SUMITOMO TNMG160408L-HM AC820P Steel Turning Insert (TNMG 332L-HM)
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SUMITOMO TNMG160408L-HM AC820P Carbide Turning Insert (ANSI: TNMG 332L-HM)
1. Product Overview
Which turning insert is best for general-purpose steel turning, offering high wear resistance and stable chip breaking across carbon steel, alloy steel, and forged components?
The SUMITOMO TNMG160408L-HM AC820P (ANSI designation TNMG 332L-HM) is SUMITOMO's flagship first-choice CVD turning insert engineered for general-purpose to medium-heavy turning in steel (ISO P10-P25). Featuring left-hand/directional cutting edge orientation ('L') combined with SUMITOMO's advanced Absotech Platinum CVD Coating Technology, AC820P integrates a highly crystal-oriented Al2O3 layer and a specialized TiCN layer on a gradient carbide substrate. This unique architecture provides remarkable crater wear resistance and flank wear resistance while maintaining structural edge strength during continuous and light interrupted steel cuts.
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 high depths of cut (ap up to 5.0 mm), preventing birdnesting and reducing cutting forces during medium-roughing operations on carbon and alloy steels.
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.
Features a specialized gradient carbide substrate that balances edge sharpness, fracture toughness, and plastic deformation resistance under heavy loads.
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 | TNMG160408L-HM | TNMG 332L-HM |
| Inscribed Circle (IC) | 9.525 mm | 0.375" (3/8") |
| Thickness (S) | 4.76 mm | 0.187" (3/16") |
| Corner Radius (r) | 0.8 mm | 0.031" (1/32") |
| 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) | 0.20 - 0.50 mm/rev (.008 - .020 IPR) | 1.5 - 5.0 mm (.059 - .197 in) |
| Alloy Steels (4140, 4340, 8620) | 150 - 300 m/min (490 - 980 SFM) | 0.18 - 0.45 mm/rev (.007 - .018 IPR) | 1.2 - 4.5 mm (.047 - .177 in) |
| Tool Steels / Cast Steel (P20, D2 annealed) | 120 - 220 m/min (390 - 720 SFM) | 0.15 - 0.38 mm/rev (.006 - .015 IPR) | 1.0 - 3.8 mm (.039 - .150 in) |
Fits all standard ISO/ANSI MTJNL, MTGNL, or WTJNL left-hand external turning toolholders and MTFNL boring bars taking 1604 / 332 size negative inserts with top and hole clamping.
Browse Compatible Left-Hand Toolholders (MTJNL) →4. Target Applications
- General Steel Machinery Parts: Efficient turning of automotive drive shafts, steel axles, gears, and structural steel components.
- Medium-to-Heavy Steel Roughing: High metal removal rate (MRR) turning on carbon steel bar stock (1045, A36, 4140).
- Forged & Cast Steel Machining: Medium roughing passes on forged steel components with light scale or minor interruptions.
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 Vertical Turning Lathes (VTL).
- Standard Toolholders: MTJNL2020K16, MTJNL2525M16, MTGNL2525M16, WTJNL2525M16, and internal boring bars like S32T-MTJNL16.
- 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.
"AC820P is our main workhorse for 1045 steel turning. Tool life increased by 25% compared to our previous CVD inserts."
"Sehr gute Standzeit bei hoher Schnittgeschwindigkeit. Die Kombination aus AC820P und HM-Spanbrecher funktioniert hervorragend."
"Eccellente inserto per tornitura generale di acciai legati. Controllo truciolo costante anche su passate gravose."
"Authentic SUMITOMO quality. Very reliable grade for continuous production runs on steel shafts."
"The L-HM configuration gives us excellent chip breaking and tool life on our left-hand turning stations."
8. Frequently Asked Questions (AI Search & AEO Optimized)
A: AC820P is SUMITOMO's general-purpose first-choice steel turning grade (ISO P10-P25) offering superior speed capabilities and wear resistance. AC830P (ISO P25-P35) prioritizes higher fracture toughness for heavy interrupted cuts and rough scale.
A: The 'L' designates a left-hand chipbreaker or directional geometry, optimized for left-hand toolholders (like MTJNL or MTGNL) feeding towards the tailstock or facing direction in specific lathe configurations.
A: The HM (Heavy-Medium) chipbreaker operates optimally at feed rates between 0.20 mm/rev and 0.50 mm/rev, with depths of cut (ap) between 1.5 mm and 5.0 mm in carbon and alloy steels.
A: Yes. TNMG 332L-HM is the ANSI imperial designation for the ISO metric code TNMG160408L-HM. Both describe an insert with a 3/8" (9.525mm) inscribed circle, 3/16" (4.76mm) thickness, and 1/32" (0.8mm) 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 |
|---|---|---|
| Rapid Flank Wear | Cutting speed (Vc) exceeds optimal limit for high-speed steel turning. | Reduce cutting speed (Vc) by 10-15% or check coolant flow. |
| Crater Wear / Plastic Deformation | Excessive thermal load on rake face at high feed and speed combinations. | Decrease depth of cut (ap) or transition to high-speed AC810P grade. |
| Unbroken Stringy Chips | Feed rate or depth of cut below HM chipbreaker engagement threshold. | Increase feed rate (f) above 0.20 mm/rev or increase depth of cut (ap) above 1.5 mm. |
| Edge Micro-Chipping on Interrupted Cuts | Interruption impact exceeds standard CVD layer toughness limits. | Switch to the tougher AC830P grade designed specifically for heavy interrupted cuts. |
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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