Turning Inserts

Turning Insert Selection — Quick Reference

Turning inserts = INDEXABLE CARBIDE cutting tips for LATHE + CNC turning operations — replacing HSS lathe tools for production turning + finishing + high-volume machining. Indexable = fast tip change + multiple cutting corners per insert.

Critical: Match insert GEOMETRY + GRADE to material + operation — wrong = bad finish + tool breakage. Coating selection matters — AlTiN for steel + stainless; PVD for general; CVD for cast iron. Tool holder must match insert seat angle exactly. Brand: Seco — the only brand we stock in this category. Companion: indexable inserts, indexable turning, machinery.

Turning Inserts for Australian Lathe and CNC Turning

Turning inserts are the indexable carbide cutting tips used in lathe and CNC turning operations — replacing traditional HSS lathe tools for production turning, finishing, and high-volume machining. The indexable design allows fast tip rotation when one edge wears, with multiple cutting edges on each insert. For Australian production turning workshops, toolrooms, and CNC machining operations, the right turning insert matched to the operation, material, and tool holder is essential. AIMS Industrial supplies turning inserts exclusively from SECO.

The turning insert geometries we stock

• CNMG — 80° rhombic insert; the everyday workhorse for general turning
• DNMG — 55° rhombic insert; for profile work and finishing
• WNMG — 80° trigon insert; balanced cutting and finishing capability
• TNMG — 60° triangular insert; six cutting edges per insert
• SNMG / SCMT — square insert with 90° corners; eight cutting edges per insert
• VBMT / VNMG — 35° rhombic insert; for fine profile work
• RCMT — round insert; for profiling and finishing curved surfaces
• Threading inserts — see our thread turning inserts range

Choosing the right insert geometry

• General-purpose turning — CNMG (80° rhombic) is the most-used insert; balances strength and capability
• Profile and finish work — DNMG (55°) or VBMT (35°) for cleaner cuts on profiled work
• Heavy roughing — square or trigon inserts (SNMG, WNMG) for maximum cutting edges per insert
• Curved profiles — round inserts (RCMT) for ball-end and curve turning
• Threading — dedicated thread turning inserts

Insert grades — match to material

Insert grade selection is driven by workpiece material:

• P-grade — for steel, the most common grade in general workshop use
• M-grade — for stainless steel; toughness for work-hardening
• K-grade — for cast iron; short-chip cutting
• N-grade — for aluminium and non-ferrous; sharp edges
• S-grade — for high-temperature alloys (Inconel, titanium)
• H-grade — for hardened steels in finish turning

Coatings (TiN, TiCN, TiAlN, AlTiN) extend life on the more demanding grades.

Where turning inserts earn their place

• Production turning on CNC lathes — high-volume production where insert change time matters
• General lathe and turning centre work — versatile inserts for varied turning operations
• Toolroom and prototype work — quick insert changes between operations
• Heavy roughing — high stock removal in initial turning operations
• Finishing — surface quality matters more than speed

Insert designation explained

ISO insert designation (e.g. CNMG120408) encodes shape and dimensions:

• 1st letter (C) — insert shape (C = 80° rhombic)
• 2nd letter (N) — clearance angle (N = 0° / negative)
• 3rd letter (M) — tolerance class
• 4th letter (G) — fixing/clamping type
• Numerical (12-04-08) — size, thickness, and corner radius

Match the insert designation to the tool holder; substituting different geometries requires holder change.

Brands stocked at AIMS

SECO is the only brand AIMS stocks for turning inserts — engineered for production performance and consistent quality across the full geometry and grade range. For specialty inserts, large-quantity orders, or specific OEM requirements, our team can source through our distribution channels.

Companion ranges at AIMS

Turning inserts sit alongside our broader cutting tool range — see thread turning inserts, parting and grooving, milling inserts, and tool holder accessories for the related products.

Need help speccing turning inserts for production or toolroom turning? contact our team — we'll match insert geometry, grade, and tool holder.

People Also Ask — Turning Inserts

Q: What's the difference between a CNMG and a DNMG turning insert?

CNMG is an 80° rhombic insert and the everyday workhorse for general turning — it balances strength and capability. DNMG is a 55° rhombic insert used for profile work and finishing, giving a cleaner cut on profiled work than the more general-purpose CNMG.

Q: Which turning insert grade should I use for Inconel or titanium?

Use an S-grade insert for high-temperature alloys such as Inconel and titanium — a different grade again from the P-grade used for steel or the M-grade used for stainless, since these superalloys need a grade formulated specifically for high-temperature cutting conditions.

Q: What does the ISO designation CNMG120408 actually mean?

Each character encodes a specific attribute: the first letter is insert shape (C = 80° rhombic), the second is clearance angle (N = 0°/negative), the third is tolerance class (M), the fourth is the fixing or clamping type (G), and the numerical code (12-04-08) gives the size, thickness and corner radius. Matching the full designation to your tool holder is essential — a different geometry needs a different holder.

Q: Why would I choose a square or triangular insert like SNMG or TNMG over CNMG?

TNMG is a 60° triangular insert with six cutting edges, and SNMG is a square insert with 90° corners giving eight cutting edges — both offer more cutting edges per insert than the general-purpose CNMG, which makes them more economical for heavy roughing where you're cycling through edges faster.

Q: Do I need a coated or uncoated turning insert?

Coated carbide (TiN, TiCN, TiAlN or AlTiN) extends tool life on the more demanding grades and is the standard choice for production turning. Uncoated carbide is better suited to aluminium and finishing work, where the coating isn't needed and a sharper uncoated edge gives a better finish.