Abstract
The authors present a considerable amount of data on the life of tools under shop conditions machining free-cutting brass in automatic screw-machines. The analysis of this data shows that larger feeds and higher cutting speeds than those used in current practice can be combined with a reasonable tool life. The type of relation existing between cutting speed, feed, and life of tool found by Frederick W. Taylor and others for rough-turning of steel does not fit these tests of forming and drilling free-cutting brass. Within the limits of these tests an increase of the cutting speed is accompanied by greater economy. When machining free-cutting brass with ground circular-form tools, the life of the cutting tool between grinds appears to be nearly independent of the feed and of the cutting speed, and to depend primarily on the linear distance the work moves in contact with the tool. This indicates that the wear is primarily a lapping action, which is influenced more by the amount of movement of the edge of the tool against the work than by the pressure between them. Within the limits of the tests the maximum economy in machining free-cutting brass is secured by using the largest feed that the work and tools will stand and by running the stock at the highest spindle speed available.
