The development of a testing machine for machinability tests

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Virginia Polytechnic Institute


It is a well established fact that all materials have a difference in chemical composition and show different physical properties. Long experience with the machining of materials had shown this investigator that in many respects the machining of each material differed slightly from the machining of any other material. This led to the idea that perhaps the one factor which had been overlooked by other investigators in the field of machinability was the factor of time. The question was, “Could a machine be built which was capable of measuring the differences in materials in terms of the variation in the times required to remove metal under a given set of conditions?”

The first step in the program to answer this question was to build a machine which would be rugged enough to make heavy cuts possible, and still be sensitive enough to measure what might turn out to be very small variations in time. This machine has now been built. While it still has a long way to go to become perfected the results are encouraging enough to create the desire to continue with the work along this line.

The second step in the program was to design tests which would not only serve to test the functioning of the machine, but would serve to indicate along what lines the future work should follow. The one hundred and twenty-five tests made have proved two facts quite conclusively. The first fact is that the idea on which the testing machine was designed is fundamentally sound. Time variations can be used to measure machining characteristics of different materials. The second fact proved by these tests is that the machine is not only capable of measuring the differences existing between various materials, but that it can be used to test such factors as the proper tool angles to use in machining a given material, the force required to remove a given volume in a given time, and the best speeds to use to give the smallest time per unit volume.

It was evident during these tests that several minor changes could be made to improve the performance to the point where it would be even more capable of showing the time variations which occur. These changes have been incorporated in the following section of the thesis.