How to Choose Corner Radius End Mills: A Complete 2026 Selection Guide

August 12, 2026 · Exactalloy Technical Team

Choosing the wrong corner radius end mills costs more in scrap, tool changes and cycle time than the tool itself. This guide walks through the six decisions that determine performance.

Quick answer: Match the tool to (1) workpiece material and hardness, (2) operation type, (3) machine capability and coolant, then (4) pick substrate, (5) coating and (6) geometry. Exactalloy stocks corner radius end mills from HRC 45–65 across 6 standard lines.

Step 1 — Identify the workpiece material and hardness

Alloy steel, pre-hardened steel, stainless steel, cast iron. Hardness above HRC 45 usually rules out standard grades and pushes you to TiAlN, AlTiN, AlCrN.

Step 2 — Match tool geometry to the operation

Available geometries: R0.2–R6.0 corner radius, 4-flute. Choose the shortest flute length and largest core diameter that reaches the feature.

Step 3 — Select substrate and coating

Typical coatings for this family are TiAlN, AlTiN, AlCrN. Coating choice trades wear resistance against edge sharpness and cost.

Step 4 — Set cutting parameters

Start from the manufacturer surface speed, then adjust feed per tooth until chip formation is correct. Rigid set-ups tolerate higher feeds.

Step 5 — Verify run-out and coolant

Run-out above 0.01 mm shortens tool life sharply; measure at the cutting edge, not the shank. Through-coolant extends life in deep pockets.

Specifications at a glance

Decision	What to check	Typical answer
Material	Hardness, ISO group	alloy steel
Geometry	Operation, reach	R0.2–R6.0 corner radius
Coating	Abrasion vs adhesion	TiAlN
Coolant	Depth, chip evacuation	Through-coolant for depth > 2×D

Frequently asked questions

What hardness can these tools handle?

This family typically covers HRC 45–65, verified by the substrate grade and coating.

Can I use one tool for roughing and finishing?

Not optimally — roughing geometries trade edge sharpness for strength, so finishing needs a separate tool.

Do I need through-coolant?

Required for holes or pockets deeper than twice the diameter, or where chips cannot escape.

Get a quote and technical support

Exactalloy supplies corner radius end mills from stock, made-to-order and reground. Send your drawing or specification for a quotation and lead time within 24 hours. Contact us or browse all products.