350 TOOL STEEL FOR THE UNITED STATES NAVY. 



The selective test tool for class 3 carbon tool steel was a pneumatic 

 cape chisel, shown on sheet No. 1058. The chisels were operated until they 

 failed either by the breaking of the cutting edge, dullness or wearing of the 

 sides, so that the length of the cutting edge was reduced. The chisels were 

 reground and given a second test, and the total distance cut was recorded. 

 The selective factor represents the ratio of the mean distance cut by the 

 chisels of one sample to the price per pound of that sample. 



A button-head rivet set was used as the selective test tool for carbon tool 

 steel, class 4, and is shown on sheet No. 1058, Plate 142. The sets were 

 tested by driving a certain number of hot rivets, and their condition after 

 the test was observed and a record made of the comparative conditions. No 

 selective factor was computed because the test is not so decisive as the pre- 

 ceding tests, but this class of tool steel is, of course, not intended for cutting 

 tools. 



The data of the selective tests, the chemical compositions, and the rela- 

 tive values computed for the above classes of carbon tool steel are given on 

 sheet No. 1058, Plate 142. 



Schedule 446Q. — ^After the selective test of Schedule 3893, it was con- 

 sidered advisable to revise the specifications for reasons similar to those 

 previously given. The new specifications are given in Appendix D. 



The conditions throughout the selective test were maintained as nearly 

 uniform as facilities would permit, and the operating life of the tools deter- 

 mined as previously described. Before the tools were treated a determina- 

 tion was made of the decalescent point of each sample to assist in selecting 

 suitable treating temperatures. The heating and cooling curves of the 

 samples are given on sheet No. 152 1, Plate 144. 



Some of the bidders took advantage of the clause in the specifications 

 which permitted tool steels to be submitted of a chemical composition dif- 

 fering from that specified. Tool steels containing tungsten were submitted 

 under carbon tool steels, classes i and 2, and a tool steel containing chromium 

 was submitted under carbon tool steel, class 3. 



The selective test tools used are shown on sheet No. 1521, Plate 144, 

 and it will be noted that the milling cutter is the only one changed from the 

 selective test tools shown on sheet No. 1058, Plate 142. The change in the 

 mining cutter was made in order to support the outer end so that it could 

 better withstand the strain of the test. The method of conducting the 

 selective test was similar to that described for the preceding schedule. It 

 was at first intended to adjust the observations of this test by the principles 

 of least squares, but the variations of the observations were such that it was 

 decided the results thus obtained would not warrant the labor involved. 



