Swiss-turned stainless shaft at production volume

The shaft runs in 303 and 316 stainless depending on the assembly, purchased to bar-stock tolerances that suit Swiss-type guide-bushing work and supplied with mill certifications recorded against the lot. 303 machines freely and suits the higher-volume releases; 316 is specified where corrosion performance governs, at the cost of a stickier chip and a shorter tool life per edge.

Both alloys were qualified on the same program with their own speed, feed and tool-life parameters, so a change in material does not become a change in process. Surface finish is the specification that drives the cut: the bearing diameter is produced with a finishing insert at a feed selected for finish rather than for cycle time, and the finish is verified rather than assumed.

Burr condition and edge break are called out on the print and treated as inspected characteristics, not as cleanup. A cross-drilled hole intersecting a finished diameter is exactly where an unaddressed burr causes an assembly problem downstream.

The part is produced complete on Citizen Swiss-type lathes — an L20 for the larger diameters and an L12 for the smaller — running from bar with a sliding headstock and a guide bushing. Because the bushing supports the material a few millimetres from the cutting edge, the shaft is never machined unsupported, which is what makes a ground-quality finish achievable as-machined instead of as a second operation.

Live tooling produces the cross-drilled feature in cut, and the sub-spindle takes the part for backworking so it comes off the machine finished, cut off and deburred. Bar feeders allow the cell to run unattended into the night, and part counts, tool-life limits and in-cycle checks are set so an unattended run ends in a bin of good parts rather than a surprise.

This is the standard approach described on our Swiss turning page: small, slender, high-volume parts finished in one pass through the machine. Consolidating turning, cross-drilling, backworking and deburring into a single cycle removed the grinding vendor, one queue and one set of handling risks from the routing. The documentation expectations behind it are described on our medical device machining page.

Dimensional verification runs on a Keyence IM image dimension system, which measures the full profile of the part optically in seconds rather than one characteristic at a time with a hand instrument. First, middle and last parts of every run are measured, and the system produces the report automatically, so the record is generated by the measurement rather than transcribed after it.

At the machine, certified pin and bore gaging covers the diameters between optical checks, and the operator records readings on the setup sheet at defined intervals. Finish is verified against the print requirement, and the cross-drilled feature is checked for burr condition on every sampled part.

Each lot ships with its inspection report, material certification and certificate of conformance, filed against the released print revision. Because the report is machine-generated and attached to the lot, an audit of a shipment from six months ago is a records lookup rather than an investigation.

The finish requirement is met as-machined. The grinding operation is gone, and with it a vendor, a shipping leg, a queue and a second opportunity to damage a finished diameter in handling. Lead time shortened because the part is finished when it leaves the Swiss cell, and cost came down for the same reason.

Yield is stable across releases because the process is documented for both alloys and because the inspection that proves it is automated rather than dependent on who is at the bench. The customer orders against a schedule and receives lots that arrive complete, measured and documented.