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Bone loss due to thermo necrosis may weaken the purchase of surgically placed screws and pins, causing them to loosen postoperatively. The heat generated during the bone drilling is proportional to cutting speed and force and may be partially dissipated by the blood and tissue fluids, and somehow carried away by the chips formed. Increasing cutting speed will reduce cutting force and machining time. Therefore, it is of interest to study the effects of the increasing cutting speed on bone drilling characteristics. In this article, the effects of the increasing cutting speed ranging from 500 up to 18,000 r/min on the thrust force and the temperature rise are studied for bovine femur bone. The results of this study reveal that the high-speed drilling of 6000-7000 r/min may effectively reduce the two parameters of maximum cortical temperature and duration of exposure at temperatures above the allowable levels, which in turn reduce the probability of thermal necrosis in the drill site. This is due to the reduction of the cutting force and the increase in the chip disposal speed. However, more increases in the drill bit rotational speed result in an increase in the amount of temperature elevation, not because of sensible change in drilling force but a considerable increase in friction among the chips, drill bit and the hole walls.

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In case of human bone fracture, the best way to better and faster knitting is when a traumatologist fixes the fractured bone ends by drilling and setting the immobilization plates by screws. Heat generation during bone drilling may result in thermal injury due to exposure to elevated temperatures, with potentially devastating effect on the outcome of orthopedic surgery. A recent and promising method for reducing temperature in bone drilling is the use of ultrasonic assistance, where high-frequency and low-amplitude vibrations are added in feed direction during cutting process. In this research, experimental tests are carried out in five cutting speeds and three feed rates. The results demonstrate that ultrasonic-assisted drilling offered lower thrust forces and lower process temperatures as compared to conventional drilling at 1000 r/min. In addition, it is obvious that at 2000 r/min, since the values of temperature rise and thermal injury are independent from the feed rate, this method can be applied in the orthopedic surgery.

In dry grinding, as there is no coolant lubricant to transfer the heat from the contact zone, generation of surface damages are not preventable. Promising alternatives to conventional flood coolant applications are also Minimum Quantity Lubricant (MQL) or Near Dry Machining (NDM) or Semi Dry Machining (SDM). As the name implies, MQL machining uses a very small quantity of lubricant delivered precisely to the cutting zone. Often the quantity used is so small that no lubricant is recovered from the parts. Any remaining lubricant may form a film that protects the parts from oxidation or the lubricant may vaporize completely due to high temperatures of the cutting zone. A number of studies have shown that MQL grinding can show satisfactory performance in practical grinding processes. However, there has been little investigation of cutting fluids to be used in MQL grinding. In this study, several grinding fluids, including mineral, vegetable and synthetic esters oil, are compared on the basis of the grinding forces and surface quality properties that would be suitable for MQL grinding applications, to develop a multifunctional fluid having the MQL results such as cooling, lubrication and high ecological and environmental safety performances. The grinding performance of fluids is also evaluated in dry and conventional fluid grinding techniques.

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