Turned and milled in one setup: why the second clamping is the expensive one

Cross holes, flats, slots and hexagons no longer need a second machine. Doing them while the part is still in the first clamping removes a cost and an error at the same time.

A turned part with a cross hole used to be two jobs: turn it, then take the box of parts to a milling machine and locate every one of them again. Live tooling ended that. The drill or the mill sits in the same turret as the turning tools, and the feature is produced while the part is still held exactly where it was turned.

Why one setup is worth more than the saved handling

The obvious saving is the second machine and the second handling. The bigger one is the error you never make. Every re-clamping introduces its own position error, and that error adds to the ones already in the part. A cross hole drilled in the first clamping is referenced to the turned diameter directly; the same hole drilled after re-locating is referenced to whatever the fixture managed to find.

What can be done in the cycle

• Cross and angled holes, on and off centre
• Milled flats, hexagons and squares
• Slots, keyways and grooves
• Thread milling and thread whirling where a tapped thread is not suitable
• Polygon turning for hex and square drives

The back working spindle

The other half of the answer is the second spindle. As the part is parted off, it is caught by the back working spindle and machined on its cut-off face — facing, centring, drilling, a back thread — while the main spindle is already starting the next part. The component leaves the machine finished on both ends, without anyone having turned it round.

What it means for the drawing

Features that used to be expensive because they needed a second operation are now nearly free if they are reachable in the same cycle. A designer who knows this can put a flat or a cross hole where the assembly wants it, instead of where the old process allowed it. Worth asking about before finalising a drawing.

More on our machine park, or send a drawing to info@kovinski-izdelki.si.