How to Read Any Carbide Insert Code (ISO 1832 Decoded)

Carbide insert codes look like gibberish until you realize each character is a coordinate — shape, clearance, tolerance, style, size, thickness, corner. Once you read them, you can walk into any toolstore and spec exactly what you need. This post decodes the most-common turning and milling insert codes.

Turning insert codes (ISO 1832)

Turning insert codes are 7 to 9 characters. Example: CCMT060204.

Position 1 — Shape

• C — 80° diamond | D — 55° diamond | V — 35° diamond
• W — 80° trigon | T — triangle | S — square | R — round
• K — 55° parallelogram | L — rectangle | A — 85° parallelogram
• H — hexagon | O — octagon | P — pentagon

Position 2 — Clearance angle

• N — 0° (negative rake, strongest)
• A — 3° | B — 5° | C — 7° | P — 11° | D — 15° | E — 20° | F — 25° | G — 30°

Higher clearance = freer cutting, finer finishes, lower cutting force. Lower clearance = stronger edge.

Position 3 — Tolerance class

• A, B, C, F — tighter tolerances (precision ground)
• M, U — medium tolerance (most common in industry)
• G, J, K, L, N — specialised tolerances

Position 4 — Style / chipbreaker

• A — with hole, no chipbreaker
• G — with hole, chipbreaker both sides (double-sided insert)
• M — with hole, chipbreaker one side
• T — with hole, chipbreaker one side, top only (most common for CCMT-style)
• W — with hole, chipbreaker one side (alternative style)
• R — no hole, no chipbreaker
• N — no hole, chipbreaker
• X — user-specified / non-standard

Position 5–6 — Cutting edge length (mm ÷ 10)

For CCMT060204: 06 means 6.35 mm cutting edge length (they round to ISO-standard inch-derived sizes).

Common sizes: 06 (6.35 mm), 09 (9.525 mm), 12 (12.7 mm), 16 (15.875 mm), 19 (19.05 mm).

Position 7–8 — Thickness (mm ÷ 10)

For CCMT060204: 02 means 2.38 mm thickness.

Position 9–10 — Corner radius (mm ÷ 10)

For CCMT060204: 04 means 0.4 mm corner radius.

Common: 02 (0.2), 04 (0.4), 08 (0.8), 12 (1.2), 16 (1.6), 24 (2.4).

Milling insert codes (slightly different)

Milling inserts like APMT1604, APKT1604, or RPMT1204 follow a similar logic:

• Position 1–2: Shape + mounting style (AP = parallelogram, RP = round, SP = square)
• Position 3: Clearance (M = 11°, K = 15°)
• Position 4: Tolerance (T = medium)
• Position 5–6: IC / cutting edge length
• Position 7–8: Thickness
• Position 9+: Often includes chipbreaker + grade suffixes (like PDR, PDER, MOE)

Suffixes after the core code

Many inserts carry extra suffixes after the ISO core. These are manufacturer conventions, not ISO:

• Grade — AX3150, NC3120, VP15TF, LF6118 — the substrate/coating name
• Chipbreaker geometry — HQ, FG, MV, WM, EM, TM (each brand has its own naming)
• Application hints — -MS (medium stainless), -FG (fine finishing), -TM (tough medium), -PM (precision milling)

A worked example

VBMT160404-TM AX3150:

• V — 35° diamond shape
• B — 5° clearance
• M — medium tolerance
• T — with hole + chipbreaker on top
• 16 — 16 mm cutting edge length
• 04 — 4.76 mm thickness
• 04 — 0.4 mm corner radius
• TM — tough-medium chipbreaker
• AX3150 — grade (Atomix finishing grade for steel/cast iron)

Why this matters for buyers

Once you read an insert code, you can:

• Swap brands while keeping the same ISO code (Atomix VBMT160404 fits the same holder as Mitsubishi VBMT160404)
• Spot when someone hands you the wrong insert (wrong size, wrong clearance)
• Order confidently over phone or WhatsApp without sending photos
• Read brand application charts accurately — they all use the same ISO base

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