Product Detail
Ball Nose End Mill
Carbide ball nose end mills for steel 3D surfaces and concave fillets, with the ball radius sized to the smallest radius on your model.
The cavity comes off the machine with cusp lines you can see and feel, and the finish is worst on the flattest areas.
A ball nose end mill has a half-sphere tip, so it can follow 3D surfaces and run into concave fillets. The finish it leaves comes down to three things: the ball radius, the step-over between passes, and which part of the ball is actually cutting.
HENTRY grinds end mills as a supporting line next to our drills and reamers.
Choosing the ball radius
Start from the smallest concave radius on the model. A ball larger than that cannot reach the bottom of the fillet and leaves material behind. Below that limit, bigger is better: a larger ball leaves smaller cusps at the same step-over and is stiffer, so it holds its path better. The usual plan is the largest ball the model allows for the main surfaces, with a smaller one only for the rest areas it could not reach. Deep cavities may need a long-neck ball, ground to your drawing.
Step-over, scallops and finish
Each pass of a ball leaves a small ridge, or scallop, between itself and the pass before. The scallop grows quickly as the step-over widens and shrinks as the ball gets larger, so the programmer trades cycle time against finish. Set the step-over from the finish the drawing asks for. Scallop height is pure geometry; the surface roughness you measure also depends on runout, tool wear and the machine.
Why the tip finishes badly
At the very center of the ball the cutting speed is zero, because that point does not travel around the axis. On near-flat areas the tool cuts close to that center, so it rubs more than it cuts and the finish suffers. At a shallow depth the ball also cuts on a smaller effective diameter than its nominal size, so work out spindle speed from that working diameter, not from the size on the label. Tilting the tool or the part moves the cut away from the center, which is the usual fix on five-axis machines. For nearly flat floors that end in a fillet, a corner radius end mill often does the job in fewer passes.
Ball nose, corner radius or square
Freeform 3D surfaces and full concave fillets call for a ball nose. A flat floor with a drawn fillet, or a gently sloping surface, usually goes faster with a corner radius tool, while a flat floor with a sharp corner needs a square end mill. For 3D contours in abrasive, high-silicon aluminum, use a PCD ball nose end mill instead.
Ball nose RFQ: the inputs that size the tool
The model's smallest radius matters most; the rest sets reach and finish.
- Material, and its hardness after heat treatment
- The smallest concave radius on the model, or the CAD or STEP file
- Ball diameter if you have already picked one, and the reach or neck the cavity needs
- Surface finish target from the drawing
- Your plan for roughing, semi-finishing and finishing
- Three-axis, or five-axis with the tool tilted
- Machine model and toolholder type
- The trouble today: cusp marks, tip wear or chatter
- Number of tools
Flute count and coating each have their own page: 4-flute carbide end mill and AlTiN coated end mill. For the mold and die process as a whole, read our page on die and mold contours.
The standard end mill types are on our carbide end mills page, and long-neck or other non-standard ball tools are on our custom end mill manufacturer page. Send the model's smallest radius and the material through the custom cutting tool RFQ, and we propose a ball size and reach for your approval.
Solid carbide ball nose end mill FAQ
What size ball nose end mill do I need?
The largest one whose radius still fits the smallest concave radius on your model. Use a smaller ball only for the rest areas the main tool cannot reach.
Why does a ball nose end mill leave a poor finish on flat areas?
On flat areas the cut runs near the center of the ball, where cutting speed is zero, so the tool rubs. Tilting the tool or the part helps, or a corner radius tool can take the flat areas.
How do I reduce scallop marks with a ball nose end mill?
Use a smaller step-over, a larger ball where the model allows it, or both. Set the target from the finish on the drawing, and check runout too, since it also shows in the finish.
Can you make a long-reach ball nose end mill for deep cavities?
Yes. Long-neck ball nose end mills are among the special forms we grind to your drawing; send the cavity depth and smallest radius with your RFQ.