CNMG 120404 / CNMG 431, chip breaker BG, grade FM2553 — negative 80° rhombic turning insert.
1/2" inscribed circle, 3/16" thick, 1/64" corner radius. The BG breaker is the medium machining geometry: 0.008–0.016 ipr (0.2–0.4 mm/rev) at 0.06–0.16" (1.5–4 mm) depth of cut. FM2553 is a CVD (Al₂O₃) grade — tough substrate for heavy interrupted cuts in steel and stainless, heavy roughing in mild steel, and first choice for superalloys.
Specifications
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Insert designation (ISO): CNMG 120404
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Insert designation (inch): CNMG 431
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Insert shape: 80° rhombic (C)
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Clearance angle: 0° — negative (N)
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Tolerance class: M
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Insert type: G — with hole, chipbreaker both sides
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Inscribed circle (I.C.): 1/2" (12.7 mm)
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Thickness: 3/16" (4.76 mm)
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Corner radius: 1/64" (0.4 mm)
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Chip breaker: BG — Steel — medium machining
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Feed rate range: 0.008–0.016 ipr (0.2–0.4 mm/rev)
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Depth of cut range: 0.06–0.16" (1.5–4 mm)
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Grade: FM2553
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Coating: CVD (Al₂O₃)
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ISO application range: P20–P35 · M10–M30
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Cutting speed, non-alloy steel: 490–1150 SFM (150–350 m/min)
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Cutting speed, low-alloy steel: 300–980 SFM (90–300 m/min)
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Cutting speed, high-alloy steel: 230–820 SFM (70–250 m/min)
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Cutting speed, ferritic & martensitic stainless: 390–750 SFM (120–230 m/min)
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Cutting speed, austenitic stainless: 260–660 SFM (80–200 m/min)
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Cutting speed, titanium & super-alloys: 110–260 SFM (35–80 m/min)
Tool holders that accept this insert
69 RMC toolholders in stock take this insert — 80° rhombic, 0° — negative clearance, 1/2" inscribed circle, 3/16" thick. Pick by the shank your turret takes.
RMC square-shank toolholders — made in the USA
Boring bars and interchangeable heads. 66 more RMC tools take the same insert for internal turning. See RMC boring bars →
Grade & chip breaker selection chart →
Turning insert designations explained · Using a turning formula calculator
