Swiss Machining — design guidelines
A sliding headstock lathe supports the bar in a guide bushing right at the cutting point, so slenderness stops being the limit. The trade is that the part has to come from bar stock and stay within the bushing's diameter range.
Constraints specific to this process
These are the limits that come from this process in particular. The general rules on wall thickness, corner radii and hole depth apply on top of them.
| Parameter | Design to thisNo surcharge, no discussion needed | We can reachAchievable, but affects price or lead time | Where the limit comes from |
|---|---|---|---|
| Bar diameter | 3 – 26 mm | 2 – 32 mm | Each guide bushing covers a narrow diameter band. A part outside our bushing set moves to a conventional lathe, where the slenderness limits come back. |
| Length-to-diameter | ≤ 20 : 1 | ≤ 30 : 1 | The bushing supports the bar where it matters, so 20:1 is routine — the same part on a chuck lathe would be impossible past about 4:1. |
| Smallest turned diameter | 0.8 mm | 0.3 mm | Below 0.3 mm the workpiece twists off under cutting torque. Between 0.3 and 0.8 mm we reduce feed and the cycle time roughly doubles. |
| Economic batch size | 500+ pcs | 100 pcs | Setting up a Swiss lathe takes hours — cam or CNC program, bushing change, bar loader. Below about 100 pieces a conventional lathe is cheaper despite the slower cycle. |
What we see go wrong most often
Recurring issues on the drawings that reach us. None of them are hard to avoid once you know to look for them.
- A large flange or head on an otherwise slim part. The bar has to be as thick as the flange, so almost all of it becomes chips and the material cost multiplies.
General machining rules
The numbers that apply across every cutting process — wall thickness, radii, holes, threads, tolerances and cost drivers.
- Wall thickness
- Internal corner radii
- Holes and threads
- Pockets, cavities and undercuts
- Tolerances, text and surface callouts
- What actually drives the price
Every quotation includes a manufacturability review against these rules. If something in your model falls outside them, we tell you before you commit, not after the first article fails.
Not sure whether your part clears these limits?
Send the STEP file. A manufacturing engineer marks up anything that will be difficult and returns it with the quotation — no charge, no obligation.