Now let us take our test piece to the grind stone and grind it down to the shape of a cutting tool. It is necessary to resort to the grind stone, in order to get the desired shape, because of course, our test piece is far too hard to cut with any other metal. After having produced a tool of the desired shape and size, let us fasten the same securely into the carriage of a lathe, and then upon applying the cutting edge to a revolving piece of cast iron, or soft steel, or even to a piece of the very same grade of steel out of which the tool was made, only while it is still in the softened or annealed condition, we find that it is capable of easily and quickly cutting out a good sized ribbon of chips from the metal which is to be machined. However, we are soon confronted with a new difficulty, for as the cut progresses, our tool runs into a rough spot which causes it to tremble and chatter and then suddenly our tool cracks in two in the middle and is at once completely ruined. It is evident that as we are able to increase the desirable element of hardness in a piece of tool steel, we also automatically increase the undesirable element of brittleness, and therefore some new method must be devised which will allow a sufficient degree of hardness to allow the tool to cut other metals and at the same time not cause so much brittleness that it will crack in two at the first rough spot which it encounters. One method of assisting the toughening of a piece of hardened tool steel is accomplished by the process of “drawing”. This simply means heating the piece of hardened tool steel up to some fairly warm temperature, which of course must be kept well below the critical range (at which the steel would jump at the chance to quickly change back into one of its softer allotropic forms) and then keeping the steel at this drawing temperature for a while until the unusual strains and stress caused by the rapid cooling have had an opportunity to have become somewhat relieved. Therefore, the process of “drawing” is quite as important as is the first act of hardening itself, and great care must be exercised in undertaking the same. CHAPTER IV. HIGH SPEED STEELS.