Sandvik Coromant 7861125 Turning Insert VBMT331-UM 4425

Product Description

The SANDVIK COROMANT 7861125 is a VBMT-style indexable turning insert from the CoroTurn 107 series, ground from carbide stock and finished with a CVD-applied multilayer coating of Al2O3, TiN, and TiCN under manufacturer grade 4425. The insert features a 35-degree diamond shape (V-code), a 3/8-inch inscribed circle, and a 0.40 mm corner radius with the UM chip breaker geometry. Neutral hand orientation means it mounts without left or right restriction. The combination of hard substrate and CVD coating targets general turning of steel and cast iron at production feed rates. Licensed machinists and CNC lathe operators are the primary installers.

This insert is designed for external and internal turning applications on CNC and manual lathes where a positive-rake, sharp-edged diamond insert geometry delivers clean chip control. Primary workpiece material is steel (ISO material group P); secondary workpiece material is cast iron (ISO material group K). The UM chip breaker geometry suits light-to-medium depth-of-cut finishing and semi-finishing passes. Two cutting edges are available per insert, and the insert is held by clamp or screw depending on the toolholder configuration used.

Key Features

• CVD multilayer coating: Al2O3, TiN, and TiCN for wear resistance and thermal stability on steel and cast iron
• 35-degree diamond insert shape (V) with 5-degree relief angle (B clearance code) for positive cutting geometry
• 3/8-inch (0.3750 inch) inscribed circle with 0.40 mm corner radius and UM chip breaker
• Neutral hand orientation — compatible with both right-hand and left-hand toolholder setups
• Two usable cutting edges per insert, extending service life per unit
• Tolerance code M, ISO designation VBMT 16 04 04-UM 4425 for cross-reference to ISO toolholder systems

Compatibility

Designed for use with CoroTurn 107 series toolholders that accept VBMT-style inserts with a 0.1732-inch hole diameter and clamp or screw holding method. ISO code VBMT 16 04 04-UM 4425 may be used to cross-reference compatible toolholder systems.

Installation Notes

Installation is performed by a qualified machinist or CNC tooling technician. Power down and lock out the machine spindle before changing inserts. Seat the insert fully against the toolholder pocket surfaces before tightening the clamp or screw; an improperly seated insert can fracture under cutting loads. Inspect the pocket and clamp for wear or debris before each insert index.