Deburring and Texturing Bone Screws

The job: Manufacture titanium bone screws with tight tolerances.

The challenges:

Titanium is an excellent material for bone screws, but it hardens as it heats up, making it tough to machine, leaving fine feather burrs. These burrs must be removed without damaging or dulling the cutting edges on the screw. In the case of self-tapping screws, gentle removal is especially critical because it is easy to ruin the integrity of the flute.
The screw head may also require a textured finish that ends precisely before the threads.

Deburring and texturing bone screws with Comco’s Advanced Lathe.

Deburring the Threads

Two abrasives work best for this application: sodium bicarbonate and glass bead. Sodium bicarbonate gently removes burrs on a bone screw without dulling the cutting edges. Glass bead both removes fine feather burrs and creates a compressive layer on the surface of the threads. This layer helps to improve the fatigue life on the bone screw. Caution: Over-blasting—or blasting too forcefully for too long or with too much abrasive—rounds or dull most part edges. Therefore, it is essential to acutely monitor blast time and coverage when using glass bead.

Recommended Approach

Nozzle: 0.046” or 0.060” Hi/Performance
Pressure: 60-100 psi
Abrasive: 50 µ Sodium Bicarbonate or Glass Bead
Orifice: 0.030″

Texturing the Head

Some bone screws require a second blasting application: texturing. Texturing the surface on the head of the screw improves the mechanical bond with a swivel or another fixation device. MicroBlasting provides the precision to selectively texture this portion of the screw and using aluminum oxide to texture creates more surface area and greater points of contact between the screw and the device.