Corner Radius End Mill Blending

Good & Bad Radius Blends

Carbide End Mills come in many shapes and sizes, in this article we are discussing a Corner Radius Carbide End Mill. There are several reasons why a corner radius end mill would be the tool of choice; but the most common is for tool strength. A radius can prevent corners from chipping or breaking down. The corner on an End Mill is the weakest part of the tool. Another common reason for using a radius end mill is that it is a finish part specification or requirement. A radius can come in various sizes depending upon the cutting diameter.

One of the most common problems you can see in the marketplace is poor blending of corner radius end mills; meaning that the radius in not tangent or more commonly referred to as an “undercut” or “step”.

It is critical that a radius blends perfectly because any imperfection will be transferred directly to the part. This could result in many problems including poor finish, or leaving a line / ridge in the part itself. For this reason, we don’t recommend adding a radius to a finished end mill. It’s always best to have the end mill manufactured with the desired radius.

Below are photos of what you do and don’t want to see when purchasing a Corner Radius Carbide End Mill.

Carbide End Mill—Proper Blend
Shown: 1/4″ 4FL with .020 Corner Radius

Close up:
End Mill Corner Radius shown with proper blend

Corner Radius—Poor Blend
End (Top) of the End Mill

Corner Radius—Poor Blend
OD (outside diameter) or side of the End Mill

If need an end mill manufacturer that will ensure exact geometry every single time, than look no further than Advanced Tool Inc. We’d love to help you with your next end milling project.