The Guide Bushing Is the Process
In Swiss type turning the workpiece is held by a guide bushing a few millimetres from the cutting tool, so the tool never pushes against an unsupported length. That single detail is why a 1 mm pin can be turned 40 mm long without bending, while the same part on a conventional lathe deflects away from the tool and tapers.
The bushing is matched to the bar stock, not to the finished diameter. Bar is bought ground to h9, and bar that varies in diameter is rejected rather than machined around, because it will either seize in the bushing or rattle in it.
What 0.005 mm Actually Requires
- Bushing clearance 0.005 mm to 0.01 mm, replaced on a wear limit rather than after a part fails.
- Support from both main and sub spindle, so the part is never unsupported during cut off.
- Measurement at 20 degrees Celsius with a micrometer at three positions along the pin.
- Roundness verified on a talyrond where the fit is critical, with the trace supplied on request.
- In process checks every 50 pieces, not only at the start and end of the batch.
| Feature | Capability | Note |
|---|---|---|
| Diameter | 0.8 mm to 12 mm | 0.005 mm tolerance on diameter |
| Straightness | 0.01 mm over 50 mm | The harder number on thin pins |
| Surface roughness | Ra 0.4 | Wiper insert plus light finish pass |
| Cross holes | From 0.4 mm | Drilled and deburred from sub spindle |
Secondary Operations Without a Second Setup
Cross holes, rolled threads, slots, flats and hex features are completed in the same cycle using the C axis and the sub spindle. Every operation moved into the main cycle removes a re-chuck, a handling step and a new source of position error, which matters more on small parts than on large ones because the handling damage is proportionally larger.
Where Swiss Turning Stops
The process is limited by length to diameter ratio and by bar size. Beyond about twenty to one, guidance and vibration become the constraint rather than tolerance. Materials matter too: titanium and beryllium copper demand different edge geometry and lower cutting speeds than 316L, and quoting them at stainless parameters produces scrap.
Capability and material options are listed on the Swiss type turned pin page.
