End Mill Geometry Explained (Square End vs Ball Nose vs Corner Radius)

End Mill Geometry Explained

End mill geometry refers to the shape of the cutting end. Geometry affects how a tool enters the material, the surfaces it can create, and the type of finish produced.

This guide explains the practical differences between Square End, Ball Nose, and Corner Radius end mills so you can choose quickly using filters on our collection pages.

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Square End

What it is

• Flat-bottom cutting end with sharp corners
• Produces flat floors and crisp inside corners (limited by tool diameter)

Best used for

• Slotting and pocketing
• Flat-bottom features
• General-purpose milling

Considerations

• Sharp corners are more prone to chipping in brittle materials

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Ball Nose

What it is

• Rounded cutting end (hemispherical)
• Designed for smooth contouring and 3D surfaces

Best used for

• 3D carving and contouring
• Curved or sloped surfaces
• Finishing passes where surface smoothness matters

Considerations

• Not ideal for perfectly flat-bottom pockets
• Leaves a radius at the bottom of features

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Corner Radius

What it is

• Flat-bottom tool with a small radius at the corners
• Stronger cutting edge than a sharp-corner square end

Best used for

• Applications where durability is important
• Reducing corner chipping in hard or brittle materials
• Situations where a small internal radius is acceptable

Considerations

• Will not create a perfectly sharp inside corner

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Quick Comparison

Feature	Square End	Ball Nose	Corner Radius
Bottom Shape	Flat	Rounded	Flat with radius
Best For	Slots, pockets, general milling	3D contouring, curved surfaces	Edge strength, reduced chipping
Inside Corner Sharpness	Sharpest possible*	Rounded	Rounded (small radius)
Edge Strength	Good	Good	Best

*Inside corner sharpness is always limited by tool diameter.

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Browse by Geometry

Square End Mills

Ball Nose End Mills

Corner Radius End Mills

Back to All End Mills

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Related Guides

2-Flute vs 3+ Flute — when to use each

Up-Cut vs Down-Cut — cutting direction explained