Iscar SUMOTEC vs Sandvik CoroMill: Face Milling Cutter Comparison

Face milling is one of the most fundamental operations in CNC machining, responsible for creating flat surfaces on everything from engine blocks and gearbox housings to mold bases and machine tool components. The cutter body design, insert geometry, and grade selection all directly impact surface finish, metal removal rate, and cost per square meter of machined surface. Iscar’s SUMOTEC face milling system and Sandvik Coromant’s CoroMill platform are two of the most widely adopted solutions in the industry. This article compares their performance, versatility, and economics in production face milling applications.

Iscar SUMOTEC Face Milling System

Iscar’s SUMOTEC line features octagonal and round inserts designed for face milling of steel, cast iron, and stainless steel components. The SUMOMILL SM45 cutter, using SOMT 130520 octagonal inserts, provides 8 cutting edges per insert with a 45-degree lead angle that reduces radial cutting forces and directs chip flow away from the machined surface. This geometry is particularly beneficial when milling thin-walled components or when the machine tool has limited spindle power.

The SUMOTEC coating technology, applied to the IC808 and IC908 grades, uses a post-coating surface treatment that smooths the CVD Al2O3 layer and introduces compressive residual stresses. The IC808 grade (P15-P30) is the primary choice for face milling carbon and alloy steels, delivering cutting speeds of 200-380 m/min with feed rates of 0.15-0.40 mm/tooth. The IC908 grade (P20-P40) adds a tougher substrate for milling steel forgings and components with interrupted surfaces such as bolt holes and slots.

Sandvik CoroMill Face Milling Platform

Sandvik’s face milling portfolio is anchored by the CoroMill 345 and CoroMill 300 systems. The CoroMill 345 uses octagonal inserts (SEKN or SNEX types) with 12 cutting edges per insert, providing an outstanding cost-per-edge advantage in high-volume production. The 45-degree lead angle and positive axial rake geometry produce low cutting forces and excellent chip evacuation, making it suitable for both roughing and semi-finishing passes on steel and cast iron.

The CoroMill 300 system uses round inserts for profile milling and face milling of complex surfaces, offering true multi-axis capability for 5-axis machining centers. For dedicated face finishing, the CoroMill 365 with wiper inserts achieves surface finishes below Ra 0.8 um in a single pass, eliminating the need for secondary grinding or lapping operations. Sandvik’s GC4235 and GC3225 grades cover the full range of face milling applications in steel and cast iron respectively.

Face Milling Cutter Comparison

Metal Removal Rate Analysis

Metal removal rate (MRR) is the key productivity metric in face milling. For a 100 mm diameter cutter face milling 42CrMo4 steel at ap = 4.0 mm and ae = 80 mm, the Iscar SUMOMILL SM45 with IC808 inserts at Vc = 250 m/min and fz = 0.25 mm/tooth achieves an MRR of approximately 510 cm3/min with 8 teeth. The CoroMill 345 in the same diameter with GC4235 inserts at Vc = 280 m/min and fz = 0.25 mm/tooth with 10 teeth achieves approximately 640 cm3/min. The Sandvik advantage comes from the ability to fit more teeth in the same cutter diameter due to the smaller insert size and closer tooth spacing.

However, in roughing applications on steel forgings with heavy scale, Iscar’s IC908 grade demonstrates superior resistance to edge chipping compared to Sandvik’s GC4235. The SUMOTEC post-treatment’s compressive stress layer absorbs the impact energy from scale breakout events, reducing unplanned tool changes and maintaining consistent surface quality across the workpiece.

Surface Finish Capability

Surface finish in face milling is influenced by insert geometry, wiper flat length, feed per tooth, and cutting speed. Both systems offer wiper inserts for achieving fine surface finishes in a single pass. Sandvik’s CoroMill 345 wiper geometry achieves Ra 0.8-1.2 um on 42CrMo4 at feed rates up to 0.35 mm/tooth when used with one wiper insert per four standard inserts. Iscar’s SUMOMILL wiper insert achieves Ra 1.0-1.6 um under similar conditions, with a slightly more conservative feed limit of 0.28 mm/tooth for the best finish.

For applications demanding Ra below 0.8 um, Sandvik’s dedicated CoroMill 365 face finishing cutter with precision-ground wiper inserts and GC4205 grade is the superior choice, achieving Ra 0.4-0.8 um on alloy steel surfaces. Iscar does not offer a directly comparable dedicated finishing face mill, relying instead on the SUMOMILL with wiper inserts and reduced feed rates.

Cost per Edge Economics

The CoroMill 345’s 12-edge insert delivers a significant cost-per-edge advantage in high-volume face milling. When machining 1000 engine block deck surfaces per week, the difference between 8 and 12 edges per insert translates to approximately 33% fewer insert changes and correspondingly lower insert consumption. For smaller shops running 10-50 parts per batch, the Iscar SUMOMILL’s 8-edge insert provides sufficient edge count while offering competitive pricing per insert and broader grade compatibility.

Budget Face Milling Alternatives

For operations where premium face milling cutters are not justified, Korloy’s SEKN1203 and SNEX1204 inserts in NC5305 grade provide compatible solutions for standard ISO cutter bodies. These inserts cover general-purpose face milling of steel at speeds of 150-280 m/min and are priced 40-50% below equivalent Sandvik or Iscar inserts, making them suitable for non-critical facing operations on structural steel and mild steel components.

When to Choose Which

Choose Iscar SUMOTEC when you need robust face milling performance in interrupted and scaled surfaces, when insert toughness is more important than absolute edge count, or when you want a versatile cutter that handles both steel and cast iron effectively with the IC808 grade. Iscar’s pricing also tends to be more competitive for small-to-medium batch operations.

Choose Sandvik CoroMill when you face-mill in high volume and need the lowest cost per edge through the 12-edge insert design, when surface finish requirements demand dedicated finishing cutters, or when your operation benefits from the wider cutter diameter range up to 315 mm. The CoroMill 345’s integration with Sandvik’s CoroPlus digital platform also enables automated tool-life management in Industry 4.0 environments.

Conclusion

Both Iscar SUMOTEC and Sandvik CoroMill deliver excellent face milling performance, with Iscar excelling in tough interrupted-cut conditions and Sandvik leading in high-volume production efficiency and surface finish capability. The right choice depends on your production volume, surface finish requirements, and material conditions. Both cutter systems, along with budget-compatible alternatives from Korloy, are available through hooguu.com, your single source for premium and value carbide milling solutions.