A sliding-head automatic is a CNC lathe with a moving headstock, in which bar stock is fed through a guide bush and the tool always cuts immediately behind it. Because the material is supported right at the point of cut, it does not deflect under cutting force — which makes it possible to machine long slender parts to tolerances in the thousandths of a millimetre. The machine is also known as a Swiss-type lathe, and the process as Swiss turning. They are the same thing.
This article explains how it differs from an ordinary lathe, what it actually delivers, and when it pays off for you — and when it does not.
How a sliding-head automatic works
The difference from a conventional lathe comes down to one thing, but a decisive one: where the material is supported.
On a CNC lathe the stock is clamped in the chuck and protrudes from it. The further from the chuck the tool cuts, the greater the leverage of the cutting force — and the bar begins to deflect. The practical limit is around three times the diameter; beyond it, accuracy falls off quickly and vibration appears.
The sliding-head automatic solves this differently:
- The bar passes through a guide bush that holds it close to the point of cut.
- The tool stays fixed and the headstock moves with the material, not the other way round.
- The distance between the support and the cutting edge therefore stays constant along the whole length of the part.
The cutting force has nowhere to create a bending moment. The length-to-diameter ratio stops being a limit — a part 5 mm in diameter and 100 mm long is routine work for this technology, while on a conventional lathe it is a problem.
Sub-spindle and driven tools
Modern sliding-head automatics have a sub-spindle that takes over the finished part and completes its back end. Added to that are driven tools — rotating mills and drills right in the turret.
The practical consequence: a part that would otherwise need turning, then milling on a second machine and drilling on a third, comes off the machine complete. It is not only about speed. Every re-clamping introduces a positional error; when the part is not re-clamped, that error never arises.
What the technology actually delivers
Published parameters for this class of machine (MM Průmyslové spektrum):
| Parameter | Value |
|---|---|
| Dimensional tolerance | 0.005 mm (Cp 1.33) |
| Roundness | 0.001 mm |
| Surface roughness | Ra 0.8 |
| Main and sub-spindle coaxiality | 0.01 mm |
| Tool change, cut to cut | 0.6 s |
| Tool capacity | up to 18 |
For scale: 0.005 mm is roughly one fifteenth the thickness of a human hair.
These are parameters of the technology according to machine builders and the trade press. The tolerance any supplier actually guarantees depends on the specific part, the material and the batch length — and they should confirm it before production starts, not after.
When it pays off and when it does not
The sliding-head automatic is not a better machine. It is a different machine for different parts.
It pays off when most of the following holds:
- Diameter up to roughly 40 mm. Machines are grouped by maximum bar diameter — typically 20 mm and 32 mm, with room to extend. Beyond that range the technology loses its point.
- The part is slender. Length markedly exceeds diameter — pins, shafts, mandrels, valve spools, contact pins, fasteners to drawing.
- Batches are in the hundreds and above. Setting up takes longer, but machining time per part is substantially shorter. Exactly how setup is absorbed into the unit price is shown in the article on the price of a turned part.
- The part has several operations. Turning plus cross holes, flats, grooves or threads — the machine handles all of it in one go.
- Repeatability matters. In a batch of a thousand, the last part must match the first.
It does not pay off when:
- You need single pieces. Setup will not be absorbed. A conventional lathe is cheaper.
- The diameter is well above 40 mm. Outside the range of the technology.
- The part is short and stocky. Flanges, discs, large-diameter bushings — a fixed-spindle lathe suits those better.
- The geometry is mostly non-rotational. Then it is work for a machining centre.
Material decides more than you expect
Sliding-head automatics are built for bar stock, and how the material behaves during cutting directly determines the price of the part.
Free-cutting steel behaves best — it has raised sulphur content, forms short brittle chips and spares the tooling. Stainless steel is tougher, the chip breaks less readily and machining time rises. Brass machines excellently, aluminium quickly, but it sticks to the cutting edge.
The price difference between materials is not driven by the bar price alone — often it matters more how long the machine spends on the part. More detail in the article on how material affects price and time.
How to tell a supplier who really has this technology
Plenty of shops advertise “CNC turning” and mean conventional fixed-spindle lathes. You can tell the difference from concrete figures:
- Do they name specific machine models? Sliding-head automatics come from a handful of Japanese and Swiss brands — Tsugami, Star Micronics, Citizen, Tornos. Those who have them usually name them.
- Do they state a diameter range? An answer like “Ø 3–35 mm” is different information from “small and large parts”.
- Do they mention a sub-spindle and driven tools? That determines how many operations fit into one setup.
- Will they say from what batch size it makes sense? Anyone who avoids the question either does not know or is selling you something else.
What Barluskat brings to this
We produce on six sliding-head automatics from the Japanese brands Tsugami and Star Micronics:
| Machine | Count |
|---|---|
| TSUGAMI B0325-II | 1× |
| TSUGAMI B0205-III | 2× |
| Star SR-32J | 2× |
| Star SR-20J | 1× |
The shop is completed by a 63 t hydraulic press.
Workpiece diameters Ø 3–35 mm, medium and large batches, materials free-cutting steel, stainless steel, aluminium, brass and steel tube. The company has been running since 2007 and its quality management system is certified to DIN EN ISO 9001.
We produce from 1,000 pieces; lead times are agreed for the specific order, because they depend on the material and on whether surface treatment is part of the delivery. We answer requests within 3–5 working days.
We supply the automotive, medical, control engineering and construction sectors.
Guaranteed dimensional tolerance and roughness we confirm for the specific part — they depend on material, geometry and batch length, so a general figure would be misleading. Send the drawing and we will tell you straight away whether the requirement is achievable, or where it could be relaxed without affecting function.
Do you have a drawing for a slender turned part up to Ø 35 mm? Send it to us for quotation — we will come back with price and lead time. An overview of our machinery and materials is on the Manufacturing page.