When you move from simple 2D slots and pockets to complex 3D contours, your tool selection becomes critical. The two most important tools in the 3D machining playbook are the Ball Nose end mill and the Corner Radius end mill. While they may look similar, they serve very different purposes.
1. The King of 3D: The Ball Nose End Mill
What is it?
A Ball Nose end mill has a cutting edge with a full, perfectly round radius (equal to half the tool's diameter). It has no flat bottom.
When to Use It:
This is your go-to tool for true 3D surfacing.
Complex Contouring: Ideal for machining organic shapes, complex molds, and any surface with flowing, non-flat geometry.
3D Finishing: When paired with a small "stepover" in your CAM program, the ball nose can produce a smooth, scalloped-free surface finish.
Surfacing with "Z-Level" or "Parallel" Toolpaths: These are the tools that CAM finishing strategies are designed for.
Limitation: It is terrible at creating flat floors. Since the center of the tool is on a perfect radius, it cannot produce a truly flat surface.
2. The Versatile Workhorse: The Corner Radius (Bull Nose) End Mill
What is it?
A Corner Radius (or Bull Nose) end mill is a flat-bottom end mill, but with its sharp, 90-degree corners replaced by a small, specific radius (e.g., 0.5mm, 1mm).
When to Use It:
This tool is all about adding strength and versatility.
Adding Strength: The sharp, 90-degree corner of a standard square end mill is its weakest point and most likely to chip. Adding a radius makes the tool dramatically more durable, allowing for higher feed rates and longer tool life, especially in tough materials.
Pocketing with a Floor Radius: Most 2.5D parts (like a pocket) don't require a perfectly sharp corner at the bottom. A corner radius end mill can machine the flat floor and the curved transition to the wall in a single pass.
"Z-Level" Roughing: It's an excellent choice for roughing out 3D shapes, as it leaves a more consistent, terraced shape for the finishing tool to clean up.
Conclusion: Which One Do You Need?
If you are machining 3D, sloping, organic surfaces (like a mold cavity or an artistic model): You need a Ball Nose End Mill for the finishing pass.
If you are machining 2.5D pockets and want a stronger, longer-lasting tool for profiling or floor finishing: You need a Corner Radius End Mill.
Many advanced CAM strategies use both: a Corner Radius end mill for roughing and semi-finishing, followed by a Ball Nose end mill for the final, precise 3D finishing pass.
Upgrade your 3D machining. Shop our precision-ground Ball Nose and Corner Radius end mills to achieve the perfect finish.
