A sliding headstock lathe feeds raw stock via axial movement of the main spindle, paired with stationary cutting tools for material removal. Compared with conventional lathes, its key merit lies in continuous support of the workpiece close to the guide bushing throughout machining, eliminating deflection caused by long overhangs.

Taking the Citizen L12-1M7 as an example, it delivers a positioning accuracy of ±0.005 mm and repeat positioning accuracy of ±0.002 mm-roughly one-twentieth the diameter of a human hair. This ultra-high precision is indispensable for slender tubular VABB needle components, which feature outer diameters of only 2–4 mm and lengths up to 150 mm.

The needle tip is the most complex component of the VABB needle, requiring three curved surfaces machined to form razor-sharp cutting edges. The machining workflow proceeds as follows:

First, SS316 stainless steel tubing is loaded into the spindle. A 0.4531-inch flat end mill machines the first bevel perpendicular to the cutting feed path. The workpiece is then rotated sequentially to machine the second and third bevels. The angle of every bevel is held to a tolerance of ±0.1°, with zero burrs permitted at intersecting edges.

The full milling cycle lasts approximately 30 minutes, with continuous coolant flushing to mitigate thermal deformation. Post-machining, a profile projector verifies cutting edge geometry for full conformance to engineering drawings.

A lateral sample notch is milled into the cannula wall to hold tissue drawn in by vacuum suction. The auxiliary milling spindle of the sliding headstock lathe performs notch cutting, with slot width and depth tolerances controlled at ±0.01 mm.

A laser marking system subsequently etches depth scales or identification codes onto the cannula exterior, enabling physicians to gauge puncture depth under ultrasound or X-ray guidance. Laser marking is a non-contact process that introduces no residual mechanical stress or surface contamination.

The cutting cannula severs tissue after vacuum aspiration. Its front end undergoes flaring to create a hermetic fit with the needle tip, while an internal chamfer is machined on the rear end for secure vacuum line connection.

All forming operations are completed in a single clamping setup on Citizen lathes, erasing alignment errors from secondary re-fixturing. Finished cannulas undergo go/no-go gauge inspection of inner and outer diameters to guarantee coaxial alignment with the needle tip and sample notch cannula.