ISO 1832 Thickness and Nose Radius Codes
Positions 6 and 7 of an ISO 1832 designation are two-digit blocks that do not follow the same numbering rule. Thickness codes pick a standardised value; nose radius codes count tenths of a millimetre. This chart decodes every entry in both tables against the inserts catalogued on InsertBase.
Why the two blocks are numbered differently
In CNMG120408 the sixth and seventh positions are 04 and 08. They are read differently. Thickness (s) is a standardised code: 04 means 4.76 mm, not 0.4 mm, because the table stores the inch-derived thicknesses the industry stocks. Nose radius (rε) is a direct tenths-of-a-millimetre code: 08 means 0.8 mm.
That is why the same pair of digits can look like a decimal in one position and a size class in the other. For the size block that precedes them, see the ISO 1832 size code chart.
Thickness codes (position 6)
| Code | Thickness s | Inch | Catalogued inserts | Example |
|---|---|---|---|---|
| 01 | 1.59 mm | 0.063 in | 0 | — |
| 02 | 2.38 mm | 0.094 in | 33 | CCET060202 |
| 03 | 3.18 mm | 0.125 in | 62 | CNGG090304 |
| T3 | 3.97 mm | 0.156 in | 50 | CCET09T302 |
| 04 | 4.76 mm | 0.187 in | 156 | CCGT120402 |
| 05 | 5.56 mm | 0.219 in | 10 | CNMG120512 |
| 06 | 6.35 mm | 0.25 in | 45 | CNGA160612 |
| 07 | 7.94 mm | 0.313 in | 6 | CNMG250724 |
| 09 | 9.52 mm | 0.375 in | 5 | CNMG250924 |
Values are the metric equivalents of the standard thicknesses in the ISO 1832 table; inch figures are computed from millimetres. A count of 0 means the code is defined by the standard but no insert in this database publishes it yet.
The T-prefix thickness
One thickness code carries a letter: T3 is 3.97 mm (5/32 in), an intermediate value between 03 (3.18 mm) and 04 (4.76 mm). It still occupies the two characters of position 6, so a designation such as CNMG09T308 is read with no other change — the size block stays 09, the radius block stays 08. 50 catalogued inserts use this thickness.
Nose radius codes (position 7)
| Code | Nose radius rε | Inch | Catalogued inserts | Example |
|---|---|---|---|---|
| 00 | 0 mm (sharp corner) | — | 8 | DCET070200 |
| 005 | 0.05 mm | 0.002 in | 0 | — |
| 01 | 0.1 mm | 0.004 in | 2 | VCGT110301 |
| 02 | 0.2 mm | 0.008 in | 54 | CCET060202 |
| 04 | 0.4 mm | 0.016 in | 102 | CCET09T304 |
| 08 | 0.8 mm | 0.031 in | 102 | CCGT060208 |
| 12 | 1.2 mm | 0.047 in | 55 | CCGT120412 |
| 16 | 1.6 mm | 0.063 in | 27 | CNMA120416 |
| 20 | 2 mm | 0.079 in | 3 | SNMA120420 |
| 24 | 2.4 mm | 0.094 in | 13 | CNMG190624 |
| 30 | 3 mm | 0.118 in | 1 | VCGT220530 |
| X | special radius | — | 0 | — |
Code 00 marks a sharp corner or a round insert, where the effective corner radius is half the inscribed circle rather than zero. 005 and X are defined in the table but cannot appear in the standard two-character position; they are listed for completeness.
What the radius does to the cut
The nose radius is the radius of the rounded corner between the two cutting edges. A larger radius strengthens the corner and supports higher feed rates, at the cost of radial force and a greater tendency to chatter on slender work. A smaller radius reaches into profiles and shoulders more easily but concentrates load on a shorter edge. That trade-off is worked through in nose radius selection, and both numeric blocks are decoded together with the rest of the designation in the ISO 1832 decoder.
For the position-by-position reading of the whole standard, start with the designation walkthrough. The letters in positions 1–4 and the optional hand in position 8 are tabulated in the shape, clearance, tolerance and fixing code chart. If you know only the dimensions and not the code, browse the dimension set index by inscribed circle, thickness and nose radius instead.