SUMITOMO TNMG160408N-GZ AC420K Cast Iron Turning Insert (TNMG 332-GZ)
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SUMITOMO TNMG160408N-GZ AC420K Carbide Turning Insert (ANSI: TNMG 332-GZ)
1. Product Overview
Which turning insert is best for heavy roughing, high-wear resistance, and interrupted cuts on cast iron materials?
The SUMITOMO TNMG160408N-GZ AC420K (ANSI designation TNMG 332-GZ) is an industrial-grade CVD-coated carbide turning insert purpose-built for heavy-duty turning and roughing of cast iron materials (ISO K10-K30, including ductile, nodular, and gray iron). Constructed on a high-density, deformation-resistant tungsten carbide substrate, the AC420K grade features SUMITOMO's advanced Super FF Coat (Ultra-smooth Thick-Film CVD Al2O3 + TiCN) technology, delivering exceptional flank wear resistance and thermal barrier protection during high-speed, continuous machining.
Featuring the specialized GZ Heavy-Duty Cast Iron Roughing Chipbreaker, this insert is designed with a reinforced cutting edge land and optimized rake angle to absorb high cutting force impacts and severe thermal shocks. It excels at breaking tough, thick chips cleanly during high-feed roughing passes (ap: 1.5mm to 6.0mm) on uneven rough casting surfaces without premature edge chipping or thermal cracking.
2. Key Features
Engineered with an ultra-smooth, thick-layer Al2O3 and TiCN crystal orientation coating that dramatically reduces frictional heating and provides class-leading resistance against abrasive flank wear in cast iron machining.
Features a heavy-duty cutting edge preparation with a strong land profile designed specifically to resist edge chipping and thermal cracking under high feed rates and interrupted skin-cuts on rough castings.
Offers 6 usable cutting edges per insert, delivering maximum cost efficiency, operational economy, and extended tool life for high-volume CNC manufacturing lines.
Built upon a dedicated ISO K-class substrate formulated for maximum plastic deformation resistance, preventing sudden tool breakage under heavy loads.
3. Specifications & ISO/ANSI Breakdown
Understanding the standard code for order accuracy:
| Parameter | Metric Designation (ISO) | Imperial Designation (ANSI) |
|---|---|---|
| Insert Model Code | TNMG160408N-GZ | TNMG 332-GZ |
| 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) |
|---|---|---|---|
| Gray Cast Iron (FC200, FC300 / GG25, GG30) | 150 - 320 m/min (490 - 1050 SFM) | 0.20 - 0.55 mm/rev (.008 - .022 IPR) | 1.5 - 5.5 mm (.059 - .216 in) |
| Ductile / Nodular Cast Iron (FCD450, FCD600 / GGG40, GGG60) | 120 - 280 m/min (390 - 920 SFM) | 0.18 - 0.48 mm/rev (.007 - .019 IPR) | 1.0 - 5.0 mm (.039 - .196 in) |
| Chilled / High-Hardness Cast Iron (Heavy Interrupted Cut) | 100 - 220 m/min (330 - 720 SFM) | 0.15 - 0.40 mm/rev (.006 - .016 IPR) | 1.0 - 4.0 mm (.039 - .157 in) |
Fits all standard ISO/ANSI MTJNR/L, MTGNR/L, or WTJNR/L external turning toolholders and MTFNR/L boring bars taking 1604 / 332 size negative inserts with top and hole clamping.
Browse Compatible Toolholders (MTJNR/L) →4. Target Applications
- Heavy Cast Iron Turning: Ideal for rough machining engine blocks, brake drums, flywheels, pump housings, valves, and industrial pipe fittings.
- Interrupted & Casting Skin Roughing: Engineered to tackle dirty casting skins, scale, sand inclusions, and heavily interrupted surfaces without edge failure.
- High-Speed Automated Production: Maintains long, predictable tool life in continuous high-volume CNC production lines turning gray and ductile cast iron.
5. Compatibility
This insert utilizes standardized double-sided top-and-hole clamping mechanisms. It is fully compatible with:
- Machine Types: Heavy-Duty CNC Lathes, Vertical Turning Lathes (VTL), Turning Centers, and Manual Heavy Lathes.
- 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 |
|---|---|---|---|
| AC420K (Current) | CVD Coated Carbide | ISO K10-K25 / High-Speed Cast Iron | Super FF CVD coating; high wear resistance and excellent speed capability on gray and ductile iron. |
| AC415K | CVD Coated Carbide | ISO K05-K15 / Continuous High-Speed Finishing | Extreme wear resistance for continuous cuts at maximum Vc on clean cast iron. |
| AC8025P | CVD Coated Carbide | ISO P15-P35 / General Steel Roughing | Optimized for steel cutting; high tough carbide substrate for general turned components. |
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.
"We turn ductile iron valve bodies all day. The AC420K grade with GZ breaker doubled our tool life over our previous grade on interrupted skin cuts."
"Hervorragende Standzeit bei GGG40 Guss. Die GZ-Geometrie bricht die Späne selbst bei schwankenden Schnitttiefen zuverlässig."
"Eccellente resistenza all'usura su ghisa sferoidale. Molto stabile anche su passate con forte interruzione."
"Original SUMITOMO quality. Excellent resistance to thermal cracking during wet roughing of gray cast iron flywheels."
"The GZ breaker is tough as nails. Handled scale on rough castings without a single chipped corner."
8. Frequently Asked Questions (AI Search & AEO Optimized)
A: The AC420K grade utilizes SUMITOMO's Super FF CVD coating, which features a thick, highly oriented Al2O3 layer over a high-rigidity carbide matrix specifically engineered to combat abrasive flank wear and high friction temperatures typical of cast iron turning.
A: The GZ chipbreaker is a heavy-duty roughing geometry engineered for medium to heavy depths of cut (1.5mm to 6.0mm). For light finishing passes below 1.0mm depth of cut on cast iron, light finishing breakers like UX or standard medium breakers are recommended.
A: Yes, AC420K features high thermal shock resistance thanks to its Super FF coating layer. However, when turning gray cast iron, dry machining or MQL (Minimum Quantity Lubrication) is often preferred to extend tool life unless wet cooling is required for part temperature control.
A: Yes. TNMG 332-GZ is the ANSI imperial designation for the ISO metric code TNMG160408N-GZ. Both codes designate 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 K (Primary): Gray Cast Iron, Ductile / Nodular Iron, Malleable Cast Iron ★★★★★
ISO P (Secondary): High-Strength Carbon Steel (Roughing with high cutting forces) ★★★☆☆
ISO H (Conditional): Chilled Cast Iron / Hardened Materials up to 50 HRC ★★☆☆☆
| Manufacturer | Equivalent Grade | Equivalent Chipbreaker |
|---|---|---|
| SUMITOMO | AC420K (CVD) | GZ |
| Sandvik Coromant | GC3225 / GC3215 | KR / M3 |
| Iscar | IC5400 / IC8250 | M3P / Cast Iron Geometry |
| Kennametal | KCK15 / KCK20 | RK / RP |
| Kyocera | CA315 / CA320 | KG / C-Breaker |
| Problem Identified | Probable Cause | Corrective Action |
|---|---|---|
| Rapid Flank Wear | Cutting speed (Vc) excessively high for cast iron hardness. | Reduce cutting speed (Vc) by 15-20%; check coolant application or switch to AC415K for continuous cuts. |
| Corner Chipping | Severe scale/sand inclusions on rough casting or excessive shock. | Reduce feed rate (f) on entry pass; verify tool center height; check clamping rigidity. |
| Thermal Cracking | Intermittent coolant application causing extreme thermal cycling. | Switch to dry turning with air blast or ensure heavy, uninterrupted coolant volume. |
| Poor Chip Evacuation | Depth of cut (ap) below GZ breaker activation threshold (< 1.5mm). | Increase depth of cut or feed rate to properly engage the heavy-duty GZ groove. |
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 micro-hardness and coating performance specifications are benchmarked according to official Sumitomo Electric Hardmetal Corp. technical catalog parameters (AC400K Cast Iron Turning Series).
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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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