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Carbide Insert Identification Chart
Every indexable turning insert carries its own spec sheet in its part number. This chart decodes the ISO 1832 designation one position at a time, then shows where CNMG, WNMG and TNMG inserts actually differ on the machine — so you can match a used insert, cross a competitor's part number, or pick the right shape for the next job.
Insert identification trips up experienced machinists for one reason: the code is positional, not descriptive. CNMG432 is not a model name — it is seven separate specifications written in order. Read it left to right and you get shape, clearance angle, tolerance, hole and chip-groove style, inscribed circle, thickness and nose radius. Anything after that belongs to the manufacturer: their geometry code and their carbide grade.
That is also why cross-referencing works. Two inserts carrying the same ISO block are dimensionally interchangeable in the same holder, even from different manufacturers — what changes is the substrate, coating and chip geometry behind the suffix. If you are holding an insert with a worn-off box, measure the inscribed circle and count the corners; that alone narrows it to a handful of designations.
How to read an insert part number
Worked example — CNMG432-RP KCP25: 80° rhombic, 0° clearance (negative, double-sided), medium tolerance, round hole with a chipbreaker on both faces, 1/2" inscribed circle, 3/16" thick, 1/32" nose radius, roughing geometry, P-grade steel carbide.
| Position | What it defines | Common values |
|---|---|---|
| 1 — Shape | Insert shape and included angle | C = 80° rhombic, W = 80° trigon, T = 60° triangle, D = 55° rhombic, S = square, R = round |
| 2 — Clearance | Relief (clearance) angle | N = 0° (negative, double-sided), C = 7°, P = 11°, G = 0° with ground tolerance |
| 3 — Tolerance | Dimensional tolerance class | M = medium (pressed, most common), G = ground/precision, U = utility |
| 4 — Hole / face | Hole style and chip-groove type | G = round hole with chipbreaker both faces, A = round hole no groove, W = 40-60° countersink |
| 5 — Size | Inscribed circle (IC), in 1/8" increments for inch inserts | 3 = 3/8" IC, 4 = 1/2" IC (metric uses cutting-edge length, e.g. 12 = 12 mm) |
| 6 — Thickness | Insert thickness, in 1/16" increments | 3 = 3/16", 4 = 1/4" |
| 7 — Nose radius | Corner radius, in 1/64" increments | 2 = 1/32" (0.8 mm), 3 = 3/64" (1.2 mm), 4 = 1/16" (1.6 mm) |
| 8+ — Suffix | Manufacturer's geometry and grade code | e.g. -RP, -MP, -LM roughing/medium/light geometry, then the grade: KCP25, MC6115, GC4325 |
CNMG vs DNMG vs WNMG vs TNMG
All four are negative, double-sided, medium-tolerance inserts with a chipbreaker — the letters that differ are the first one (shape) and what that does to corner strength and edge count. Filter by geometry, the job you are running, or what is on the shelf today, then jump straight to matching inventory.
Compare by geometry, application & stock
Included angle
Usable edges
Application
Stock status
| Designation | Shape | Edges | Corner strength | Where it wins | Stock |
|---|---|---|---|---|---|
| CNMG | 80° rhombic (diamond) | 4 usable corners | Strongest — thickest corner section | Roughing, interrupted cuts, forged or scaled stock, big depths of cut. | Ask us |
| WNMG | 80° trigon | 6 usable corners | Strong — 80° corners on a trigon body | Medium turning and facing on production runs where cost per edge rules. | Ask us |
| TNMG | 60° triangle | 3 (to 6) usable corners | Moderate — thinner 60° corner | Profiling, shoulders, tight corners and combined turn-and-face passes. | Ask us |
| DNMG | 55° rhombic (diamond) | 4 usable corners | Moderate — narrow 55° nose | Profiling, copy turning, contours and back-turning where reach matters. | Ask us |
80° rhombic (diamond) · 4 usable corners
Strongest — thickest corner section
Roughing, interrupted cuts, forged or scaled stock, big depths of cut.
80° trigon · 6 usable corners
Strong — 80° corners on a trigon body
Medium turning and facing on production runs where cost per edge rules.
60° triangle · 3 (to 6) usable corners
Moderate — thinner 60° corner
Profiling, shoulders, tight corners and combined turn-and-face passes.
Carbide grade groups (ISO colour codes)
The suffix after the ISO block is the grade, and it is matched to the workpiece, not the shape. The same CNMG432 body exists in every group below.
| Group | Workpiece material | What to expect |
|---|---|---|
| P (blue) | Steel, steel castings | CVD-coated carbide for continuous cuts; PVD when edges are interrupted |
| M (yellow) | Stainless, duplex, austenitic | Tough substrates with sharp PVD edges to fight built-up edge |
| K (red) | Grey and ductile cast iron | Hard, wear-resistant grades; thermal cracking is the usual failure |
| N (green) | Aluminium and non-ferrous | Uncoated or polished grades, often sharp-ground with high rake |
| S (brown) | Titanium and superalloys | Low cutting speeds, high-pressure coolant, fine-grain substrates |
| H (grey) | Hardened steel 45–65 HRC | Negative land geometries, light depth of cut, rigid setups only |
Identifying an insert with no box
- Count the corners and read the included angle — that gives you position 1.
- Measure the inscribed circle (the largest circle that fits inside the insert). 3/8" = size 3, 1/2" = size 4.
- Measure thickness in 1/16" steps: 3/16" = 3, 1/4" = 4.
- Check the nose radius against a radius gauge: 1/32" = 2, 3/64" = 3, 1/16" = 4.
- Look at the seat: a flat back with a chipbreaker on both faces means a negative (N) insert; a tapered side means positive.
- Send us the numbers and we will cross it. Text a photo to 440-966-1177 and we will tell you what fits and what we have on the shelf.
Recommended CNMG, DNMG, WNMG and TNMG inserts in stock
Now that the code makes sense, here is what is on the shelf in each shape — sealed, name-brand packs with the piece count and real savings against list shown on every card. Prices update as lots move.
Insert identification FAQ
How do I read a carbide insert part number?
Read it left to right in ISO 1832 order: shape, clearance angle, tolerance class, hole and chipbreaker style, inscribed circle size, thickness, nose radius, then the manufacturer geometry and grade suffix. In CNMG432-RP KCP25, C is an 80-degree rhombic shape, N is zero-degree clearance (negative, double-sided), M is medium tolerance, G is a round hole with a chipbreaker on both faces, 4 is a 1/2 inch inscribed circle, 3 is 3/16 inch thick, 2 is a 1/32 inch nose radius, and RP KCP25 is the roughing geometry and carbide grade.
What is the difference between CNMG, WNMG and TNMG inserts?
All three are negative, double-sided turning inserts, and they differ in shape and edge count. CNMG is an 80-degree rhombic with 4 usable corners and the strongest corner section, so it suits heavy roughing and interrupted cuts. WNMG is an 80-degree trigon with 6 usable corners, giving the lowest cost per edge on medium production turning. TNMG is a 60-degree triangle with 6 corners and the best access into profiles, shoulders and tight features, at the cost of a weaker corner.
How do I identify an insert when the box is gone?
Measure the inscribed circle with a caliper, count the cutting corners to determine the shape, measure the thickness and the corner radius, then check whether the insert has clearance on the side (positive, single-sided) or straight flanks (negative, double-sided). Those five measurements narrow it to a handful of ISO designations. Text a photo and the numbers to 440-966-1177 and we will cross it to what is in stock.
What do the carbide grade colour codes mean?
ISO groups material by application: P (blue) is steel, M (yellow) is stainless, K (red) is cast iron, N (green) is aluminium and non-ferrous, S (brown) is titanium and superalloys, and H (grey) is hardened steel above roughly 45 HRC. The grade code follows the geometry suffix, so KCP25 is a P-group steel grade and MC6115 is a coated steel grade from a different maker.
Are surplus carbide inserts the same quality as new inserts?
The inserts we sell as new surplus are unused, factory-sealed, name-brand stock from cancelled orders, overstock and shop closeouts — identical to what a distributor would ship, at up to 70 percent off list. Every listing states the condition grade, the brand, the piece count and the pack size before you buy.
Can I mix insert brands in the same toolholder?
Yes, as long as the full ISO designation matches through position seven — shape, clearance, tolerance, hole style, size, thickness and nose radius. Those positions define the seat geometry, so a CNMG432 from any maker will seat correctly. The geometry and grade suffix changes how it cuts, not whether it fits.
Keep going
- CNMG vs WNMG vs TNMG: the no-BS guide — when each shape wins, with in-stock equivalents for Kyocera, Sandvik and Kennametal part numbers.
- Turning tooling — boring bars and indexable holders to match the inserts above.
- Machine shop closeouts — full insert lots with condition grades and per-piece pricing.
- All charts, guides and buying references — the full resource library.
Know the code — now buy it for less
We stock factory-sealed, name-brand turning inserts pulled from cancelled orders and shop closeouts at 30–70% off list. Same designations your process sheet already calls out.