MECHANICAL FACTORS AFFECT LUBRICATION IN METAL CUTTING

It has been found that mechanical factors need to be considered along with chemical and physical characteristics of the fluid when specifying the proper lubricant for certain machining operations. These factors include roughness and relief angles of the cutting tools and modulus of elasticity of the work material. In interrupted cuts such as milling and gear cutting the tools can be too smooth to achieve maximum lubrication. In other operations such as tapping, broaching, or reaming, an effective lubricant may actually increase power requirements because of small relief angles. A cutting fluid that works well for steel materials, may be found to be poor for aluminum not because of chemical properties, but because of the lower stiffness of aluminum. The paper gives experimental evidence of these characteristics and discusses the fundamental reasons for their occurrence.