The right cutter decides whether your CNC project succeeds or fails. But the choice is huge: solid carbide, HSS, coated, single-flute, multi-flute. What do you really need? This guide helps you choose tools for different materials.
Basics: Understanding Cutter Types
End Mills
The all-rounder among cutters. It cuts with the end face and the flanks:
- Flat end mill: flat bottom, sharp corners, for pockets and contours
- Bull nose end mill: rounded corners, more stable, less corner wear
- Ball nose end mill: hemispherical, for 3D surfaces and finishing
Helical End Mills
End mills with helical cutting edges, decisive for chip evacuation:
- Upcut (right-hand helix): chips go upwards, good evacuation, the top edge may tear out
- Downcut (left-hand helix): chips go downwards, clean top edge, chips stay in the cut
- Compression: combines both, with clean edges at the top and bottom
V-Groove Cutters
Conical cutters with a pointed tip for engraving and V-carving:
- Point angles of 30°, 60° and 90° are common
- The more pointed, the finer the details
- The blunter, the more stable
Drills and Special Tools
- Centre drill: for spotting before drilling
- Step drill: several diameters in one tool
- Tap: for cutting threads. The thread feed calculator gives you the matching feed rate.
- Chamfer cutter: for breaking edges
Tool Materials
HSS (High-Speed Steel)
- Advantages: inexpensive, tough, easy to resharpen
- Disadvantages: shorter tool life, not for hard materials
- Suitable for: wood, soft plastics, aluminium at low spindle speeds
Solid Carbide
- Advantages: high hardness, long tool life, high spindle speeds possible
- Disadvantages: brittle (breaks when overloaded), more expensive
- Suitable for: all materials, the standard for CNC machining
Coatings
- TiN (titanium nitride): gold, general improvement
- TiAlN: violet/grey, good for dry machining
- DLC (diamond-like carbon): black, excellent for aluminium and plastic
- Uncoated: often sufficient for wood and plastic
Number of Flutes: Sometimes Less Is More
| Flutes | Advantages | Disadvantages | Ideal for |
|---|---|---|---|
| 1 (single-flute) | Maximum chip evacuation, no clogging | Lower feed rates | Plastic, aluminium, deep slots |
| 2 | Good balance of evacuation and feed rate | - | Wood, plastic, aluminium |
| 3 | Higher feed rates, smoother surfaces | More heat, risk of clogging | Aluminium, harder materials |
| 4+ | Highest feed rates, best surfaces | Small chips only, clogs in wood | Steel, hard machining |
Rule of thumb: the softer the material and the longer its chips, the fewer flutes.
Choosing Cutters by Material
Wood and MDF
Recommended cutters:
- Solid carbide helical end mills with 1–2 flutes
- Upcut for pockets and deep cuts
- Downcut or compression for clean surfaces
- V-groove cutters for engraving
Special features:
- Wood is fibrous, so the cutting direction matters
- MDF is abrasive: solid carbide recommended
- With hardwood: slightly lower spindle speeds, otherwise there is a risk of burning
Plastics
Recommended cutters:
- Solid carbide single-flute cutters with a polished flute (O-flute)
- Large chip space for good evacuation
- Sharp cutting edges
Special features:
- PMMA (acrylic): high spindle speed and high feed rate, otherwise it melts
- POM: very forgiving
- PA (nylon): tough, high feed rates needed
- PE/PP: very soft, extremely sharp tools
Aluminium
Recommended cutters:
- Solid carbide with 1–3 flutes
- Polished flutes (against built-up edge)
- DLC or ZrN coating ideal
- Large rake angles
Special features:
- Aluminium sticks, so cooling and lubrication are important
- Single-flute cutters for deep slots
- Three-flute cutters for high feed rates when finishing
Brass and Bronze
Recommended cutters:
- Solid carbide with 2–3 flutes
- Uncoated or with TiN coating
Special features:
- Usually easy to machine
- Some alloys produce long chips
Steel
Recommended cutters:
- Solid carbide with 4+ flutes
- TiAlN coating for dry machining
- Cooling recommended
Special features:
- Requires a rigid machine
- Low spindle speeds, moderate feed rates
- Not for hobby machines
Choosing the Tool Diameter
The diameter affects several factors:
| Diameter | Advantages | Disadvantages | Typical application |
|---|---|---|---|
| 1–2 mm | Fine details, small radii | Very prone to breakage | Engraving, PCBs |
| 3–4 mm | Good compromise | - | Details, small parts |
| 6 mm | Standard, good stability | - | All-round machining |
| 8–10 mm | High removal rate | Larger radii | Roughing, large parts |
| 12+ mm | Maximum productivity | Large radii, more power needed | Industrial production |
Rule of thumb: as large as possible, as small as necessary. Smaller cutters for details, larger ones for volume.
The Basic Set for Beginners
With these cutters you cover most applications:
- Solid carbide end mill 6 mm, 2-flute: your main tool
- Solid carbide end mill 3 mm, 2-flute: for details and small radii
- Solid carbide single-flute cutter 6 mm: for plastic and deep pockets
- V-groove cutter 60°: for engraving and V-carving
- Ball nose end mill 6 mm: for 3D surfaces
It is better to invest in a few good cutters than in many cheap ones. Quality tools last longer and deliver better results.
We stock all the tool types mentioned here (solid carbide end mills, single-flute cutters, V-groove cutters, ball nose end mills and drills) in the Milling tools category. Also recommended for aluminium and metal: Lubrication & cooling.
Extending Tool Life: Tips
- Correct parameters: running too slowly is often more harmful than running too fast
- Cooling/lubrication: almost always sensible for aluminium and metal
- Remove chips: good dust extraction or compressed air
- Do not cut too deep: better to make several passes
- Ramp up at changes of direction: reduces edge wear
FAQ: Frequently Asked Questions
Solid carbide or HSS: which is better?
For CNC machining, almost always solid carbide. HSS is cheaper, but the shorter tool life and lower cutting speeds make solid carbide more economical. Use HSS only for very large diameters or when the risk of breakage is high.
How do I recognise a blunt cutter?
Signs: poorer surfaces, more heat, higher motor current, squealing noises, discolouration on the tool or workpiece. If in doubt, change it.
Can I use wood cutters for aluminium?
In theory yes, but in practice it is not recommended. Aluminium cutters have different geometries (rake angle, polished flutes) that prevent built-up edge. With wood cutters, the aluminium sticks.
How many cutters do I need?
Four to five different cutters are enough to start with. Buy more as you need them. Better one good cutter than ten cheap ones.
Conclusion: Quality Pays Off
The cutter is the direct contact between machine and material. A good cutter with the right parameters delivers excellent results. A poor cutter struggles even on the best machine.
Our recommendation: start with a small selection of high-quality solid carbide cutters. Expand it as needed for specific applications.
Related Guides
Do you need advice on tool selection? Contact us and we will be glad to help you choose for your application.
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