A “grade” is the specific combination of carbide substrate and coating. Two inserts with identical geometry and identical shape can have completely different tool life because of the grade. This page explains what varies, and lists every grade we stock against its ISO 513 material group.
What varies between grades
1. Substrate — grain size and cobalt content
Tungsten carbide grains are held together by a cobalt binder. The trade-off is fixed by physics:
- Small grains + low cobalt → very hard and wear resistant, but brittle.
- Large grains + high cobalt → tough and shock resistant, but wears faster.
A finishing grade for steel is hard and fine-grained. A roughing grade for cast iron with sand inclusions is coarse and tough. There is no grade that is best at both.
2. Coating — CVD versus PVD
| CVD | PVD | |
|---|---|---|
| Deposition temperature | ~1000 °C | ~500 °C |
| Coating thickness | 5–20 µm (thick) | 1–5 µm (thin) |
| Edge condition | Rounded, slightly weaker | Sharp, strong edge |
| Wear resistance | Excellent | Good |
| Toughness | Lower | Higher |
| Typical use | Continuous cuts, high speed, steel and cast iron | Interrupted cuts, low speed, stainless and superalloys |
| Common layers | TiCN, Al2O3, TiN | TiAlN, AlTiN, TiSiN |
The alumina (Al2O3) layer in CVD coatings is the reason steel cutting speeds went up so much: it is a thermal barrier that keeps heat out of the substrate. PVD coatings are thinner and keep the edge sharp, which is why they dominate stainless, superalloys and milling.
3. Edge preparation
A perfectly sharp edge is also a fragile one. Manufacturers hone, brush or round the edge to a few hundredths of a millimetre. A heavily honed edge survives interrupted cuts; a lightly honed one cuts more freely and gives better finish. This is part of the grade, not the geometry.
How to read grade names
There is no universal standard for grade names — every manufacturer has its own system. But most follow a pattern: a prefix for the brand or series, digits that roughly indicate position in the range, and a suffix letter for the intended material group.
In our range you will see suffixes like P (steel), M (stainless), K (cast iron), S (superalloys), H (hardened), and U (universal). For example:
AC152P— Achteck, steel (P) orientedAC200M— Achteck, stainless (M)AC102K— Achteck, cast iron (K)AP100S— Achteck, superalloys (S)AP151H— Achteck, hardened steel (H)AP251U— Achteck, universal
The digit in the middle generally increases with toughness. So within one brand, a AC052P is harder and more wear resistant while AC252P is tougher — the higher number is the safer choice on interrupted cuts.
Every grade we stock, by material group
Below is the actual distribution from our catalogue — 40 distinct carbide grades across 4526 insert records. The count is how many insert records in stock are published for that group.
| Group | Grades stocked (most common first) |
|---|---|
| P Steel | AT210A, AC152P, AC052P, AC252P, AT202, AP251U, AC350P, AP403M, AP351U, AT210 |
| M Stainless | AP200U, AC200M, AC100M, AP200M, AP301M, AP251U, AP403M, AP351U, AP100S, AP100U |
| K Cast iron | AT202, AC102K, AC202K, AP251K, AC301K, AC100K, HS6120, AC151K, PB90, AC251P |
| N Non-ferrous | PD20, HS6120, HS7125, HS7225, HS8115, HS8125, AW100K |
| S Superalloys | AC200M, AC100M, AP200U, AP301M, AP403M, AP351U, AP100S, AP351M, AP403S, AP010S |
| H Hardened | PB30, PB60, AP153H, AP151H |
Choosing: the decision order
- Material group first. A P grade on Inconel will fail quickly regardless of geometry.
- Continuous or interrupted? Continuous → harder, more wear-resistant (CVD). Interrupted → tougher (PVD or high-cobalt).
- Roughing or finishing? Roughing → tougher, thicker coating. Finishing → sharper, harder, finer grain.
- Rigidity. A weak setup needs a tougher grade even if it costs tool life.
Two practical warnings
Do not mix grades between roughing and finishing and expect the same speeds. A finishing grade at roughing parameters will chip immediately.
Do not judge a grade on the first part. Carbide wear is not linear. Compare grades on flank wear after a fixed cutting time, at fixed parameters, on the same batch of material.
Related
- ISO 513 material groups explained
- Chipbreaker and geometry selection
- Turning insert selection guide
- Milling insert selection guide
Standards and further reading
The material group definitions used throughout this site follow ISO 513. The manufacturer links below are independent technical references.