Views: 177 Author: Site Editor Publish Time: 2025-12-21 Origin: Site
Choosing the right CNC bits doesn’t have to be overwhelming—even for beginners. The key is to focus on core factors like your workpiece material, machining type, and basic tool specs. This guide breaks down the process step by step, with simple explanations and practical tips to help you avoid common mistakes.
The material you’re cutting dictates 80% of your tool choice. Different materials have unique hardness and cutting needs, so match your CNC router machine bit to the job:
Soft Materials (Aluminum, Plastic, Wood)
Recommended bits: High-Speed Steel (HSS) or coated carbide bits. HSS offers good toughness and affordability for hobby projects, while carbide bits with diamond coating reduce material sticking.
Avoid: Brittle ceramic or CBN bits—they’ll chip easily on low-hardness materials.
Medium-Hard Materials (Steel, Stainless Steel, Cast Iron)
Recommended bits: Carbide bits (standard or TiAlN-coated). Carbide’s high hardness and wear resistance handle steel’s toughness, while TiAlN coating boosts heat resistance for longer life.
For stainless steel (sticky and tough): Choose carbide bits with sharp edges and anti-chip coatings to prevent built-up edges.
CNC work involves different operations, and each needs a special bit shape:
Milling (Flat Surfaces, Slots, Edges)
Flat end mills: For straight slots and flat surfaces (choose 4-flute for metal, 2-flute for wood/plastic to reduce clogging).
Ball end mills: For curved surfaces or 3D carving (leaves a smooth finish, great for hobby crafts).
Roughing end mills: For fast material removal (serrated edges break chips easily, saving time on large projects).
Drilling (Holes)
Twist drills: Standard for most holes—carbide-tipped for metal, HSS for wood/plastic.
For deep holes: Choose bits with internal coolant holes (reduces heat and prevents tool breakage, critical for steel or titanium).
Threading (Tapping Holes)
Spiral taps: Best for metal—use powder metallurgy HSS for steel, carbide taps for hard materials.
For high-hardness steel (HRC 50+): Skip taps entirely—use carbide thread mills for better results.
You don’t need to master all technical details, but these three specs matter:
Coating
TiAlN (Titanium Aluminum Nitride): Most versatile—handles steel, stainless steel, and high temperatures (up to 1000°C).
Diamond Coating: Perfect for aluminum and non-metals (reduces friction and sticking).
Uncoated: Budget option for low-speed cutting of soft materials.
Flute Count
2-flute: Better for wood/plastic (wider chip slots prevent clogging).
4-flute: Ideal for metal (more cutting edges = smoother cuts and faster speed).
6+ flutes: For precision finishing (reduces vibration, great for detailed metal parts).
Shank Size
Match the bit’s shank (the non-cutting part) to your CNC machine’s collet. Common sizes are 1/4" (6mm) and 1/2" (12mm)—a loose fit causes vibration and poor precision.
Start with affordable bits: HSS or basic carbide bits are great for practice—no need to splurge on premium tools until you master the basics.
Check cutting parameters: Even the right bit fails if you run it too fast. For example, aluminum needs higher speed but lower feed rate than steel.
Avoid overworking the bit: Don’t cut too deep in one pass—shallow passes reduce heat and extend tool life.
Clean bits regularly: Built-up material (especially on aluminum or plastic) dulls edges—wipe bits with a solvent after use.
The key factors include material to be cut (wood, metal, acrylic, etc.), cutting operation (carving, engraving, profiling, drilling), router bit material (carbide, high-speed steel, diamond-tipped), flute design (up-cut, down-cut, compression), and compatibility with your CNC machine’s spindle speed and collet size.
Up-cut bits: Push chips upward, ideal for deep cuts and roughing; may cause slight top surface splintering.
Down-cut bits: Pull chips downward, produce clean top surfaces; suitable for finishing and thin materials.
Compression bits: Combine up-cut and down-cut flutes, minimize splintering on both top and bottom surfaces; perfect for plywood and laminated materials.
It is not recommended. Different materials require specific bit materials and geometries. For example, carbide-tipped bits work well for wood and soft metals, while diamond-tipped bits are needed for hard materials like stone or glass. Using the wrong bit will reduce tool life and cut quality.
Each router bit has an optimal spindle speed range, which is related to its diameter and material. Smaller bits need higher speeds to achieve sufficient cutting edge velocity, while larger bits require lower speeds to avoid excessive vibration. Mismatched speed can cause poor cuts, tool wear, or even bit breakage.
The shank size must match your CNC machine’s collet size (common sizes: 1/4", 1/2"). Larger shanks (e.g., 1/2") offer better stability and reduce deflection, making them suitable for heavy cutting operations. Smaller shanks (e.g., 1/4") are used for light engraving or detailed work.
Use appropriate cutting speeds and feeds for the target material.
Keep the bit sharp and clean (remove resin or chip buildup regularly).
Avoid overheating by using coolant (for metal cutting) or reducing cutting depth.
Store bits in a dry, organized case to prevent damage or corrosion.
Replace the bit when you notice dull cutting edges (rough cuts, increased cutting force), chip buildup that cannot be removed, visible wear or chipping on the cutting edges, or vibration and noise during operation.
By following these steps, you’ll choose CNC bits that work for your projects, save material waste, and protect your machine.
