Tips for Sanding Titanium Parts Safely and Efficiently

Quick take: Titanium finishing can become a major cost driver because sanding has to remove burrs and improve finish without overheating or damaging the part. This page is strongest when it is read with burr-control and material-behavior references that reduce finishing work upstream.

Related references: Chamfers and Countersinks That Halt Burr Formation, Effectively Reaming Nickel-Base Alloys, and Understanding Hardness in Metalworking.

Sanding, or benching, titanium alloy parts is a major cost element of the manufacturing process. Sanding removes burrs and improves surface finish to achieve drawing specifications. Sanding is also done to blend steps between cutter passes and remove material that milling missed. There are some difficult areas to access when milling and it is sometimes more efficient to sand and blend at the bench than to spend extra time milling certain features. Benching can cost less per hour because those employees are usually paid less than machine operators and because expensive capital equipment is not being tied up.

Minimizing sanding offers the potential for large savings because it typically adds 10 to 20 percent to the cost of titanium alloys parts. The key reasons for the high cost of sanding are material hardness, demanding specifications and inefficient milling operations.

Deburring titanium alloys via sanding takes a lot of effort. The titanium alloys are often quite hard (41 HRC), which makes sanding difficult.

Titanium alloys lose some desired properties if they get too hot during sanding. If the surface gets above 800° F, small cracks form and fatigue life is reduced. Therefore, aggressive sanding, especially when generating white sparks, is not allowed. The workpiece surface often turns blue when the temperature goes above 800° F. To avoid that, sanding must be done at slow speeds to maintain material integrity.

At Boeing, a contributor to the high cost of sanding is the company’s deburring/sanding specification. This specification requires a 32μin. Ra finish on titanium alloys if sanded, even if the drawing requirement is 125μin. Ra for the surface in question. This requirement does not usually apply when sanding other metals.

Sanding creates scratches, or points, in the workpiece surface. In contrast, milling generates points that project up from the surface. The machined “up” points pose less of a fatigue problem than the sanded “down” scratches. Fatigue tests performed during development of the Super Sonic Transport led to the 32μin. Ra surface finish requirement if sanding is performed. Further testing in 2003 confirmed that bad fatigue test results were generated from sanding titanium alloys.