Understanding ISO Turning Insert Designation: WNMG080412 Explained -

In our previous article, we broke down CNMG120412 — a diamond-shaped negative insert. This time, we’re decoding WNMG080412, a trigon-shaped insert with a different geometry and trade-offs. Same method: real photos, position by position.

W — Shape: Trigon (80° Included Angle)

The first letter, “W,” indicates a trigon shape — a three-sided insert with an 80° included angle at each tip, shown marked below. Unlike the diamond-shaped CNMG insert (2 usable edges), a trigon gives you three cutting edges per insert, which can reduce tooling cost over high-volume runs.

**Left:** the WNMG080412 insert as-is. **Right:** the ~80° included angle marked at one tip — the defining feature of the “W” shape code.

N — Clearance Angle: 0° (Negative Insert)

Just like our CNMG120412 insert, the second letter “N” means this is a negative insert with a 0° clearance angle. The side wall sits perfectly vertical, meaning both the top and bottom faces can be used as cutting surfaces — combined with the trigon shape’s three edges, this gives you six total usable cutting edges from one insert.

**Left:** side profile of the WNMG080412 insert. **Right:** the wall marked to show its 0° angle, confirming this is a negative insert.

M — Tolerance Class M

Just like our CNMG120412 insert, the third letter “M” specifies a standard tolerance class — consistent, general-purpose dimensional precision suitable for everyday turning operations.

G — With Hole, Chipbreaker on Both Faces

Same combined designation as CNMG120412 — “G” means a cylindrical hole for clamping, paired with a chipbreaker groove molded on both faces. Below, the same insert shown as-is, with the center hole marked, and with the chipbreaker groove marked.

**Left to right:** WNMG080412 as-is, center hole highlighted, chipbreaker groove highlighted — both features together represented by the “G” code.

08-04-12 — Size, Thickness, and Corner Radius

The first pair, “08,” refers to the inscribed circle size — 9.525mm (3/8″) in this case. As with our CNMG article, remember: this is the diameter of a circle touching all edges of the shape, not the length of a cutting edge itself.

**Left:** the WNMG080412 insert as-is. **Right:** the inscribed circle marked in green, calculated from the triangle’s true geometry — this circle’s diameter is what the size code “08” refers to.

The second pair, “04,” specifies the thickness — 4.76mm from top face to bottom face, same as our CNMG120412 insert.

**Left:** side profile of the WNMG080412 insert. **Right:** the thickness marked in purple, corresponding to the “04” in the code.

The final pair, “12,” specifies the corner radius — 1.2mm, visible in the close-up below.

**Left:** close-up of one corner of the WNMG080412 insert. **Right:** the tip marked, showing the radius referenced by the final “12” in the code.

Coming Up Next

We’ve now covered both CNMG120412 and WNMG080412 in detail. In our next article, we’ll break down CCMT09… — a positive insert with a completely different geometry. Stay tuned.

Understanding ISO Turning Insert Designation: WNMG080412 Explained