TOOL STEEL FOR THE UNITED STATES NAVY. 353 



in brine, after which the temper was drawn in a lead bath. The cutting 

 tools were then ground and were ready for the selective test. 



The proportions of the milling cutter used for the selective tests for 

 carbon tool steel, classes i and 2, shown on sheets Nos. 1058 and 1521, Plates 

 142 and 144, were adapted from an article by Mr. A. L. Deleeuw, in the 

 Transactions of the American Society of Mechanical Engineers. The prin- 

 cipal difference from milling cutters in general use is in the comparatively 

 small number of teeth permitting a larger clearance for the chips. This 

 cutter is so small that it was necessary to support the outer end to enable 

 it to stand the heavy cut desired to give a break-down test similar in purpose 

 to that developed for tungsten tool steel, class i . The cutter was operated 

 at the speed of 370 revolutions per minute, feed 20 inches per minute, and 

 0.08 of an inch depth of cut through the full table travel of the milling 

 machine. The table was run back to the starting point and reset as often 

 as necessary until the cutter failed. The cutter was run without lubricant 

 in order to make the test as severe as possible and there was a generation of 

 heat similar to that developed by the tungsten tool steel, class i, test, and 

 blue chips were occasionally produced. The cutters made of carbon tool 

 steel would become so hot that they would twist ofif in the cutting part of 

 the tool, but the cutters made of tool steel containing tungsten, although 

 operating at equal temperatures, would twist off in the shank. The former 

 phenomenon is due to the drawing of the temper of the carbon tool steels, 

 but the introduction of tungsten apparently prevents this action, enabling 

 the tools to withstand heat break-down. The cutting edge of the tools 

 containing tungsten would dull gradually, thereby increasing the tortional 

 stress which ultimately equalled the physical strength of the material. The 

 effect of tungsten is also shown in the greatly lengthened elapsed time of run 

 or cutting life of the tools. The cutters are shown on Plate 138. 



The heat treatment for these tool steels containing tungsten is not 

 different from that of carbon tool steels ; so that their introduction to the 

 navy yards will cause no change in the present methods of treating tool 

 steels, and there will be the added advantage of a much superior cutting 

 tool steel. 



The cape chisel used for the class 3 carbon tool steel selective test is 

 shown on sheets Nos. 1058 and 1521, Plates 142 and 144. In some of the 

 early tests and in the yard generally trouble was experienced by the occa- 

 sional breaking of the shank of the hammer end of the chisel. But this 

 trouble has been overcome so far as the selective tests are concerned, and 

 reduced so far as the yard is concerned by treating about half an inch of the 

 hammer end of the body with the shank and quenching by dipping about 



