Cleveland C42691 Square End Mill 5/16 in 4 Flute Cobalt

Product Description

The CLEVELAND C42691 is a 4-flute cobalt square end mill designed for high-performance milling in demanding materials. Built from M42 cobalt high-speed steel, this end mill handles high-temperature alloys, stainless steel, and carbon steel where standard HSS tooling falls short. The cutting diameter is 0.3125 inches (5/16 inch) with a 0.75-inch length of cut and a 0.375-inch straight-cylindrical shank compatible with standard end mill holders and Weldon flat retention. A 30-degree helix angle and spiral flute geometry promote chip evacuation and reduce cutting forces across a range of milling operations.

The C42691 belongs to the HGC-4C series and is suited for peripheral milling, slotting, and profiling applications in job shop, toolroom, and production environments. The centercutting geometry allows plunge entry, expanding its utility on vertical machining centers and knee mills. Primary target materials include high-temperature alloys (ISO S), stainless steels (ISO M), and steels (ISO P), making it a go-to selection when workpiece hardness or work-hardening tendency demands a more wear-resistant tool material than standard M2 HSS.

Key Features

• M42 cobalt construction for increased red hardness and wear resistance over standard HSS
• 4 flutes with 30-degree right-hand spiral for efficient chip evacuation
• Centercutting design enables direct plunge milling without a pre-drilled entry hole
• Straight-cylindrical shank with Weldon flat for positive rotational drive in end mill holders
• Regular-length profile (2.5-inch OAL) for rigidity and reduced deflection in shoulder and slot milling
• Uncoated finish — suitable for re-sharpening and compatible with oil-based cutting fluids

Compatibility

Designed for use in standard 3/8-inch end mill holders, collet chucks, and Weldon-style set-screw holders on vertical machining centers, knee mills, and CNC machining centers. Primary workpiece materials are high-temperature alloys, stainless steel, and steel.

Installation Notes

Installation and tool changes should be performed by a qualified machinist with the spindle fully stopped and machine power isolated per shop lockout/tagout procedures. Seat the shank fully into the holder and verify Weldon flat alignment before tightening set screws to the holder manufacturer specification. Inspect the cutting edges for chips or wear before each use — a damaged cobalt end mill should be removed from service or sent for re-sharpening rather than run to failure. Use an appropriate cutting fluid or coolant for the workpiece material to maximize tool life.