As the name implies, the padded reamer differs from a fluted reamer in that the padded reamer has a cutting surface and guide pads that ride on the diameter of the hole to put pressure on the cutting surface which generates the hole size and geometry. The guide pads also act as a burnishing tool to help provide a smooth surface finish. Since the pad forces are “riding” on the inside surface of the hole, significant lubrication is necessary in padded reamer operations to eliminate scratches on the hole surface and maintain the required surface finish.
High pressure die casting is a process of forcing molten alloy at high pressure into a die. Common alloys are alumi¬num, zinc and magnesium. The dies can be very complex and the variation of parts produced is extensive. Due to the wide variation in die design, size and complexity, the flow of alloy through the die and the thermodynamic profile of each system is unique. This leads to tempera¬ture variation, hot areas and cold areas on the die sur¬face. Two of the major roles of a die casting lubricant are, protect the die from the molten alloy and provide release of the casting. Therefore the need for a lubricant to be effective in a broad temperature range is preferred.
A key contributor to shortened die life is thermal fatigue. In high pressure die casting, production cycle times typically range from a few seconds to just over a minute. Within this span, the die cavity is being sprayed with die lubricant (the lubricant may be cold, cool, or hot, depending on the environment), then the die is sprayed with compressed air, closed, and finally injected with very hot molten alloy. Throughout this production cycle, the temperature of the die steel sharply rises and falls. As a die is continually cycled, the yield strength of the tool steel is reduced, which causes tensile stresses that lead to cracking of the tool.