Precision Cutting Tools for Hard Materials
ENDERUES
  1. Home
  2. Applications
  3. Turning Mill Rolls with PCBN Inserts

Turning Mill Rolls with PCBN Inserts

Roll turning is the most demanding common application for PCBN. Workpieces are large, depths of cut are measured in millimetres rather than tenths, and the material is often a high-chromium or high-speed steel casting with scale and chilled zones.

Why roll turning is different

The scale of the operation changes the constraints. Cutting forces are large, interrupted cuts are the norm rather than the exception, and thermal cycling is severe. Machine rigidity and fixturing quality matter as much as insert grade, and a grade that performs well on a small diameter part may chip immediately on a roll.

Roll materials add further difficulty: high-chromium cast iron, high-speed steel and indefinite-chill iron rolls combine high hardness with hard inclusions and hard scale, and the roll body is rarely uniform across its length.

Roll types encountered

Common roll families include high-chromium cast iron rolls, high-speed steel rolls, indefinite-chill and grain iron rolls, forged steel rolls, and composite or spray-welded rolls where a hard surfacing layer sits over a softer body. Each demands a different compromise between wear resistance and impact resistance, and the transition from surfacing layer to base material is itself an interrupted cutting condition.

Grade direction

The dominant failure mode in roll turning is chipping from impact and thermal cycling, not progressive wear. Grade selection therefore errs toward toughness — a lower-CBN-content grade with ceramic binder and a strong edge — even at the cost of some wear resistance. This is the opposite of the choice that would be made for continuous cast iron turning.

Recommended cutting conditions for alloy and nodular cast iron (Koves catalogue)

Mill rolls are typically alloy cast iron, indefinite chill or nodular iron. The catalogue conditions for these material groups are listed below; the full gray cast iron table is on our gray cast iron application page.

Alloy / nodular cast iron — recommended cutting conditions (Koves catalogue)
OperationWorkpiece materialHardness (HB)GradeVc (m/min)f (mm/rev)ap (mm)
TurningAlloy cast iron> 200KBN800200–10000.1–0.6< 3.0
TurningNodular cast ironQT450–QT550 / QT600–QT700KBN98080–2000.1–0.4< 3.0
TurningNodular cast ironQT450–QT550 / QT600–QT700KBN800150–4000.1–0.4< 0.5

Parameter guidance

Roll turning rewards conservative speeds combined with substantial depth of cut. Increasing depth reduces the number of passes and total cutting time, which is usually the larger lever than cutting speed on a roll of this size.

Roll turning starting parameters (industry reference values — verify on your machine)
Roll typeHardnessVc (m/min)ap (mm)f (mm/rev)
High-chromium cast iron rollHSD 70–9060–1600.5–8.00.15–1.20
High-speed steel rollHSD 75–8850–1200.5–6.00.15–1.00
Indefinite chill iron rollHSD 60–7570–1800.5–6.00.20–1.20
Forged steel rollHB 200–300120–3001.0–8.00.20–1.50
Spray-welded / surfaced rollHSD 60–8540–1200.3–3.00.10–0.60

Frequently asked questions

What type of insert is used for roll turning?
Roll turning typically uses solid CBN or PCBN inserts with a strong edge geometry — round or square shapes with negative rake — rather than thin brazed PCBN layers, because the operation is a heavy interrupted cut with a large depth of cut and the insert must absorb impact rather than maximise the number of edges.
What depth of cut is used on roll turning?
Depth of cut varies widely with roll type and machine capability. On high-chromium cast iron rolls, depths from roughly 0.5 to 8 mm are used with cutting speeds in the 60 to 160 m/min range and feeds from 0.15 to 1.20 mm/rev. Because roll grades and hardness vary considerably, parameters must be established on the actual workpiece.
Need help choosing a grade?

Send us your workpiece material, hardness and machine parameters. Our engineers will recommend the right grade and cutting data.

Request a quote