Turning technique: longitudinal and facing turning and cutter geometry
From the rotating workpiece to the faceplate designation — the basis for the journeyman exam's turning task
With turning, the workpiece rotates while the tool stands still and is guided along or into the workpiece. It is an effective way to make round, symmetrical parts — shafts, bushings, flanges and threads. On the journeyman's exam for CNC technician (level 2), a turning task is one of two individual manufacturing tasks, so turning technique must sit in your spine. It is about both understanding the operations and being able to read and choose the right tool.
§The basic operations
Longitudinal turning feeds the tool parallel to the part's axis and creates the cylindrical shape. Face turning feeds the tool perpendicular to the center and creates a flat end face. In addition, there is grooving (slot cutting) for grooves and parting, boring and internal turning for holes, and thread turning. Most parts are a combination: you face turn the end, longitudinally turn the diameter, cut a groove and cut a thread — often in one setup, which is a great strength of turning.
§Nose radius and adjustment angle
Two geometries on the tool matter especially. Nose radius is rounding on tool tip: larger radius gives stronger edge and smoother surface but also greater cutting force and risk of vibration in slender pieces. Rake angle determines how cutting force distributes and how thick chip becomes. When face turning you often choose slightly larger nose radius for surface while on slender shafts you keep radius and cutting force low to avoid piece bending away from tool
§Læs vendepladens ISO-betegnelse
Vendeplatter til drejning har en standardiseret ISO-kode (efter ISO 1832), der beskriver pladen — for eksempel CNMG 12 04 08. Hvert felt betyder noget: det første bogstav er pladens form (C = 80° rombe), det næste frivinklen (N = 0°), så tolerance og type, dernæst størrelsen, tykkelsen og til sidst næseradius (08 = 0,8 mm). Du behøver ikke kunne alle koder udenad, men det er guld værd at kunne læse formen og næseradius direkte af betegnelsen, når du står og skal vælge en plade.
| Operation | Movement | Result |
|---|---|---|
| Longitudinal turning | Parallel with the axis | Cylindrical diameter |
| Plane turning | Rectangular to center | Level end surface |
| Insertion | Radially into the component | Track or branch |
| Thread cutting | Synchronous with rise | External or internal thread |
§Stability is everything
Turning rewards rigidity. Slender workpieces that stick far out of the chuck bend under cutting force and give taper, vibration and poor surface. The solution is to support the workpiece with a centre or a steady rest (lunette), keep the overhang short and choose cutting data and tool nose radius that keep the cutting force down. Rigid clamping, a sharp cutter and well-chosen cutting data are the trinity that gives a clean, accurate turning job — and a good mark at the journeyman examination.
- 01Plan the end first so you have a clean reference to measure from
- 02Choose nose radius based on surface requirements and item slenderness
- 03Support slender components with center or live center.
- 04Lær at læse skærets ISO-betegnelse — især form og næseradius
- 05Short overhang and stiff clamping counteract cone and vibration
“Turning won't forgive mess: rigid workpiece, sharp cutter, right numbers.”