The ISO 1832 insert designation looks intimidating but encodes everything you need: shape, clearance, tolerance, hole, size, thickness, corner radius, and edge condition. Once you know the structure, you can read any insert code in 5 seconds.
The 8-Position Code Structure
Example: CNMG 12 04 08-MM
- Shape (1st letter) — Insert geometry
- Clearance (2nd letter) — Relief angle
- Tolerance (3rd letter) — Manufacturing precision
- Hole/chip breaker (4th letter) — Mounting and chip control
- Size (digits) — Cutting edge length
- Thickness (digits) — Insert thickness in mm
- Corner radius (digits) — Nose radius in 0.1mm
- Edge condition (letters) — Edge prep and chip breaker style
Position 1: Shape
| Code | Shape | Angle |
|---|---|---|
| C | Rhombic 80° | Best general-purpose turning, strong tip |
| D | Rhombic 55° | Profiling, finishing — sharp point |
| S | Square | Heavy roughing, 4 edges |
| T | Triangular | 3 edges, profiling, deep grooves |
| W | Trigon (3-corner) | Strong, vibration-resistant |
| R | Round | Heavy roughing, smooth surface |
| V | Rhombic 35° | Sharp profiling |
Position 2: Clearance Angle
- N — 0° (negative — strong, double-sided, most common)
- P — 11°
- C — 7° (positive, single-sided, lighter cuts)
- B — 5°
- D — 15°
Position 3: Tolerance Class
M = standard tolerance (most inserts).
G = ground precision (tighter for high-precision work).
U = looser, hot-pressed (rare).
Position 4: Hole and Chip Breaker
- G — Cylindrical hole + chip breaker on both sides
- M — Cylindrical hole + chip breaker on one side
- N — No hole, no chip breaker
- T — Countersunk hole + chip breaker
- R — No hole, chip breaker on one side
Decode the Example: CNMG 12 04 08-MM
- C — 80° rhombic
- N — 0° clearance (negative)
- M — Standard tolerance
- G — Cylindrical hole + double-side chip breaker
- 12 — 12mm cutting edge length
- 04 — 4.76mm thickness
- 08 — 0.8mm corner radius
- -MM — Medium chip breaker, medium operation
Translation: a general-purpose 80° rhombic negative insert, 12mm long × 4.76mm thick, 0.8mm corner radius — Walter’s/Sandvik’s most common turning insert.
Common Codes by Application
- CNMG 12 04 08 — General steel turning
- DNMG 15 06 04 — Stainless profiling
- CCMT 09 T3 04 — Light boring/finishing
- WNMG 08 04 08 — Heavy roughing, vibration-prone
- TNMG 16 04 12 — Heavy steel turning
Browse all standard ISO inserts at Hooguu’s insert catalog.
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