By the CNC Router UK – Expert Guides, Reviews & Buying Advice Team · Updated May 2026 · Independent, reader-supported

CNC Router Bits Guide UK: Which End Mills Do You Actually Need?

When you're starting with a home CNC router, the bit selection can feel overwhelming. Walk into any supplier's catalogue and you'll find hundreds of options, each claiming to be essential. The truth is simpler: most hobbyists only need three or four types to handle 90% of their work. Understanding what each bit does—and where it actually matters—saves you money and frustration.

Upcut vs Downcut Bits: The Fundamental Choice

Upcut and downcut bits are your workhorses. They're straight-flute bits that remove material vertically, and the difference comes down to chip ejection direction.

Upcut bits pull chips up and out of the cut. This makes them excellent for clearing away debris, which means you can often feed faster and get cleaner cuts in softer materials like MDF, plywood, and hardwoods. The downside: they pull the top surface of your material slightly, creating tearout and a rougher edge. If you're cutting through a laminated sheet and the top layer matters, upcut bits will lift the veneer.

Downcut bits push chips downward. They compress the top surface, giving a visibly cleaner cut on the upper face. This is invaluable when you're cutting veneered plywood or when appearance matters on the show side. The trade-off is that chips pack into the slot, so you need good chip evacuation (slower feeds) or periodic clearing. They're also slightly more aggressive on the router itself.

For typical MDF work and test cuts, an upcut bit is fine. If you're routing decorative edges or cutting plywood where the top surface shows, downcut is worth the extra cost. Many experienced makers keep both and choose based on the job.

Ball-Nose Bits: 3D Contouring and Detailed Work

Ball-nose (hemispherical) bits are worth understanding even if you don't do 3D carving. They're excellent for detailed relief work, decorative edges, and radius cuts that upcut or downcut bits can't produce smoothly.

The rounded tip means the bit cuts gradually rather than dropping straight down, which can reduce chatter and produce a smoother surface finish in hardwoods. If you're carving lettering or creating flowing patterns, a ball-nose cuts more elegantly than a flat-bottomed bit.

The catch: ball-nose bits are slower. The rounded edge moves less aggressively through material than a sharp corner does, so feed rates are lower and cutting time increases. For simple routing tasks, this overhead isn't worth it. But if you're doing detailed work or finishing passes on visible grain, the quality difference is noticeable.

V-Bits: Engraving and Decorative Edges

V-shaped bits come in fixed angles (typically 30°, 45°, or 60°) and are purpose-built for engraving, lettering, and decorative V-grooves. A 45° V-bit is probably most useful for home makers—it creates a balanced, sharp groove that reads well in photographs and doesn't require excessive depth.

V-bits are less forgiving than flat-bottomed bits. If your material isn't perfectly surfaced or your z-zero is slightly off, the groove width and depth change noticeably. Spend time getting your bed flat and your zero accurate before running V-bit jobs. That said, the visual impact is high; V-grooved lettering looks professional and intentional.

The durability is good—the sharp edges eventually dull, but they last longer than you might expect if you're not pushing aggressive feeds.

Compression Bits: Plywood and Laminates

Compression bits combine upcut flutes on the bottom and downcut flutes on the top. They pull chips up but compress both surfaces, giving clean cuts on both edges. These are genuinely useful if you're routing plywood repeatedly or cutting sheet goods where both surfaces matter.

They're more expensive than standard upcut bits and overkill for single-pass cuts in MDF. But if you're doing production work—routing panel edges or cutting laminated assemblies—they save finishing time and reduce sanding. The real advantage appears after 10 or 20 cuts; suddenly you're not spending an hour with sandpaper on both edges of every piece.

What You Actually Need

For a hobbyist or small workshop, start with a basic set: a couple of upcut bits in common diameters (⅛-inch, ¼-inch, ½-inch), one downcut bit for plywood, and one ball-nose for detail work. If you do engraving, add a 45° V-bit. That's genuinely enough to explore what your router can do.

Specialist bits—compression bits, custom angles, multiple sizes—make sense once you've identified your actual workflow. Buying a 12-piece set because it looks comprehensive is how workshops end up with drawers full of dull bits they never use.

Also: invest in good-quality bits rather than budget sets. Cheap bits dull quickly, cut inconsistently, and can deflect under load, producing chatter and poor edges. UK-made or quality German bits tend to hold sharpness longer and cut more reliably. The cost difference is modest on a per-project basis.

Keep your bits clean, replace them when they dull noticeably (not when they're completely shot), and store them properly. A dull bit creates heat, rough cuts, and unnecessary router strain. It's a false economy to keep using a worn bit to save money.