FM Carbide Insert Grades & Chip Breakers Reference

Every FM Carbide insert title tells you four things: shape (CNMG), size (120404 metric / 431 inch), chip breaker (BF, BG, BR…) and grade (FM324, FM524…). This page decodes the last two so you can pick the right insert for your material and operation — no guesswork.

Chip Breakers: Match the Breaker to the Operation

The chip breaker controls how the chip forms, curls and breaks. Pick it by what you're cutting and how hard you're pushing — the profiles below go from light finishing grooves to deep roughing geometry:

Negative inserts (CNMG, TNMG, DNMG, WNMG…)

Code Profile Application Feed rate Depth of cut
-BF Steel — finishing 0.05–0.25 mm/rev (.002–.010 ipr) 0.5–1.5 mm (.02–.06")
-BL Steel — semi-finishing 0.1–0.3 mm/rev (.004–.012 ipr) 1–3 mm (.04–.12")
-BG Steel — medium machining 0.2–0.4 mm/rev (.008–.016 ipr) 1.5–4 mm (.06–.16")
-BC Steel — medium roughing & cast iron 0.2–0.5 mm/rev (.008–.020 ipr) 1.5–4 mm (.06–.16")
-BR Steel — roughing 0.3–0.6 mm/rev (.012–.024 ipr) 2–6 mm (.08–.24")
-BMF Stainless steel — finishing 0.07–0.3 mm/rev (0.003–0.012 ipr) 0.2–1.5 mm (0.01–0.06")
-BMM Stainless — medium & low-carbon steel 0.2–0.35 mm/rev (0.008–0.014 ipr) 1–3.5 mm (0.04–0.14")
-BMR Stainless steel — roughing 0.3–0.6 mm/rev (0.012–0.022 ipr) 1.8–5.5 mm (0.07–0.22")
…MA No chip breaker (grey cast iron) 0.2–0.6 mm/rev (.008–.024 ipr) 1–7 mm (.04–.28")

Positive inserts (CCMT, DCMT, TCMT, VCMT, VBMT…)

Code Profile Application Feed rate Depth of cut
-BF Finishing 0.05–0.2 mm/rev (.002–.008 ipr) 0.5–1.5 mm (.02–.06")
-BG Medium machining 0.15–0.3 mm/rev (.006–.012 ipr) 1–3 mm (.04–.12")

Grades: Match the Carbide to the Material

The grade is the carbide substrate + coating combination. Here's what each FM Carbide grade is built for:

Grade Coating ISO application range Built for
FM524
Turning 		CVD P01–P10K10–K25 Gray cast iron and very stable steel applications — the hardest substrate with CVD coating for extreme wear resistance.
FM2533
Turning 		CVD P05–P20K15–K35 Stable steel applications and nodular cast iron — a good balance between wear resistance and chipping resistance.
FM2538
Turning 		CVD P10–P25 Balanced productivity for continuous cuts — high wear resistance with improved toughness for high productivity with less trouble.
FM2543
Turning 		CVD P15–P30 The first-choice grade for general steel work — high flexibility from continuous cuts to interrupted cuts across various steel applications.
FM2553
Turning 		CVD (Al2O3) P20–P35M10–M30 Tough substrate for heavy interrupted cuts in steel and stainless, heavy roughing in mild steel — and the first choice when turning superalloys.
FM324
Turning 		PVD P10–P30M05–M25S05–S25H20–H40 The universal multi-purpose grade for mid and low cutting speeds — low-carbon steel, alloyed steel, stainless, cast iron, even Inconel and titanium alloys.
FM125
Milling & Drilling 		PVD P20–P35M10–M30K20–K40S15–S25 Multi-purpose milling and drilling grade — PVD coating with optimal thermal resistance and a tough carbide substrate for demanding applications.

ISO range chips read like this: lower numbers = harder, more wear-resistant applications; higher numbers = tougher, more demanding cuts. P steels · M stainless · K cast iron · S super-alloys · H hardened.

Cutting Speed by Grade and Material Group

Find your material group (ISO letter), then read across for each grade's recommended speed range:

ISO Material FM524 FM2533 FM2538 FM2543 FM2553 FM324 FM125
Milling		 FM125
Drilling
P Non-alloy steel 720–1570 560–1480 560–1340 590–1250 490–1150 390–820 460–1250 460–790
Low-alloy steel 720–1380 590–1250 430–1180 380–1150 300–980 230–750 390–980 390–720
High-alloy steel — 330–1080 260–1020 200–980 230–820 230–590 230–490 230–490
M Ferritic & martensitic stainless — — — — 390–750 200–590 390–660 390–660
Austenitic stainless — — — — 260–660 200–490 430–820 460–820
K Grey cast iron 560–1380 390–980 — — — 200–520 390–820 460–720
Nodular cast iron 390–1340 390–920 — — — 200–390 430–720 490–790
N Aluminum — — — — — — — —
S Titanium & super-alloys — — — — 110–260 110–200 80–150 —
H Hardened material — — — — — 130–260 130–260 —

ISO material groups: P steels · M stainless · K cast iron · N aluminum · S titanium & super-alloys · H hardened material. Quick orientation: FM524 runs the highest speeds in steels and cast iron; FM324 is the universal PVD grade — the one that also reaches titanium, super-alloys and hardened material; FM125 covers milling and drilling.

Still not sure? Tell us your material, operation and machine — we'll recommend a grade and chip breaker, machinist-to-machinist.

Ready to shop? Browse FM Carbide turning inserts (filter by shape with one click), all turning inserts, or FM Carbide milling inserts for FM125 applications.