The Impact of Built-Up Edge on Parametric Failures of Machine Reamers when Machining Structural Steel

This paper describes the relationship between wear and build-up formation when machining holes in structural steel by machine reamers. The author presents the results of studying the height and position of the build-up on cutting and calibrating edges when modelling the operation of one tooth of the tool with average values of the above-mentioned indicators when machining by reaming. It is established that an increase in wear, both when modelling the tool operation and with real reaming, is accompanied by an increase in the build-up height and its movement from the main cutting edge to the auxiliary calibrating edge. At a certain wear value, the build-up bulges out beyond the forming calibrating part of the tool, which compromises the accuracy of machining. When the wear exceeds the width of the calibrating strip, the reaming process undergoes qualitative changes. This results from the fact that the probability of the build-up detaching from the calibrating strip is very high, and the build-up stability decreases. Reaming becomes less stable, accuracy and smoothness indicators change and become more dispersed. The instability of the build-up has a significant impact on the wear of the calibrating strip, and scratch marks and stripes appear overtime. A statistical analysis of the mean square deviations of reaming distribution and roughness, obtained within the wear limits of the reamer, up to the width of the calibrating strips and exceeding this value, has shown significant variations at the probability P = 0.95, which confirms the qualitative change in the wear process.

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