708 TRANSACTIONS OP SECTION G. 



The following Paper was then read : — 



The Testing of Lathe Tool Steels. 1 

 By Professor W. Kipper, D.Eng., M.Inst.C.E. 



A great deal of testing of lathe cutting tools has been done in the past by 

 various experimenters, and is being done every day by steel manufacturers for 

 their own information, but there is, unfortunately, an entire absence of uniformity 

 of standard in the making of these tests. There are two methods of testing- 

 most commonly adopted. The first is to find the length of time the tool will 

 run in the lathe under a given set of constant conditions before requiring 

 regrinding; the second is to find the cutting speed which shall cause the edge 

 of the tool to be completely ruined in twenty minutes. 



Tests representing prolonged durability are of doubtful value. It is more to 

 the purpose to know the highest cutting speed which may be maintained during 

 some practical period of time— say, twenty or thirty minutes— without re- 

 grinding. 



Mr. Taylor recommends that in the case of the twenty minutes' test about 

 eight tools of each kind should be prepared— say, 1£ by If and about 18 inches 

 long — treated and shaped in every way alike. They should then be run one tool 

 after another each for a period of twenty minutes, and each at a little faster 

 cutting speed than its predecessor, until the cutting speed has been found which 

 will cause the edge of the tool to be completely ruined at the end of the twenty 

 minutes. This speed is then called the ' standard speed.' 



As an improvement on each of the previous methods of testing the writer 

 submitted a new method, which he calls the ' speed-increment test,' and which he 

 has found to give reliable results with a minimum expenditure of time and 

 material. 



The method is as follows : — 



A testing lathe sufficiently large for the purpose, and driven electrically, is so 

 fitted as to be capable of a very fine adjustment of speed of rotation. The tool 

 to be tested is started on a standard cut — say, \ by \ — in the testing lathe at a 

 surface speed of, say, 30 feet per minute, and the cutting is allowed to proceed 

 under a gradually increasing rate of speed by equal increments of one foot per 

 minute, each minute throughout the test, until the tool breaks down. That is to 

 say, the speed increment is increased gradually and regularly while the test is 

 proceeding, in the same way as the load increment is increased in the tensile test 

 of a steel bar in the testing machine. Then, if the mean cutting speed in inches 

 from start to finish of the trial be multiplied by the duration of the trial in 

 minutes and by the area of the cut, the result is equal to the number of cubic 

 inches of material turned off by the tool during the test, and this is the measure 

 adopted to represent the merit of the tool. 



FRIDAY, SEPTEMBER 2. 



The following Report and Paper were read : — 



1. Third Report on Gaseous Explosions. — See Reports, p. 199. 



[2. The Testing of Files. 3 By Professor W. Ripper, D.Eng., M.Inst.C.E. 



The writer is not aware of the existence, until recently, of any method of 

 testing the cutting power of files, except by handing the files to skilled workmen 

 and obtaining their reports upon them. This method is obviously open to grave 

 objections, but a few years ago the Herbert file-testing machine was introduced, 



1 Published in Engineering, September 9, 1910. 



2 Published in the Proceedings of the Sheffield Society of Engineers and 

 Metallurgists, November 1910. 



