Ball Nose End Mill: Precision Machining

What is a ball nose end mill?

RNK's ball nose end mill, also known as a "ball mill" or "R-cutter",  is a type of end mill where the tip is ground into a hemispherical shape. Ball nose end mills are always center-cutting, meaning they can cut at any position of the ball. They can be single-edged or double-edged. They can be made from solid carbide or high-speed steel and can be coated. Depending on the material being processed, they offer various groove options. They are used for milling large fillet radii, slotting, and contour milling. Smaller diameters can be used for engraving. Their primary applications are 3D semi-finish and finish operations in industries such as mold making. Additionally, there are tapered ball nose end mills and indexable ball nose end mills.

Issues in milling with ball nose end mills

The milling process with ball nose end mills is prone to leaving residues, such as the red areas in the above image. The size of these residues depends on the diameter of the ball end, cutting depth, and the step-over distance between continuous cuts. The height of the residue increases with the milling step-over distance, so it's crucial to use the smallest possible step-over distance when using ball nose end mills to reduce residue height.

Feed and speed of ball nose end mills

Calculating the Effective Diameter of the Tool

Effective Diameter = 2 x SQRT (Cutting Depth x (Diameter – Cutting Depth))

The above formula is only applicable when the cutting depth is less than the radius of the ball nose end mill.

After calculating the effective processing diameter, refer to the corresponding milling parameters

Notes

Tool Installation

Ensure the tool is securely installed to prevent loosening or falling off during the cutting process.

Cutting Parameters

Select appropriate cutting speed, feed rate, and cutting depth parameters based on the material being processed and the characteristics of the tool to ensure processing quality and tool life.

Maintenance

Regularly inspect and maintain the tool, such as cleaning chips off the cutting edge and checking for tool wear, to extend tool life and improve processing efficiency.