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Description
TNMG 220408 turning insert – indexable 60° triangle
| Technical data | |
|---|---|
| Side length l | 22.0 mm |
| Insert thickness s | 4.76 mm |
| Hole diameter d1 | 5.16 mm |
| Corner radius rε | 0.8 mm |
| ANSI code | TNMG 432 |
| Carbide grade | S20 (ISO P20) |
Cutting data for the TNMG 220408 insert for steel, cast steel, and malleable cast iron
semi-finishing and roughing — ISO P and K groups
| Material | Semi-finishing | Roughing | ||||
|---|---|---|---|---|---|---|
| Vc [m/min] | Feed f [mm/rev] | ap [mm] | Vc [m/min] | Feed f [mm/rev] | ap [mm] | |
| PSteel | 100-150 | 0.2-0.4 | 1.5-4 | 60-100 | 0.3-0.6 | 3-8 |
| PCast steel | 80-120 | 0.2-0.4 | 1.5-4 | 50-90 | 0.3-0.5 | 3-6 |
| KMalleable cast iron | 70-110 | 0.15-0.35 | 1.5-4 | 50-80 | 0.25-0.5 | 3-6 |
S20 carbide indexable insert – applications and design
double-sided 60° triangle with a hole and chip breaker
The TNMG 220408 turning insert is a double-sided, triangular indexable insert made of uncoated cemented carbide in grade S20, designed for turning steel, cast steel, and malleable cast iron. Shape T denotes an equilateral triangle with a corner angle of 60°, providing easier access to the workpiece profile during longitudinal turning and facing. The negative geometry with a clearance angle of 0° allows both sides of the insert to be used — a total of six cutting edges. The nose radius rε of 0.8 mm combines a good surface finish with cutting edge strength at feed rates of 0.2–0.4 mm/rev. The mounting hole with a chip breaker on both sides (type G according to ISO 1832) controls chip flow and breaking.
Key features of the S20 carbide insert
- Six cutting edges — 3 corners on each of the two sides reduce the cost per cutting edge compared with single-sided inserts.
- Uncoated grade S20 (ISO P20) — carbide for finishing and semi-finishing steel and cast steel at high speeds and moderate feed rates.
- Corner radius rε 0.8 mm — a general-purpose option between finishing (0.4 mm) and roughing (1.2 mm) in the same family.
- Tolerance class M provides repeatable cutting edge positioning after indexing the insert in the holder pocket.
- Dimensions according to ISO 1832: cutting edge length 22 mm, IC 12.7 mm (1/2″), thickness 4.76 mm — compatible with holders with a 22 pocket.
- A corner angle of 60° produces lower radial forces than a 80° corner, reducing vibration on slender workpieces.
Cutting parameter selection and applications of the triangular insert
The TNMG 220408 insert (also written without a space as tnmg220408) is suitable for turning shafts, bushings, and flanges made of structural steels, steel castings, and malleable cast iron components. Calculate spindle speed using n = 1000·Vc/(π·D): for a shaft diameter of 80 mm at Vc = 120 m/min, the result is approximately 477 rpm. For cast steel, maintain a cutting speed of 80–120 m/min and a constant feed rate to reduce thermal loads on the uncoated cutting edge. Indexable inserts in grade S20 are supplied by the Polish manufacturer Baildonit as an economical cutting option for standard steel and cast steel machining.
The triangular 60° profile has a compact, strong corner that withstands entry into the material and lightly interrupted cuts. The hole with a chip breaker curls chips into short segments, making them easier to evacuate from the groove and protecting the machined surface. The double-sided design uses all six cutting edges, keeping the actual cost per edge low in series production. Rigid clamping with a screw through the insert hole reduces vibration and helps maintain repeatable workpiece dimensions. For structural steel, start at moderate speeds and increase the feed rate only after evaluating chip formation. For finishing, select higher speeds from the table; for roughing, increase the depth of cut ap and the feed rate.
▲
Application limitation
Grade S20 is uncoated, so it has lower abrasion and heat resistance than coated grades. For prolonged cutting at high speeds, highly abrasive materials, or steels hardened above 45 HRC select a coated grade or a variant CBN.
Triangular insert designation decoder according to ISO 1832
how to read the TNMG 220408 code — positions 1–7 of the designation
Designation TNMG 220408 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.
Compatible turning tools
holders with a triangular 22 pocket (IC 12.7 mm) — external and internal turning
TTJNR/L 2525 M2225×25 × 150 mmR right-hand
←L left-hand
→
←L left-hand
→
TTJNR/L 3232 P2232×32 × 170 mmR right-hand
←L left-hand
→
←L left-hand
→
TTJNR/L 4040 S2240×40 × 250 mmR right-hand
←L left-hand
→
←L left-hand
→
TTENN 2525 M2225×25 × 150 mmNeutral
↔
↔
TTENN 3232 P2232×32 × 170 mmNeutral
↔
↔
TTENN 4040 S2240×40 × 250 mmNeutral
↔
↔
TTGNR/L 2525 M2225×25 × 150 mmR right-hand
←L left-hand
→
←L left-hand
→
TTGNR/L 3232 P2232×32 × 170 mmR right-hand
←L left-hand
→
←L left-hand
→
TTGNR/L 4040 S2240×40 × 250 mmR right-hand
←L left-hand
→
←L left-hand
→
TTFNR/L 2525 M2225×25 × 150 mmR right-hand
←L left-hand
→
←L left-hand
→
TTFNR/L 3232 P2232×32 × 170 mmR right-hand
←L left-hand
→
←L left-hand
→
TTFNR/L 4040 S2240×40 × 250 mmR right-hand
←L left-hand
→
←L left-hand
→
MTJNR/L 2525 M2225×25 × 150 mmR right-hand
←L left-hand
→
←L left-hand
→
MTJNR/L 3232 P2232×32 × 170 mmR right-hand
←L left-hand
→
←L left-hand
→
MTJNR/L 4040 S2240×40 × 250 mmR right-hand
←L left-hand
→
←L left-hand
→
MTENN 2525 M2225×25 × 150 mmNeutral
↔
↔
MTENN 3232 P2232×32 × 170 mmNeutral
↔
↔
MTENN 4040 S2240×40 × 250 mmNeutral
↔
↔
S32T TTUNR/L-22ø32 × 300 mm | D min ≥40R right-hand
←L left-hand
→
←L left-hand
→
S40U TTUNR/L-22ø40 × 350 mm | D min ≥50R right-hand
←L left-hand
→
←L left-hand
→
S50V TTUNR/L-22ø50 × 400 mm | D min ≥63R right-hand
←L left-hand
→
←L left-hand
→
S32T MTUNR/L-22ø32 × 300 mm | D min ≥40R right-hand
←L left-hand
→
←L left-hand
→
S40U MTUNR/L-22ø40 × 350 mm | D min ≥50R right-hand
←L left-hand
→
←L left-hand
→
Frequently asked questions about the TNMG 220408 insert
use, turning tool selection, and turning parameters
Six — the triangle has 3 corners per side, and the negative geometry (clearance angle of 0°) allows both sides of the insert to be used. Once an edge is dull, simply rotate the insert in its pocket without replacing the holder.
Holders with a 22 triangular pocket (IC 12.7 mm): for external turning TTJNR/L and MTJNR/L (entering angle 93°), TTFNR/L and TTGNR/L (90°) and neutral holders TTENN and MTENN (60°) with shank cross sections of 25×25–40×40 mm; for internal turning, boring bars S32T–S50V with the suffix TTUNR/L or MTUNR/L.
Only in corner radius: 0.4 mm is used for finishing at low feed rates, 0.8 mm is the general-purpose version, and 1.2 mm is selected for roughing at higher feed rates. The remaining dimensions (IC 12.7 mm, thickness 4.76 mm) are identical.
Yes — the uncoated grade S20 covers group ISO P (steel, cast steel), and according to the cutting data table, also ISO K (malleable cast iron). For malleable cast iron, use a cutting speed of 70–110 m/min for semi-finishing and a constant feed rate.
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| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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