Cocquilhat’s first documented (1851) how heat in a tool shortens the life of the tool. Research since his time has generally concluded that the tool gives up a relatively higher percentage of it’s “cold hardness and toughness” as compared to the work stock. This paper looks at the previously unstudied advantages/disadvantages which may be gained by pre-heating the work stock to a relatively modest temperature, thereby preferentially shifting the ratio/percentages back toward the tool. A widely-used body centered cubic (BCC) steel and a widely-used face centered cubic (FCC) aluminum were chosen to test common commercially machined crystalline structures. The materials were heat treated and/or aged to provide various levels of hardness within the crystalline structures. The selection of two cutting speeds, two levels of cut and three tool rake angles completed the factor level combinations chosen for the study. Parts were preheated immediately prior to the machining operations with an additional resistance heater mounted in the work holder to maintain the temperatures during the trial run. Tensile specimens of all the samples were undertaken to establish the cold working flow stress values of the materials tested. Machining was conducted in a specially modified Cincinnati Horizontal Milling machine using an improved Videographic Quick Stop Device (VQSD) to capture the geometry of the cutting formation simultaneously with the forces in the X, Y and Z-axes using a standard Kistler force plate dynamometer. Utilizing the VQSD greatly increases the number of replicates available for statistical analysis by the metal cutting researcher. This allows for comprehensive multivariate analysis of the data with high confidence (> 95%) in the obtained results. Forces and geometry were collected and analyzed. Wear was measured on the face of each tool using surface profilometers and white light microscopy. The specific horsepower (HPs), also known as the specific cutting energy, normal force (N), and wear rate data indicated there is a definite advantage to be had in pre-heating the workpiece by even a modest amount. In fact, the temperature was a significant prime factor (p-value <= 0.0001, Fstat > 5 with 95% certainty) in all factor level combinations. It was often ranked as the primary number one factor or the number two ranked factor. Many interactions with the temperature were also significant. This, combined with improved tool cooling methods, should result in all tools living a longer time while undergoing less chatter and/or deflection.

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