Corner Radius End Mills

Specify the Radius as Well as the Diameter

A corner radius end mill, also called a bull nose end mill, has a radiused transition at the cutting edge rather than a sharp square corner. It remains different from a ball nose end mill: the end profile and the part geometry it produces are not the same.

For a distributor or machining supplier, ordering by diameter alone leaves too much room for error. State the corner radius, flute count, cutting length, overall length and shank diameter with each model. Where the catalog gives an effective length, include that dimension as well. This lets your customer compare the requested tool against the drawing and the holder before the order is placed.

• Radiused cutting corners for matching the required part geometry
• 2- and 4-flute options across the listed series
• Select each model by cutter diameter, corner radius and length

Corner Radius End Mill Series

Choose a series first, then check the individual model and dimension drawing. The catalog identifies the following corner radius groups:

The catalog contains 315 model records across these eight groups. ERA and ERB are identified in the catalog as copper-electrode series; select the other groups by their corresponding model record and intended application. Send your model list for a series-specific quotation.

Find the Right Dimensions for Your Order

Use the drawing and specification table together. A tool's cutting diameter does not identify its corner radius, flute length or clamping size. When you prepare an assortment, keep each of the following fields attached to the model code:

• Cutting diameter: the diameter of the cutting section specified for the model.
• Corner radius: the radius at the cutter's outer corner; match it to the feature on the component drawing.
• Flute length: the length of the fluted cutting section.
• Overall length: the tool's total length, including the shank.
• Shank diameter: the dimension to compare with the holder's clamping range.
• Flute count: the number specified for that series.
• Effective length: use this field where it is provided in the catalog; it is not the same as overall length.

A drawing may call for a particular internal corner radius, or it may allow a tool to leave material for a later operation. Confirm the part requirement and toolpath before choosing the radius. Check access and clearance in the actual holder assembly, particularly when working inside a recessed feature.

Where Corner Radius End Mills Fit

A corner radius tool is relevant when the machined shape calls for a transition at the edge of the cutter. The final tool choice still depends on the workpiece, program and clearance.

Shoulders and stepped features. Match the corner radius to the geometry required at the junction between the floor and the wall. If a sharp internal corner is required, compare the drawing with the selected radius before ordering.

Pocket and cavity work. Check the cutting diameter, cutting length and available clearance against the pocket. Distinguish the length of cut from the distance the holder must reach into the feature.

Copper-electrode machining. The ERA and ERB catalog groups are designated for copper electrodes. Compare the relevant model dimensions with the electrode feature and the machine holder; do not extend that designation to other series without their corresponding catalog evidence.

Compare Corner Radius, Square and Ball Nose Profiles

These are different tool profiles, not automatic substitutes. A matching shank or cutting diameter alone does not establish that the finished feature will be the same.

Corner Radius Is Not Corner Rounding

A corner radius end mill has a radius on the outer corner of its cutting end. A corner rounding cutter is a different tool form used to create a rounded outside edge on a workpiece. Send the part drawing or tool profile with your request if the order uses either term; the desired part shape determines which cutter geometry to specify.

Two Flutes or Four?

The catalog includes both two-flute and four-flute corner radius groups. Flute count is one input to a tooling decision: the workpiece, cutter geometry, chip evacuation, machine setup and programmed engagement also matter. Select a listed model that matches the intended operation rather than assuming one flute count is best for every material.

For repeat purchasing, keep the series, flute count, diameter and corner radius together on the order. If a customer is changing from one series to another, compare the complete dimension drawing and the application conditions before approving the replacement.

Production and Quality

Review the tool geometry, model identification and required dimensions against the catalog drawing and agreed order details. For a repeat order, keep the approved model and drawing reference with the purchase record so the same cutting diameter, corner radius, shank and length can be specified again.

Packaging and Order Details

Send the required model codes and quantities per size. If you need a particular label, logo, barcode or packing format, include the artwork and packing instructions with your enquiry so the details can be reviewed for the selected order. Provide any sample or delivery requirements with the request.

Catalog Product Views and Dimension Drawings

Use each series image, dimension drawing and original catalog symbols to compare corner-radius options.

NRB Series · R012

HRA Series · R026

HRB Series · R027

HRBX Series · R030

DRA Series · R048

DRB Series · R051

ERA Series · R065

ERB Series · R066

Catalog Model Specifications

Review the dimensions for each model, including the corner radius where listed. Blank fields and catalog dashes remain unavailable values; they are not converted to zero.

Production Equipment Reference

Explore our workshop equipment and prepare your corner-radius requirements by cutter diameter, radius and flute count.

Inspection and Measurement Equipment Reference

For corner-radius orders, identify the radius, dimensions and edge features specified on your drawing.

Frequently Asked Questions