The only true test for a brand of high-speed steel is the service that it gives by continued performance month in and month out under actual shop conditions. The average buyer is not justified in conducting a test, but can well continue to purchase his requirements from a reputable manufacturer of a brand that is nationally known. The manufacturer is always willing to cooperate with the trade in the conducting of a test and is much interested in the information received from a well conducted test. A test, to be valuable, should be conducted in a manner as nearly approaching actual working conditions in the plant in which the test is made as is practical. In conducting a test a few reputable brands should be allowed to enter. All tools entered should be of exactly the same size and shape. There is much difference of opinion as to the best practical method of conducting a test, and the decision as to how the test should be conducted should be left to the customer, who should cooperate with the manufacturers in devising a test which would give the best basis for conclusions as to how the particular brands would perform under actual shop conditions. The value of the file test depends upon the quality of the file and the intelligence and experience of the person using it. The file test is not reliable, but in the hands of an experienced operator, gives some valuable information. Almost every steel treater knows of numerous instances where a lathe tool which could be touched with a file has shown wonderful results as to cutting efficiency. Modern tool-steel practice has changed from that of the past, not by the use of labor-saving machinery, but by the use of scientific devices which aid and guide the skilled craftsman in producing a steel of higher quality and greater uniformity. It is upon the intelligence, experience, and skill of the individual that quality of tool steel depends. HARDENING HIGH-SPEED STEELS We will now take up the matter of hardening high-speed steels. The most ordinary tools used are for lathes and planers. The forging should be done at carbon-steel heat. Rough-grind while still hot and preheat to about carbon-steel hardening heat, then heat quickly in high-speed furnace to white heat, and quench in oil. If a very hard substance is to be cut, the point of tool may be quenched in kerosene or water and when nearly black, finish cooling in oil. Tempering must be done to suit the material to be cut. For cutting cast iron, brass castings, or hard steel, tempering should be done merely to take strains out of steel.