Reactivity of Titanium with Abrasive Materials and Its Polishing.

Titanium is a difficult-to-machine metal, due to its high reactivity with abrasives. The cutting rate of alumina is significantly low. In contrast, at higher rotational speed and greater grinding force, the cutting rate of carborundum is much greater, but accompanied by severe loss of the tool. Since titanium has low thermal conductivity, the grinding temperature influencing titanium-abrasive reactions should be kept from rising. Relatively low rotational speed and small force are recommended. In addition, the tool should not be depressed against the work during grinding but moved over the work, otherwise unfavorable results are yielded: abrasive attrition, chip loading and oxidation of the surface, or grinding burn. Since polishing is also a procedure of cutting by abrasives, inhibition of titanium-abrasive reaction is an important key to efficient polishing. Recently, two finishing techniques were successfully applied in dentistry, electrochemical buffing and mechanical buffing with colloidal silica as abrasive. When the reaction-inhibition mechanism is clarified in these techniques, a new development will be possible.