This section is from the book "Lathe Design, Construction And Operation, With Practical Examples Of The Lathe Work", by Oscar E. Perrigo. Also available from Amazon: Lathe Design: Construction And Operation.
In reference to the use of high-speed steel in a very large and general way, for all classes of work upon which it is possible to use it, there seems to be no doubt. It has been proven many times, in many places, under many conditions and on almost every conceivable material that has to be handled in machine tools, that it has "come to stay" and that any information regarding it is of practical use.
The following remarks, giving the experience of one practical and observing machinist whose name, unfortunately, is not at hand so that proper credit can be given him, are here introduced as being valuable in this connection, and practical from the machine shop point of view:
"The first thing is to make up one's mind as to the quality or kind of steel to use, which means to be satisfied with the steel which has been found to work best in one's own shop. This has been a difficult matter for superintendents and foremen to decide, because it is so hard to discover the best way to determine which steel will do the most work, and experience has taught most of us that any of our high-speed steels, when properly treated, will do considerably more work than the machine is capable of.
"I do not think it advisable to have too many different kinds of stock in the works; results depend entirely upon the way of forging and treating the tool. If the tool-maker is familiar with one or two grades of the best high-speed steel, and the quality is found satisfactory, and bringing about the best results that the machines can stand up to, these are the steels that should be adopted.
"Each of these steels must be treated differently, and if the tool-maker succeeds in treating one grade properly and understanding it thoroughly, it means much time saved and better results in the shop.
"In introducing the use of high-speed steel in a shop, like everything else that is to be a success, one must start right. That is, the work should be undertaken by some responsible person - superintendent, foreman or speed boss, in other words, the man who is responsible for the work turned out in the machine shop. All tools, of course, have some particular way of treating, which should be understood by the person in charge. Now it is 'up to the forger.'
"The person in charge should see that the tool has its proper treatment, as success in most cases lies with the treatment. When the tool is finished, and the superintendent or foreman is satisfied that it has been properly treated in accordance with directions, it is ready for grinding and for making a test. It should be ground on a wet emery wheel, and care taken to heat the tool just so it can be touched with the fingers.
"The tool once ground and ready to do the work, the question often arises, 'What lathe, planer, or machine are we going to put it into?' In most cases when a new tool is tried, it is put in a lathe, to do turning; so naturally the superintendent or foreman would pick out the best lathe that was in the shop, i. e., the lathe that was considered to have the most power.
"Being now ready to make the test, it is generally tried on steel; that is considered by most superintendents and foremen the severest test to make. Take a piece of steel of almost any diameter, and of the quality most used in the shop, and prepare to take the cut. It seems to puzzle most every foreman to know just what to do and where to start. I speak now of what I have seen, and of the men who are sometimes sent by the steel makers to demonstrate the use of their steels.
"I think the proper way is to get at least one dozen shafts of a standard size that are used in the regular line of product, and to first look up the exact time it took to finish or rough off the previous lot; then to determine about what percentage of time would be considered a fair gain to warrant adopting the steel, based on the price per pound of the steel being used. Let it be based at 25 per cent, which I find in most shops can be accomplished, and the lathe be speeded up faster than when the last lot was turned, starting with the same feed and about the same cut, which most any lathe will stand. The superintendent finds, after he has roughed off about two or three pieces, that the tool seems to stand up all right.
"The next step is to find out about the speeds and feeds. The first thing is to increase the feed with the same speed the machine is running at. In most cases which I have seen, after the tool has traveled a certain distance the cutting edge would break or crumble, and the foreman would say, 'Just as I expected. All this highspeed steel will do the same thing!' forgetting he had just been doing over 25 per cent more work than ever before, without the least bit of trouble.
"Now the tool is taken out and looked over, and it is found that a portion of its cutting edge has been broken off. Here is where most foremen make a mistake; they take the tool back to the forger or tool dresser to have it re-dressed and treated over. If it is only broken off slightly and can be ground, even if it take ten or fifteen minutes to grind, it should be done by all means. My experience has taught me it will prove a better tool than before, but care must be taken not to overheat in grinding.
"The tool is now put back in the lathe, which is started again; and generally, to one's astonishment, it will be found that the tool will stand up all right. One should not be too anxious to break the tool again (!), but should turn up two or three more pieces with an increase of feed, keeping a record of the time it takes to turn up each piece.
"Once convinced that the tool will stay up all right with the increase of feed, the foreman can increase the speed one step on the cone. About the time this is done, it is found either that the belt slips, the lathe is stalled, or the countershaft will not drive. (It is my opinion that in most all machines which have been built up to a year or so ago the countershafts are not strong enough in comparison with the machine tools.) Now, no doubt if these things had not occurred the tool would have done better; but in this case, reduce the speed, and finish the twelve shafts, which it will probably be found can be done without grinding the tool.