Ball Nose vs Tapered Ball Nose: Bits for CNC 3D Carving

3D carving is where a CNC stops cutting shapes and starts making surfaces: reliefs, signs with depth, bowls, moulds and models. The bit that does it has a round end. Choosing one comes down to ball nose or tapered ball nose, what radius, and which material. For roughing and stepover basics, also read our feeds and speeds guide.

Rough with a flat, finish with a ball

Most 3D jobs use two tools. First, a flat end mill (an up cut or compression bit) clears the bulk in steps and leaves a little material on. Then a ball nose follows the surface with a small stepover and leaves a smooth finish. A flat bit alone leaves terraces, and a ball nose alone takes far too long to remove bulk.

Ball nose vs tapered ball nose

• Ball nose: the radius is half the diameter, with no flat bottom. It's the budget-friendly 3D bit for wood and plastics, from R1 to R6. Use the bigger radii for large, smooth reliefs. They also engrave text.
• Tapered ball nose: a small ball tip (R0.25–R2) on a tapered body. The taper makes a tiny tip strong enough for fine detail and deep walls. It's the most versatile bit in a 3D set, and also does PCB tracks and engraving in plastic, aluminium, brass and steel.

The tapered ball nose comes in different angles depending on size, so choose by tip radius for the detail you need and by length for how deep the carving goes.

Choosing the radius

• R0.25–R0.5: fine detail such as faces, feathers and small lettering. These need a small stepover and long run times.
• R1–R1.6: the general relief carving range.
• R3 and up: large, smooth surfaces such as bowls, dished signs and big reliefs, where you want a fast finish pass.

A smaller radius picks up more detail but needs a smaller stepover to look smooth, so it takes longer. Pick the largest radius that still fits the finest detail in your model.

Which material

• Timber, MDF, plastics: the ball nose for 3D carving or the tapered ball nose.
• Aluminium, brass, copper: the DLC ball nose, whose coating stops chips welding on, or the uncoated HRC45 ball nose with the sharpest edge.
• Steel, stainless, mould work up to HRC55: the TiSiN ball nose.
• Thick XPS / EPS foam blocks: the extra-long HSS ball nose, with up to 300mm overall length, for deep foam carving and moulds.

For flat-floored trays, boards and raised-letter backgrounds, a bowl and tray bit is faster than a ball nose and leaves a clean radius into the wall.

Adam's Tip

In timber, cut across the grain to reduce fuzz in the carve. Set this with the raster angle in your 3D carving software. Take light depths of cut with the tapered ball nose and make up the time with feed rate.

Frequently asked questions

What is the best bit for 3D carving on a CNC router?

A tapered ball nose for fine detail, or a standard ball nose for larger, smoother reliefs. Rough out first with a flat end mill, then finish with the ball nose.

What is the difference between a ball nose and a tapered ball nose?

A ball nose has a radius equal to half its diameter and straight sides. A tapered ball nose has a small ball tip on a tapered body, which keeps a very fine tip strong and lets it reach down deeper walls.

What size ball nose should I use?

Pick the largest radius that still fits the finest detail in your model. R0.25–R0.5 for fine detail, R1–R1.6 for general relief carving, and R3 or larger for big smooth surfaces.

Can I 3D carve aluminium with a ball nose?

Yes. Use a DLC or uncoated ball nose ground for non-ferrous metals, with coolant or an air blast, and take light depths of cut.