CNC (Computer Numerical Control) machining is an automated manufacturing process widely used in modern industry to produce components with high precision. From aerospace parts to automotive molds, CNC machines can consistently fabricate complex shapes to tight tolerances. However, the magic truly lies in the tools they employ – the cutting implements that actually shape the material.
Choosing the right CNC cutting tools is critically important for achieving precision, efficiency, and scalability in production. The correct tool can improve surface finish, reduce machining time, and extend tool life, whereas a poor choice might result in excessive wear, inaccurate parts, or machine downtime. This comprehensive guide is written for industrial users, manufacturers, engineers, and fabricators (particularly in the UK context) looking to optimise their use of CNC machining tools.
This article includes:
- What are CNC machining tools?
- 1. Routing tools (for CNC routers: wood, plastic, composites)
- 2. Cutting tools (e.g. end mills, face mills, slab mills)
- 3. Drilling tools (e.g. twist drills, centre drills)
- 4. Turning tools (e.g. carbide inserts, boring bars)
- 5. Milling tools (e.g. ball nose, flat end, chamfer mills)
- 6. Grinding and finishing tools (for post-processing and surface preparation).
This is a big guide, but scan through and you’ll find what you need!
What are CNC machining tools?
Definition and function
CNC machining tools are the cutting attachments used by CNC machines to remove material from a workpiece under programmatic control. In other words, if a CNC machine is the programmable device (e.g. a milling machine or lathe), the CNC tool is the actual cutter, drill, or bit mounted in the machine’s spindle or turret that does the cutting. A cutting tool is typically a hardened metal implement with sharp edges that shear away chips of material from the workpiece.
The CNC machine positions and moves the tool with computer precision, while the tool’s geometry (shape, sharpness, flutes, etc.) performs the material removal. It’s important to distinguish the machine from the tool: the CNC machine is the entire system (with motors, control, etc.), whereas CNC tools (often called cutting tools) are the interchangeable bits that actually contact the material. The machine provides motion and control, but the magic truly lies in the tools that achieve the desired shapes and finishes.
Tool operations
CNC tools enable a wide range of automated machining operations. Different tool types are designed for specific tasks such as cutting/milling, drilling, turning, routing, and engraving.
For example: a CNC milling cutter can profile or carve out pockets in metal; a drill bit bores precise holes; a turning tool on a CNC lathe cuts the outside or inside diameter of a rotating part; a router bit carves wood or plastic in a CNC routing machine; and special engraving bits can etch text or patterns.
In industrial CNC machining, these tools allow complex operations like contouring, slotting, boring, tapping, threading, and more – all with high repeatability.
The proper selection of tool type and parameters for a given operation is crucial. A sturdy twist drill will efficiently make a hole, but for cutting a complex 3D surface you’d use a ball-nose end mill instead.
Why tool choice matters
Using the right tool for the job underpins the quality and economics of CNC machining. Each CNC tool has its unique application and optimal operating range, and understanding these can “save both time and costs in the long run.
For instance, trying to machine hardened steel with an uncoated high-speed steel tool would result in very short tool life and poor results – a carbide or ceramic tool is needed for that task. Likewise, using an oversized cutter for a delicate feature could ruin a part’s accuracy.
The correct tool choice ensures precision (achieving tight tolerances and fine surface finishes), efficiency (removing material in the least time), and scalability (tools that hold up under production volumes). Industrial users therefore carefully select tooling for each job, often referencing tooling catalogs or suppliers.
Types of CNC machining tools
CNC machining tools can be classified into several major categories, each suited to different kinds of machining operations. Below we break down the main categories – cutting tools, drilling tools, turning tools, milling tools, routing tools, and grinding/finishing tools – with examples and their typical uses. A face milling cutter in action on a CNC milling machine, removing material from a metal workpiece. The spinning multi-point cutter (with yellow carbide inserts) is surfacing the top of the steel piece, producing blue metallic chips.
1. Routing tools (for CNC routers: wood, plastic, composites)
Routing tools refer to the cutters used in CNC routers, which are a type of CNC machine typically designed for softer materials like wood, plastics, MDF, composites, and sometimes aluminium. CNC routers often resemble large gantry mills but are optimised for sheet materials and high spindle speeds.
Routing tools are specialised cutters for CNC router machines. They enable high-speed cutting of sheet materials and wood without tearing the material. Many UK woodworking and sign-making businesses use CNC routers with such tools – e.g. sign makers might use V-bits to carve letters in acrylic sheets, while a furniture workshop uses end mills and ball nose bits to carve intricate designs in wood.
Browse our 3-axis CNC routers here and our 5-axis CNC routers here.
The tools for routers are similar in concept to end mills but have some differences in geometry to suit woodworking and plastics machining:
Spiral router bits (upcut/downcut)
These look like spiral end mills and often are made of solid carbide. An upcut bit has flutes that pull chips up and out of the cut (like a conventional end mill) – these are good for clearing chips in materials like plastic or when cutting wood all the way through (the downside is they can cause tear-out on the top surface of wood because they pull the fibers up).
A downcut bit pushes chips downward – this keeps the top surface of the wood clean (no splintering) but tends to push the chips into the cut, so it’s used for shallower cuts or with good vacuum extraction.
There are also compression bits which have an upcut geometry on the lower part and downcut on the upper part – these are used to cut clear through wood sheets without tear-out on either face (the downcut portion protects the top surface, the upcut portion protects the bottom surface, meeting in the middle).
Spiral bits are generally 2-flute or 3-flute and very sharp.
Straight router bits
These have cutting edges with no helix (straight flute). Often used on wood, especially in handheld routers, for simple grooving, etc. In CNC use, straight bits can be used for certain plastics or where you want to minimise lifting of material. However, they tend to heat up if chip evacuation is poor. They are best for shallow cuts in wood or laminate.
Specialty profile bits
In woodworking CNC, you might use v-groove bits (for engraving lines or lettering with a V profile), round-over bits (to round edges, similar to a corner rounder but often with a bearing in manual use – on CNC the bearing isn’t needed), ogee bits (for decorative edges), and so on. CNC routers often create signs, cabinets, and furniture components, so these bits allow decorative edges and engravings. For instance, a V-bit with 90° angle is commonly used to carve letters in a sign (V-carving) by varying depth.
Browse our CNC engraving machines.
Surfacing bits
Large flat router bits (with maybe 1″ diameter or more) are used to plane the surface of a wood slab or spoilboard. They act like a face mill but for wood/plastic, ensuring a flat reference surface.
Routing tools need to be run at high RPM (often 15,000–20,000 RPM or more) since they are usually smaller diameter and cutting softer material. They are often made from tungsten carbide or carbide-tipped steel, because wood and especially composites can be quite abrasive (some fiberglass or carbon fiber composites will even use PCD-tipped router bits for longevity). According to a guide, router bit materials mirror those of metal-cutting tools: HSS (for softer wood, but wears quickly), carbide-tipped (for longer life in wood), solid carbide (for the hardest woods, plastics, and nonferrous metals), and even PCD for extremely abrasive materials.
For example, a cabinet manufacturer in the UK cutting MDF panels on a CNC router might use 1/4″ carbide compression bits to get clean cuts through laminated boards. They’ll replace or sharpen these bits once the edges lose sharpness (dull tools in a router can burn the wood).
Check out the following CNC router brands:
2. Cutting tools (e.g. end mills, face mills, slab mills)
“Cutting tools” generally refers to the multi-point milling cutters used to remove material in CNC milling machines and machining centres. These tools have multiple cutting edges and are usually made of solid carbide or steel with carbide inserts.
In essence, cutting tools in the milling category are characterised by rotating multi-point cutters. They remove material by shearing off chips with each pass of a tooth. These tools can be oriented horizontally or vertically in the machine and come in various geometries for different tasks.
Milling cutters (end mills, face mills, etc.) are typically made from carbide or high-speed steel and may have 2 to 8 or more flutes (helical grooves). The flute count and geometry affect performance: e.g. a tool with fewer flutes has more space for chip evacuation and is often used in softer materials or aggressive cuts, whereas tools with more flutes can achieve finer finishes on harder materials but risk chip congestion.
Cutting tools in a CNC mill are usually held in tool holders or collets attached to the spindle, allowing quick changes. Overall, cutting tools (milling cutters) form the backbone of CNC machining, handling everything from rough material removal to fine finishing on a variety of materials.
Browse our CNC cutting machines.
Common examples include end mills, face mills, and slab mills:
End mills
The most ubiquitous milling cutter, an end mill is a cylindrical tool with cutting teeth at the end and often on the sides as well. End mills come in various diameters and shapes (flat end, ball-nose, corner radius, etc.) and are used for profile milling, slotting, pocketing, and contouring. They can cut in the lateral direction and (if the end has teeth) plunge vertically into material. End mills are truly the workhorses of CNC milling – the standard, and most commonly used, form of milling cutter.
Face mills
Face mills are large-diameter cutters, typically with replaceable carbide insert teeth, used to machine flat surfaces very efficiently. They mount to the spindle (often via a shell mill arbor or similar) and have multiple cutting inserts around the periphery. As the name implies, face mills are used mainly for “facing” operations – surfacing the face of a workpiece to make it flat.
For example, after a steel block is rough-cut, a face mill might be passed over it to create a smooth, uniform face. Face mills cut away material from the workpiece surface, creating flat surfaces and curved edges on parts like dies, molds, and machined components.
Slab mills
Also known as plain milling cutters, slab mills are an older style of large rotary cutter used on horizontal mills. They have a broad cylindrical shape with cutting teeth on the periphery only (no teeth on the face of the cutter). Slab mills are used for heavy-duty material removal on wide, flat surfaces – similar to face mills, but typically in horizontal milling setups.
In modern CNC shops, face mills with indexable inserts have largely taken over the role of slab mills, but the term may still be used for any large rotary cutter that planes a surface.
3. Drilling tools (e.g. twist drills, centre drills)
Drilling tools are cutters designed to create holes in the workpiece. The most common drilling tool is the twist drill bit, recognisable by its spiral flutes. In CNC machining (using either a drill press, mill, or even a lathe’s drilling function), twist drills are used to drill holes of various diameters and depths. These tools typically have two cutting edges at the tip (formed by a point angle) that bore into the material while the flutes carry chips out of the hole.
Twist drills are commonly made from high-speed steel or carbide and come in standard sizes (e.g. metric or imperial) for clearance holes, tapped holes (to be threaded later), etc.
In an industrial CNC program, drilling might be a preliminary operation: for example, drilling bolt holes into a steel plate. CNC control allows for techniques like peck drilling (periodically retracting to clear chips) to drill deep holes. In addition to standard drill bits, there are specialised drilling tools used in CNC machining:
Centre drills / Spot drills
These are short, rigid drills with a thick body and a very pointy tip, used to start holes accurately. A centre drill creates a small conical hole that “centres” a subsequent twist drill, preventing it from wandering off position. In lathe work, a centre drill is used to create a conical seat (centre hole) at the end of a workpiece to accept a live centre.
In CNC milling, a spotting drill (a similar tool) is often used to mark the location of a hole before the full-size drill goes in. This ensures high positional accuracy for the hole. Centre/spot drills have a short length, so they are very stiff.
Typically, one would spot drill a hole location, then switch to a longer twist drill to drill the full depth – the pre-made spot helps guide it. (Note: sometimes “centre drill” refers to a combined drill and countersink tool used specifically for lathe centres, whereas “spot drill” is purely for starting holes; but the function is similar.)
Other drill types
Depending on the application, CNC machining might use step drills (which drill holes with two or more diameters in one go), reamers (to finish holes to a very precise size and smoothness), counterbores (tools to create a flat-bottom enlarged recess for screw heads), and countersinks (conical tools to make a tapered seat for flat-head screws).
There are also gun drills for very deep holes (common in specialised CNC machines) and indexable insert drills for large diameter holes in production (these look like a cross between a drill and a milling cutter, with carbide inserts on a drill body). For thread-making, taps (for internal threads) or thread mills may be used, but those are considered a separate category from basic drilling.
CNC drilling operations typically involve high spindle speeds and careful feed control to produce clean, straight holes. Spotting drills, peck drills, screw-machine length drills, and reamers each serve specific purposes in hole-making.
For example, spotting drills (for producing shallow or pilot holes), peck drills (for chip breaking in deep holes), screw machine drills (short rigid drills for holes without a pilot), and chucking reamers (for enlarging and finishing existing holes) are all part of a machinist’s toolkit.
In practice, a CNC program might use a spot drill to start, then a twist drill to get close to final size, and finally a reamer to achieve a precise diameter and smooth finish (common for dowel pin holes). Drilling tools are often made from HSS with cobalt or solid carbide for tougher jobs; coatings like TiN are frequently used to extend their life. UK suppliers such as Cutter Shop provide a huge array of drilling tools for industry. Selecting the right drill bit (correct tip angle, length, material, and coating) for the material can greatly improve hole quality and tool longevity.
4. Turning tools (e.g. carbide inserts, boring bars)
Turning tools are used in CNC lathes (turning centres) for machining parts that are rotated (typically cylindrical parts like shafts, bushings, etc.). Unlike milling and drilling tools which rotate themselves, turning tools usually remain stationary in a turret or tool post while the workpiece spins.
These tools typically have a single cutting point that is pressed against the rotating workpiece to remove material. Common turning operations include facing (cutting the flat face of a part), turning (cutting along the diameter to reduce it, creating a cylindrical surface), grooving, parting (cut-off), boring (internal turning to enlarge a hole), and threading on a lathe.
In modern CNC lathes, turning tools most often use carbide inserts. These are small interchangeable cutting tips (usually triangular, square, diamond-shaped, etc.), often with multiple cutting edges, that screw or clamp into a tool holder. The insert provides a precision cutting geometry (sharp point with specific rake angles, nose radius, etc.) and can be easily replaced when worn, rather than replacing the whole tool. Carbide inserts are extremely common in industry for turning steel, stainless, cast iron, etc., because they can withstand high cutting speeds and offer long life. Different insert shapes and grades are available for roughing versus finishing, for different materials, and for various operations (e.g. a specific insert for threading will have a thread profile form).
Some examples of turning tools and uses:
General turning/facing tool
A rhombic (diamond-shaped) insert in a holder at a certain lead angle can be used to turn down a shaft’s diameter or face the end of a bar. There are roughing inserts (stronger cutting edge for heavy cuts) and finishing inserts (sharp with a small nose radius for fine finishing cuts).
Boring bar
This is essentially an internal turning tool. A boring bar is a long tool that can reach inside holes to enlarge and finish them. It holds a tiny insert or cutting tip at its end. CNC lathes (or milling machines) use boring bars to machine precise internal diameters that can’t be made by drilling alone (for example, a bearing housing bore). Boring bars must be stiff to avoid chatter. Carbide shank boring bars or anti-vibration (damped) boring bars are often used for deep internal cuts.
Parting (cut-off) tool
A blade-like tool (often with insert) used to cut off (sever) the finished part from the stock material. It plunges radially into the rotating work to cut all the way to the centre. Parting tools must be very rigid and sharp to cut without causing excessive deflection or a poor finish. Modern indexable parting tools have carbide inserts designed for this task.
Grooving and threading tools
These are similar to parting tools in that they cut a specific profile into the work. A grooving tool cuts a channel (either external or internal groove), and a threading tool cuts helical threads (with the insert shaped to form the thread profile, e.g. 60° for metric/UN threads). Threading inserts are precisely formed to create the correct thread geometry when fed along the part at a synchronised speed.
Turning tools are characterised by their single-point cutting action. Turning employs single-point cutting tools to remove material from the rotating workpiece, with different tool shapes for roughing, finishing, facing, threading, undercutting, parting, and grooving.
This means each distinct operation on a lathe might require a different shaped tool or insert. In an industrial CNC lathe turret, you might find a turning tool for general cuts, a facing tool, a boring bar, a threading tool, and a part-off tool all mounted and ready to be indexed into position. Because lathe tools are critical for maintaining part geometry (diameters, roundness, etc.), they must be kept sharp and rigid.
Carbide inserts often have a coating (TiN, TiCN, etc.) to improve wear life. Some lower-cost or older applications still use HSS tool bits ground to shape, especially for softer materials or for custom profiles. But in professional manufacturing, insert tooling dominates for efficiency.
5. Milling tools (e.g. ball nose, flat end, chamfer mills)
This category overlaps somewhat with the earlier “cutting tools,” since end mills are a type of milling tool. However, here we highlight specific milling cutter geometries and specialty tools that are notable in CNC machining:
Flat end mill
A flat end mill (also called square end mill) has a flat cutting face at the tip. It is used for machining flat-bottomed pockets, slots, and shoulders. When it cuts, it leaves a 90° step at the wall of the cut. Flat end mills are extremely common – for example, if you need to mill a flat pocket or face off the top of a part, a flat end mill is ideal. They come in various sizes and flute counts. They cannot drill straight down effectively unless centre-cutting (able to cut at the centre), so often one uses a helix or ramping motion to enter the material. Flat end mills produce sharp edges at the intersection of the floor and wall of a pocket.
Ball nose end mill
A ball nose mill has a hemispherical (rounded) end, which forms a rounded contour in the workpiece. These are crucial for 3D contour milling – for example, in mold making or complex aerospace parts, where you have curved surfaces. A ball nose tool can be swept along a surface to carve a smooth 3D shape. Because the tip is rounded, the cutter leaves a very smooth finish with no sharp steps.
Ball nose mills are used extensively in 5-axis CNC machining for creating organic shapes, turbine blades, impellers, etc. They also work well for gentle engraving on curved surfaces. The trade-off is that at the very tip (the centre of the ball) the surface speed is zero during cutting, so a ball nose can sometimes rub instead of cut if not properly angled or if the material is not soft.
Typically, one uses small step-overs when finishing with a ball nose to ensure a good surface.
Chamfer mill (angled end mill)
Chamfer mills are cutters with an angled cutting edge, used to create chamfers (beveled edges) on a workpiece or to deburr sharp edges. A common chamfer tool might be a 90° included angle (45° per side) cone-shaped tool. By running it along an edge, it cuts a consistent bevel, which is important for part safety (removing sharp edges) and for assembly (e.g. a chamfer to help a bolt head seat or to lead into a hole).
In CNC operations, chamfer mills are often called countersink tools if used for making a conical seat in a hole. They can be used to chamfer edges of pockets, holes, and the outer profile of parts.
Many CAM software will have a chamfering operation where you select edges to chamfer and the machine will use a chamfer mill to lightly cut those edges. Chamfer mills come in various angles (60°, 90°, etc.) depending on the needed bevel. They are typically solid carbide or HSS. A small example: after milling a sharp-edged aluminium bracket, a machinist might use a chamfer mill to put a 0.5 mm x 45° bevel on all edges, preventing cuts and cracks. Chamfering is a quick finishing step.
Corner rounding end mill
This is a specialised tool used to put a radius on an edge (the opposite of a chamfer). It has a quarter-circular profile. For instance, if you want to round off (fillet) the edges of a part, a corner-rounding end mill can do that in one pass, leaving a nicely radiused edge.
T-slot cutters, dovetail cutters, woodruff key cutters
These are form tools (often resembling a disc or an L-shape) used to cut special features like T-slots (for table fixtures) or dovetail slides. They are essentially end mills with a specific profile. You first mill a straight slot with a normal end mill, then use a T-slot cutter with a larger cutting head that undercuts the sides of the slot to form a T-shaped channel (common on machine tool tables for clamping). Dovetail cutters similarly cut angled slides (common in tooling and slides for machine parts).
Fly cutters
A fly cutter is a single-point tool (often just a piece of HSS or carbide) mounted in a rotating body, used on mills to create very fine finishes on large flat areas. They are more often seen in manual machining, but a CNC can use a fly cutter at slow feed to achieve a near-ground surface finish on something like an aluminium instrument panel. They are simple but effective for certain surface finish needs.
Many of these milling tools (ball nose, chamfer, etc.) are technically varieties of end mills or face mills, but are worth separate mention because they fulfill specific tasks. To illustrate, there are multiple different types of end mills for milling different shaped slots, such as square, ball-nose, and radius end mills… others are designed with specific function in mind, like roughing and finishing end mills. This means a CNC machinist will choose a particular end mill geometry depending on the feature of the part.
In UK manufacturing, where high mix low volume production is common, having the right assortment of milling tools on hand (from roughers to ball noses to chamfer tools) is important for quick turnaround.
6. Grinding and finishing tools (for post-processing and surface preparation)
Not all CNC “machining” involves cutting with fluted tools or inserts – there are also abrasive tools and attachments that handle grinding and finishing operations. CNC grinding machines exist as a class of their own (CNC cylindrical grinders, surface grinders, etc.), which use a grinding wheel as the cutting tool. Additionally, CNC machining centres can be equipped with abrasive finishing tools (like grinding bits or abrasive brushes) to perform in-situ finishing after milling.
In CNC grinding machines, the tool is typically a rotating abrasive wheel made of bonded abrasives (aluminum oxide, silicon carbide, diamond, etc.). Grinding is a subtractive process but differs from milling in that it uses countless hard abrasive grains on the wheel’s surface to wear away material at a very fine scale. Grinding is a finishing process that uses an abrasive wheel to achieve extremely smooth surfaces or precise geometrical shapes on the workpiece.
For example, after a CNC lathe turns a hardened shaft, a CNC cylindrical grinder might grind it to achieve an even tighter tolerance or smoother surface (grinding can reach surface finishes in the single-digit microinch Ra, and very precise diameters). In tool and die making, CNC surface grinders grind flat surfaces to high precision, using grinding wheels as the tool. The grinding wheel itself needs periodic dressing (sharpening) to maintain its cutting ability.
Common abrasive tool materials include alumina (Al₂O₃) wheels for steels, carbide grinding with silicon carbide or diamond wheels, and CBN wheels for hardened steels. UK manufacturing uses CNC grinding heavily in aerospace, automotive, and tooling industries for polishing components or achieving tolerances that milling alone can’t.
Some examples:
- Abrasive stones or sticks
- Small grinding stones or mounted points can be held in a tool holder to grind or polish specific features. For instance, a tiny mounted stone might be used to polish a fillet or remove burrs in a metal part.
- Sanding and polishing attachments
- There are tools like flap wheels, sanding discs, or even belt attachments that can mount on CNC equipment. They can sand wood surfaces or polish metal. A CNC router, for instance, might swap to a sanding head to finish sand a carved wood panel.
- Abrasive brushes and honing tools
- These are “brush-like” tools with abrasive bristles or pads (such as nylon brushes impregnated with abrasive grit, or flexible honing tools like the “Flex-Hone”). They can deburr edges and polish surface profiles. Such tools can be integrated into CNC machines to automate deburring which would otherwise be manual. These tools remove minimal material – just enough to smooth surfaces or take off sharp burrs – and are designed not to shed excessive grit (to avoid contaminating the machine).
Using grinding or abrasive tools in CNC is often about improving surface quality or preparing a part for its end use. For example, after CNC milling a medical implant, a shop might use a series of abrasives to polish it to mirror finish. Or an engine part might be finish-ground at critical surfaces for accuracy. In the UK, where high-value manufacturing is common (like aerospace engine components), CNC grinding is a key process – companies like Rolls-Royce use CNC grinding to finish turbine blade profiles to tight aerodynamic specs.
Another aspect of finishing is tool sharpening – CNC tool and cutter grinders (a type of CNC machine) use grinding wheels to sharpen end mills, drills, and other cutters to like-new condition. Solid tools like HSS end mills and drills can be reground several times. Carbide tools can also be resharpened, although it’s more common for inserts to be indexed or replaced
