Titanium (symbol Ti) is a light, hard, lustrous silvery-white metal with an atomic number of 22 and an atomic weight of 47.88. It is part of the transition metal group. Discovered in 1791, the pure metal wasn't isolated until 1910. It has a high melting point of 1,668 degrees Celsius, but can be forged at temperatures near its melting point. As fine shavings or a powder, titanium in the air can be easily ignited and will burn very hot. Titanium resists corrosion from fresh or salt water, but will dissolve in concentrated acids. It's a hard metal, measuring a 6 on the Mohs scale (where diamond is a 10).
Titanium has a reputation for being difficult to machine. That reputation comes from the basic characteristics of titanium metal. Because titanium is a poor heat conductor, the heat generated by cutting and grinding actions doesn't dissipate quickly, so most of the heat stays concentrated on cutting tool edges or the face of grinding tools. Titanium becomes chemically reactive at the high temperatures generated by machining and can react with the machine tools, causing spot welding, galling and smearing that quickly ruin machine tools and the workpiece.
Titanium has more springiness than steel, meaning it tends to deflect away from a machine tool unless the workpiece is rigidly supported. Titanium doesn't build up a heat-absorbing "edge" ahead of a cutting tool, resulting in super-hot spots along the edge of the tool. This creates tiny craters close to the cutting edge, causing rapid tool breakdown. Also, inadequate attention to heat buildup during machining can result in metal weakness due to micro-cracking, heat deformation and residual tensile stresses.
Many machinability problems with titanium can be avoided by using proper techniques that keep temperatures down. Use a low cutting speed, set at about one-eighth the speed used for steel, to reduce tool temperature by more than 50 percent. Maintain a high-feed rate for your machine tools, consistent with good machining practices. Never stop feeding the tool while it is in contact with the moving workpiece. Allowing a tool to be in moving contact without feeding can spoil the workpiece surface and ruin the tool. Rigidly support the workpiece. Use lots of cutting fluid to lubricate edges, carry away heat and wash away chips. Use sharp tools and replace them at the first signs of wear.