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Description
TNUN 220412 turning insert – indexable 60° triangle
| Technical data | |
|---|---|
| Side length l | 22.0 mm |
| Insert thickness s | 4.76 mm |
| Inscribed circle diameter IC | 12.7 mm |
| Corner radius rε | 1.2 mm |
| ANSI code | TNUN 433 |
NT-25 cemented carbide indexable insert – applications and design
double-sided 60° triangle without a hole or chip breaker
The TNUN 220412 turning insert is a double-sided, triangular indexable insert made of NT-25 grade cemented carbide by the Polish company Baildonit. Shape T, an equilateral triangle with a 60° corner angle, facilitates access to the workpiece contour during longitudinal turning and facing. Negative geometry with a 0° clearance angle allows both sides of the insert to be used — a total of six cutting edges. The large nose radius rε of 1.2 mm strengthens the tip and supports roughing at higher feed rates.
The flat type N design, without a hole or chip breaker, provides the maximum mass of carbide behind the edge, increasing its strength when removing large machining allowances. The broad tolerance class U is an economical solution that allows greater variation in the position of the inscribed circle, which is acceptable for roughing. The inscribed circle diameter IC is 12.7 mm, or half an inch, and the insert thickness of 4.76 mm matches standardized triangular holder pockets of this size.
Key features of the NT-25 cemented carbide insert
- Six cutting edges — 3 corners on each of the two sides reduce the cost per cutting edge compared with single-sided inserts.
- Baildonit grade NT-25 — cemented carbide from a Polish manufacturer with over 35 years of experience, offering enhanced edge resistance under unfavorable machining conditions.
- Corner radius rε 1.2 mm — a strong tip for roughing and semi-finishing at higher feed rates.
- Type N according to ISO 1832: an insert without a hole or chip breaker, secured by a top clamp.
- Tolerance class U (broad) — an economical solution for roughing where the tightest edge positioning tolerances are not required.
- A 60° corner angle produces lower radial forces than a 80° corner — less vibration on slender workpieces.
Applications and parameter selection for the triangular insert
The TNUN 220412 insert (also written without a space as tnun220412) is suitable for turning shafts, discs, and flanges where edge resistance to impact loads matters. Calculate spindle speed using n = 1000·Vc/(π·D): with an example cutting speed of Vc = 150 m/min and a diameter of D = 50 mm, the result is approximately 955 rpm. Type N without a chip breaker means that chip flow is controlled by selecting the feed rate and depth of cut rather than by the insert geometry. According to the manufacturer's data, grade NT-25 is intended for turning steel, cast steel, and cast iron, including interrupted cuts under unfavorable operating conditions.
In shop practice, the TNUN 220412 indexable insert is used where cutting edge reliability takes priority over the finest surface finish. A constant feed rate and adequate cooling limit heat buildup at the edge and extend its life between indexing operations. Three corners on each side provide six fresh cutting edges from a single cemented carbide insert before replacement — a measurable saving in series production.
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Mounting limitation
Type N (without a hole) is secured by a top clamp. The insert TNUN 220412 cannot be mounted in a screw-clamp or lever-lock holder designed for inserts with a hole — select a holder with a top clamping arm or wedge.
Triangular insert designation decoder according to ISO 1832
how to read the TNUN 220412 code — positions 1–7 of the designation
Designation TNUN 220412 according to the standard ISO 1832: 4 letters describe geometry and construction, 3 numeric codes describe dimensions. Each field has a number, an icon, and a brief description.
Frequently asked questions about the TNUN 220412 insert
handling, clamping, and turning parameters
Six — the triangle has 3 corners per side, and the negative geometry (clearance angle 0°) allows both sides of the insert to be used. When a corner becomes dull, simply index the insert in the pocket without changing the holder.
The fourth letter of the code describes the design: N is an insert without a hole or chip breaker. It is secured by a top clamp (arm or wedge), and chip flow is controlled by selecting the feed rate and depth of cut.
The nose radius determines the application: 0.4 mm is used for finishing at low feed rates, 0.8 mm is the general-purpose version, and 1.2 mm as in TNUN 220412 strengthens the tip and is selected for roughing at higher feed rates. The other overall dimensions remain consistent with the same insert size.
According to data from the manufacturer Baildonit, grade NT-25 is intended for turning steel, cast steel, and cast iron. The large nose radius and strong edge favor roughing and semi-finishing, including interrupted cutting conditions. Select the exact cutting data to suit the workpiece material grade and setup rigidity.
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| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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