As a result, more manufacturing engineers are learning that machining these alloys can be a tricky job due to their unique physical and chemical properties. The problems that arise in drilling, turning, and grinding of titanium can be better understood if we look at these properties. They hold the key to successful machining operations. Table 1 compares the general properties of commercially pure titanium with other commonly machined metals. In tensile and sheet stiffness, titanium falls between steel and aluminum.
Thermal properties are another matter.
Titanium alloys have high melting points, which is usually a sign of excellent temperature stability. However the strengths of titanium alloys fall off rapidly at temperatures above 800 F, and their coefficients of expansion are even less than that for steels. These unusually poor thermal properties account, to a large extent, for the difficulties in machining titanium. These allotropic forms of titanium are known as alpha and beta respectively. Alloying elements favor one or the other.