ISO 1832 Insert Size Code Chart: 04 to 31
The two digits in position 5 of an ISO 1832 designation are not the inscribed circle in millimetres — they are a standard size code whose metric value changes with the shape. This chart shows every code in the published table against the shapes it covers.
What the two-digit block encodes
In a designation such as CNMG120408, the third and fourth characters (12) are the cutting edge length code. The standard does not spell that number out in millimetres: it is a code, and the inscribed circle (d1) it corresponds to depends on the shape family's geometry. 12 on a rhombic 80° C insert is 12.7 mm, while 12 on a 35° V insert is 7.15 mm.
The values below are the metric anchors published in the ISO 1832 size table. Most of them are inch-derived — 6.35 mm is 1/4 in, 9.525 mm is 3/8 in, 12.7 mm is 1/2 in — which is why those anchors map cleanly to the ANSI shop-floor codes. Combinations the table does not cover are left unverified instead of estimated.
| Code | Inscribed circle by shape | Inch anchor | Catalogued inserts | Example |
|---|---|---|---|---|
| 04 | R 4 mm W 6.35 mm | 1/4 in | 5 | WCGT040204 |
| 05 | R 5 mm | — | 0 | — |
| 06 | R 6 mm C 6.35 mm W 9.525 mm | 1/4 in3/8 in | 21 | CCET060202 |
| 07 | V 4.76 mm D 6.35 mm | 1/4 in | 11 | DCET070200 |
| 08 | T 4.76 mm R 8 mm W 12.7 mm | 1/2 in | 10 | TPGX080202 |
| 09 | T 5.56 mm C 9.525 mm S 9.525 mm R 9.525 mm | 3/8 in3/8 in3/8 in | 39 | CCET09T302 |
| 11 | T 6.35 mm V 6.35 mm D 9.525 mm | 1/4 in1/4 in3/8 in | 48 | DCET11T300 |
| 12 | V 7.15 mm C 12.7 mm S 12.7 mm R 12.7 mm | 1/2 in1/2 in1/2 in | 61 | CCGT120402 |
| 13 | V 7.94 mm | — | 2 | VCGT130302 |
| 15 | D 12.7 mm S 15.875 mm | 1/2 in5/8 in | 40 | DCMT150404 |
| 16 | T 9.525 mm V 9.525 mm C 15.875 mm R 16 mm | 3/8 in3/8 in5/8 in | 76 | CNGA160612 |
| 19 | D 15.875 mm C 19.05 mm S 19.05 mm R 19.05 mm | 5/8 in3/4 in3/4 in3/4 in | 23 | CNMA190608 |
| 22 | T 12.7 mm V 12.7 mm | 1/2 in1/2 in | 21 | TCMT220508 |
| 25 | R 25 mm C 25.4 mm S 25.4 mm | 1 in1 in | 10 | CNMG250724 |
| 31 | R 31.75 mm | — | 0 | — |
Inch anchors are the six exact fractions named in the ISO 1832 table note. A blank inch cell means the entry is metric-only, not that the fraction is unknown. A count of 0 means the code is defined by the standard but no insert in this database publishes it yet.
Why the same code gives a different circle
The size code describes the cutting edge length l, and the inscribed circle follows from the shape: a 80° rhombic insert spends more of its edge length across the circle than a 35° rhombic insert does. That is why a 12 C-body is a 1/2 in insert while a 12 V-body is a 7.15 mm profiling insert. Machinists reading an ANSI code — where the size block is three digits such as 432 — are looking at the same underlying dimension, just written in inches.
If you have a full designation and want the shape, clearance, tolerance, fixing, thickness and radius decoded together, use the ISO 1832 decoder. For the position-by-position explanation, read the designation walkthrough, and for the shape choice itself see CNMG vs WNMG vs CCMT.
Where the catalogued inserts sit
Every size code above appears in the dimension set index as the exact inscribed circle × thickness × nose radius combinations that manufacturers publish, and in the full insert index. Inserts whose size block falls outside the published ISO table are not listed here — they stay on their own pages until the standard value is confirmed. The other two numeric blocks are decoded in the ISO 1832 thickness and nose radius code chart, and the letters in positions 1–4 are tabulated in the shape, clearance, tolerance and fixing code chart.