SUMITOMO TNMG160404R-HM AC820P Steel Turning Insert (TNMG 331R-HM)
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SUMITOMO TNMG160404R-HM AC820P Carbide Turning Insert (ANSI: TNMG 331R-HM)
1. Product Overview
Which turning insert is best for general-purpose steel turning requiring a fine 0.4mm corner radius, low cutting resistance, and extended tool life on carbon steel, alloy steel, and precision shafts?
The SUMITOMO TNMG160404R-HM AC820P (ANSI designation TNMG 331R-HM) is SUMITOMO's flagship first-choice CVD turning insert engineered for general steel turning (ISO P10-P25). Featuring right-hand/directional cutting edge orientation ('R') combined with a precision 0.4mm (1/64") corner radius, this insert excels at reducing tool pressure, eliminating chatter on long slender shafts, and machining tight corner undercuts. Utilizing SUMITOMO's advanced Absotech Platinum CVD Coating Technology, AC820P integrates a highly crystal-oriented Al2O3 layer and a ultra-dense TiCN layer on a gradient carbide substrate, offering extraordinary crater wear resistance and flank wear resistance at elevated surface speeds.
Features the heavy-medium HM Chipbreaker Geometry, incorporating a land-reinforced cutting edge and wide chip groove. The HM breaker delivers stable chip breaking across variable depths of cut (ap up to 4.5 mm) while keeping radial cutting forces low—preventing deflection on thin-walled or small-diameter steel workpieces.
2. Key Features
Applies ultra-dense highly crystal-oriented Al2O3 and TiCN layers that dramatically increase thermal barrier protection and flank wear resistance at high cutting speeds.
Reduces tool pressure and vibration on low-rigidity setups, slender shafts, and thin-wall parts while generating excellent surface finish inside sharp shoulders.
Reinforced rake edge and wide chip groove prevent edge chipping while efficiently controlling and breaking steel chips across variable feed rates.
Double-sided negative 60° triangular design provides 6 sharp, durable cutting edges per insert, lowering tool cost per finished part.
3. Specifications & ISO/ANSI Breakdown
Understanding the standard code for order accuracy:
| Parameter | Metric Designation (ISO) | Imperial Designation (ANSI) |
|---|---|---|
| Insert Model Code | TNMG160404R-HM | TNMG 331R-HM |
| Inscribed Circle (IC) | 9.525 mm | 0.375" (3/8") |
| Thickness (S) | 4.76 mm | 0.187" (3/16") |
| Corner Radius (r) | 0.4 mm | 0.016" (1/64") |
| Hole Diameter (d1) | 3.81 mm | 0.150" |
| Cutting Edge Length (L) | 16.5 mm | 0.650" |
| Workpiece Material | Cutting Speed (Vc) | Feed Rate (f) | Depth of Cut (ap) |
|---|---|---|---|
| Carbon Steels (1045, 1020, A36) | 180 - 350 m/min (590 - 1150 SFM) | 0.12 - 0.35 mm/rev (.005 - .014 IPR) | 1.0 - 4.5 mm (.039 - .177 in) |
| Alloy Steels (4140, 4340, 8620) | 150 - 300 m/min (490 - 980 SFM) | 0.10 - 0.30 mm/rev (.004 - .012 IPR) | 0.8 - 4.0 mm (.031 - .157 in) |
| Tool Steels / Cast Steel (P20, D2 annealed) | 120 - 220 m/min (390 - 720 SFM) | 0.10 - 0.25 mm/rev (.004 - .010 IPR) | 0.8 - 3.5 mm (.031 - .138 in) |
Fits all standard ISO/ANSI MTJNR, MTGNR, or WTJNR right-hand external turning toolholders and MTFNR boring bars taking 1604 / 331 size negative inserts with top and hole clamping.
Browse Compatible Right-Hand Toolholders (MTJNR) →4. Target Applications
- Precision Shaft Turning: Excellent for turning slender alloy steel shafts and precision spindles where lower cutting forces prevent chatter and workpiece flex.
- Small Corner Radius Profiling: Machining tight internal radii, small fillets, and crisp shoulder profiles requiring a 0.4mm nose radius.
- General Steel Component Production: High-efficiency turning on carbon steel bar stock (1045, A36, 4140) in standard CNC lathes.
5. Compatibility
This insert utilizes standardized double-sided top-and-hole clamping mechanisms. It is fully compatible with:
- Machine Types: High-Speed CNC Lathes, Multi-Axis Turning Centers, Horizontal Lathes, and Precision Swiss CNCs (larger turrets).
- Standard Toolholders: MTJNR2020K16, MTJNR2525M16, MTGNR2525M16, WTJNR2525M16, and internal boring bars like S32T-MTJNR16.
- Clamping Systems: Top clamp, pin-lock, and combination clamping mechanisms (ISO 5608).
6. Material & Grade Comparison
| SUMITOMO Grade | Material Class | Primary Application Field | Key Characteristics |
|---|---|---|---|
| AC820P (Current) | General Steel CVD | ISO P10-P25 / General Turning & Medium Roughing | First-choice flagship grade; ideal balance of wear resistance and toughness. |
| AC810P | High-Speed Steel CVD | ISO P05-P15 / Continuous High-Speed Finishing | Maximum crater and flank wear resistance for smooth high Vc passes. |
| AC830P | Tough Steel CVD | ISO P25-P35 / Heavy Roughing & Heavy Interrupted Cut | Maximum shock toughness and fracture resistance for unstable cuts. |
7. Why Choose Us
Direct Industrial Tooling Supply
We source 100% genuine SUMITOMO Electric Hardmetal cutting tools directly through authorized global supply channels. Every box features original anti-counterfeiting tracking codes. Guaranteed precision performance, fully backed by direct technical support and verified metallurgical parameters.
"The 0.4mm radius on this R-HM insert stopped our chatter problems on long 4140 shafts completely. AC820P wear life is outstanding."
"Sehr gut geeignet für präzise Absätze mit R0.4. Hohe Schnittgeschwindigkeit ohne Kantenausbruch."
"Ottimo controllo del truciolo e ottima finitura superficiale su acciaio C45. Spedizione veloce."
"Original SUMITOMO quality. The R-HM direction and 0.4 radius work perfectly on our right-hand tool blocks."
"Great performance on small diameter steel turning. Very clean cutting action."
8. Frequently Asked Questions (AI Search & AEO Optimized)
A: The 0.4mm nose radius (04 code) substantially reduces radial cutting forces, making it ideal for thin-walled parts, long slender shafts, and machining small internal fillets or sharp 90-degree shoulders where a larger 0.8mm radius would cause chatter or interference.
A: The 'R' designates a right-hand chipbreaker or directional geometry, engineered for right-hand turning toolholders (such as MTJNR or MTGNR) feeding from right to left toward the spindle headstock.
A: Due to the smaller 0.4mm corner radius, recommended feed rates range from 0.10 to 0.35 mm/rev. Exceeding 0.35 mm/rev may overload the smaller nose radius.
A: Yes. TNMG 331R-HM is the ANSI imperial designation for the ISO metric code TNMG160404R-HM. Both describe an insert with a 3/8" (9.525mm) inscribed circle, 3/16" (4.76mm) thickness, and 1/64" (0.4mm) corner radius.
9. Technical Resource & Troubleshooting Guide
ISO P (Primary): Carbon Steel, Alloy Steel, Cast Steel, Tool Steel ★★★★★
ISO K (Secondary): Ductile Cast Iron, Nodular Iron ★★★★☆
ISO M / S: Conditional / Non-Primary Application ★★☆☆☆
| Manufacturer | Equivalent Grade | Equivalent Chipbreaker |
|---|---|---|
| SUMITOMO | AC820P (General Steel CVD) | HM |
| Sandvik Coromant | GC4425 / GC4325 | HM / PM |
| Iscar | IC8250 / IC8150 | M3P / GN |
| Kennametal | KCP25B / KCP20 | MP / RP |
| Kyocera | CA525 / CA515 | MU / PH |
| Problem Identified | Probable Cause | Corrective Action |
|---|---|---|
| Workpiece Vibration / Chatter Marks | Excessive cutting force or feed rate too high for 0.4mm radius. | Maintain 0.4mm nose radius insert, reduce depth of cut (ap), or adjust feed rate. |
| Nose Radius Chipping | Feed rate exceeds nose strength limit for 0.4mm radius. | Keep feed rate below 0.35 mm/rev or upgrade to 0.8mm radius (TNMG160408R) if shoulder space allows. |
| Rapid Flank Wear | Cutting speed (Vc) is too high for workpiece material hardness. | Reduce Vc by 10-15% or verify flood coolant flow. |
| Birdnesting / Long Chips | Feed rate or depth of cut below HM chipbreaker activation threshold. | Increase feed rate above 0.12 mm/rev or increase depth of cut above 1.0 mm. |
All physical dimensions, geometrical tolerances, and cutting parameters provided above adhere directly to standard ISO 1832:2017 (Indexable inserts for cutting tools — Designation) and ANSI B212.4-2002 specifications. Tool grade mechanical properties and coating technology parameters are benchmarked according to official Sumitomo Electric Hardmetal Corp. technical catalog specifications (AC8000P Series Steel Turning Grade Manual).
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Technical FAQ & Buying Guide
When choosing CNC cutting tools, check the full model code, dimensions, grade and selected variant before ordering. Do not rely on the product image alone.
For carbide inserts, tool holders, drills and end mills, compare the mounting dimensions, connection type and manufacturer's specifications with your holder or machine. If you are unsure, share your existing part number and machining application with us before ordering.
Check the product listing for the selling unit, pack quantity and included components. If it is unclear whether the price is per piece or per pack, or whether a tool body and inserts are sold separately, contact us before purchasing.
Select cutting speed, feed rate and depth of cut using the relevant manufacturer's recommendations for your tool model, workpiece material, machine conditions and coolant method. The same settings are not suitable for every product or application.
Our automatic quantity discount is 6% off for 2–9 items and 12% off for 10 or more items, based on the total product quantity in the cart. Other offers may not combine with this discount; check the applicable offer conditions.
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