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.
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
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
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
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.