CNMG 120408 Chip Breaker BG Grade FM2538 / CNMG 432 BG #FMCarbide

CNMG 120408 / CNMG 432, chip breaker BG, grade FM2538 — negative 80° rhombic turning insert.

1/2" inscribed circle, 3/16" thick, 1/32" 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. FM2538 is a CVD grade — balanced productivity for continuous cuts — high wear resistance with improved toughness.

Specifications

• Insert designation (ISO): CNMG 120408
• Insert designation (inch): CNMG 432
• Insert shape: 80° rhombic (C)
• Clearance angle: 0° — negative (N)
• Tolerance class: M
• Insert type: G — with hole, chipbreaker both sides
• Inscribed circle (I.C.): 1/2" (12.7 mm)
• Thickness: 3/16" (4.76 mm)
• Corner radius: 1/32" (0.79 mm)
• Chip breaker: BG — Steel — medium machining
• Feed rate range: 0.008–0.016 ipr (0.2–0.4 mm/rev)
• Depth of cut range: 0.06–0.16" (1.5–4 mm)
• Grade: FM2538
• Coating: CVD
• ISO application range: P10–P25
• Cutting speed, non-alloy steel: 560–1340 SFM (170–410 m/min)
• Cutting speed, low-alloy steel: 430–1180 SFM (130–360 m/min)
• Cutting speed, high-alloy steel: 260–1020 SFM (80–310 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 →

TURNING KNOW-HOW

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Practical guides to choosing, understanding and using your inserts.

01 / SELECTION

Grades & chip breakers

Explore the grade and chip-breaker selection chart for your turning operation.

Explore the chart → 02 / INSERT CODES

Know your insert

Understand turning-insert designations and what the letters and numbers mean.

Read the guide → 03 / CUTTING PARAMETERS

Turning calculations

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