Cleveland C42857 Square End Mill 3/8 in 4 Flute Cobalt

Product Description

The CLEVELAND C42857 is a cobalt square end mill designed for high-performance milling in demanding metal-cutting applications. Built from M42 cobalt high-speed steel, this 4-flute, single-end tool features a 0.375-inch cutting diameter, a 1.5-inch length of cut, and a 3.25-inch overall length. The spiral flute geometry and 30-degree helix angle promote efficient chip evacuation and smooth cutting action. Centercutting capability allows for direct plunge entry into workpiece material. The uncoated finish makes it suitable for applications where coating compatibility or regrinding costs are a concern. Licensed machinists and tool-and-die professionals are the primary users of this end mill.

The C42857 is intended for milling high-temperature alloys, stainless steel, and carbon and alloy steels. These are among the most demanding workpiece materials in machining, and the M42 cobalt grade is selected specifically for its red hardness and wear resistance at elevated cutting temperatures. Typical install scenarios include CNC milling centers and manual knee mills in job shops, aerospace shops, and general precision machining environments. The straight cylindrical shank with Weldon flat accommodates standard side-lock tool holders for positive drive and minimal runout.

Key Features

• M42 cobalt construction for increased hardness and heat resistance compared to standard HSS
• 4-flute spiral geometry with 30-degree helix angle for efficient chip removal
• Centercutting design allows direct plunge milling without pre-drilling
• Long series length of cut (1.5 inches) for deeper slot and peripheral milling operations
• Right-hand cut, right-hand flute configuration — standard orientation for conventional and climb milling
• Straight cylindrical shank with Weldon flat for positive retention in side-lock holders
• Uncoated finish supports straightforward regrinding and broad coolant compatibility

Compatibility

The C42857 belongs to the Cleveland HGC-4C series and is designed for use in standard 3/8-inch end mill holders, collet chucks, and Weldon-style side-lock tool holders. It is suited for milling high-temperature alloys, stainless steel, and steel workpiece materials as indicated by ISO material codes M, P, and S.

Installation Notes

Installation is performed by qualified machinists or tooling technicians. The machine spindle must be fully stopped and the tool changer or quill locked before inserting or removing end mills from any holder. Ensure the Weldon flat is properly aligned with the setscrew in the holder to prevent axial pullout under load. Verify runout at the tool tip with a dial indicator before cutting; excessive runout accelerates flute wear and reduces surface finish quality.