air blast. By this simple method it was found that the greatest cutting efficiency is obtained where the carbon ranges from 0.4 per cent. to 0.9 per cent. and such steels are comparatively tough. Higher percentages are not desirable because greater difficulty is experienced in forging the steels and the tools are inferior. With increasing carbon contents, the steel is also very brittle, and has a tendency to break with unequal and intermittent cutting. Influence of Chromium Having found the best carbon content to range from 0.4 per cent. to 0.9 per cent., the next experiments were made to ascertain the influence of chromium varying from 1.0 per cent. to 6.0 per cent. Steels containing a low per centage are very tough and perform excellent work on the softer varieties of steel and cast iron, but when tried on harder materials the results obtained were not efficient. With an increased content of chromium the nature of the steel becomes much harder, and greater cutting efficiency is obtained on hard materials. It was observed that with an increase of chromium there must be a decrease in carbon to obtain the best results, for such percentage of chromium. Mention may here be made of an interesting experiment to ascertain what effect would be produced in a rapid steel by substituting vanadium for chromium. The amount of vanadium present was 2.0 per cent. The steel readily forged and worked very tough and was hardened by heating to a white heat and cooling in an air blast. This tool when tried on medium steel stood well, but not better than the steel with the much cheaper element of chromium in it. Other alloys. Influence of Tungsten This important element is contained in by far the greater number of the present high speed steels in use. A number of experiments were made with the tungsten content ranging from 9.0 per cent. to 27.0 per cent. From 9.0 per cent. to 16.0 per cent. the nature of the steel becomes very brittle, but at the same time the cutting efficiency is greatly increased and about 16.0 per cent. appeared to be the limit, as no better results were obtained by increasing the tungsten beyond this figure. Between 18.0 per cent. and 27.0 per cent. it was found that the nature of the steel altered somewhat and that instead of being brittle it became softer and tougher, and whilst such tools have the property of cutting very cleanly they do not stand up so well. Influence of Polybdenum The influence of this element is still under investigation and our experiments with it have produced excellent results, and is was found that where a large percentage of tungsten is necessary to make a good rapid steel, a considerable less percentage of molybdenum will suffice. A peculiarity of these molybdenum steels is that in order to obtain the greatest efficiency they do not require such a high temperature in hardening as do the tungsten steels, and if the temperature is increased above 1,800 degrees F. the tools are inferior and the life shortened. · Influence of Tungsten with Molybdenum It was found that the presence of from 0.5 per cent. to 3.0 per cent. molybdenum in a high tungsten steel slightly increased the cutting efficiency, but the advantage Influence of silicon. gained is altogether out of proportion to the cost of the added molybdenum. Influence of Silicon A number of rapid steels were made with silicon content varying from a trace up to 4.0 per cent. Silicon sensibly hardens such steels, and the cutting efficiency on hard materials is increased by additions up to 3.0 per cent. By increasing the silicon above 3.0 per cent., however, the cutting efficiency begins to decline. Various experiments were made with other metals as alloys, but the results obtained were not sufficiently good by comparison with the above to call for comment. Analysis of one of the best qualities of rapid steels produced by Mr. Gledhill's firm (Armstrong Whitworth Co.), is as follows: "A. W." steel Carbon 0.55 per cent; Chromium, 3.5 per cent.; Tungsten, 13.5 per cent. Tools made from high speed steels in order to give best results when heavy cuts and coarse feeds are employed, should be made of a form that insures strength and rigidity and must cut freely. Many times tools are made having very little clearance on the portion that penetrates the stock as shown at A Fig. 161; now if a coarse feed is employed it is apparent that such a tool will bear on the stock below the cutting edge, as a consequence the tool cannot cut as rapidly as the lathe carriage is traveling and it must turn in the tool post. If the operator is not attentive he will not observe the trouble, and in order to securely fasten the tool he will tighten the binding screw so tightly that he either breaks the tool post binding screw or he succeeds in binding the tool so it cannot turn, and the feed belt slips, or the pressure against the stock actu |