CNC Cutting Tools: 12 Types, Materials and Uses

CNC cutting tools are the rotating or stationary tools that remove material on a CNC machine: drills, end mills, face mills, reamers, taps, thread mills and special cutters. The tool type decides which feature you can make; the tool material, coating and holder decide how fast and how accurately you can make it.

At Davantech we do not sell cutting tools. We use them every day in our Dongguan factory to make accurate, repeatable CNC machined parts in aluminum, stainless steel, brass and engineering plastics. This guide shows the 12 tool types we use most, how to choose a tool and coating for each material, and how tool holders affect accuracy.

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Tool types

12 Types of CNC Cutting Tools

These are the cutting tools we use most to make metal and plastic parts. Knowing what each tool can do helps you design parts that are easy, and therefore cheaper, to machine.

1. Drill Bits

Drill bits have two helical flutes and a conical tip, usually with a 118° to 140° point angle; the flutes carry the chips out of the hole. Center drills spot the hole position, twist drills drill it, and ejector drills are used for deep holes.

2. End Mill

The basic milling tool: it cuts with its sides and its tip and removes large volumes of material. Roughing end mills have interrupted cutting edges to remove material fast; a finishing end mill then leaves a clean surface.

3. Ball End Mill

Has a rounded tip for spherical cavities and curved 3D surfaces. It makes many closely spaced passes to avoid small ridges, so it is slower than a standard end mill, but the result is a smooth contour.

4. Face Mill

Large-diameter mill with replaceable carbide inserts that cuts with its bottom face. Usually the first operation on raw stock: it makes surfaces flat and square at high speed.

reamers

5. Reamers

A drill cannot make a hole to a tight tolerance. A reamer finishes a slightly undersized drilled hole to an exact diameter, such as H7, for press fits, sliding fits and dowel pins. More in what is reaming.

6. External Round Mill

Also called a corner rounding mill. It forms a radius on an outside edge instead of a sharp corner, which looks better, is safer to handle and reduces stress concentrations.

7. Hollow Mill

Similar to an end mill, but with a hole in the center. By cutting straight down it leaves a round stud or pin of an exact diameter standing on the part.

8. Thread Tap

Cuts or forms internal threads in a drilled hole, metric or UNC/UNF, for the screws that mount electronics or join mechanical parts. Threaded holes are among the most common features in machined parts.

9. Thread Milling Cutter

Mills a thread by moving along a helical path. One thread mill can make internal and external threads in several diameters with the same pitch, and a broken thread mill rarely ruins the part.

10. Fly Cutter

A single cutting tip on a wide body. It makes large surfaces flat and smooth in a few passes and leaves a fine finish, at low tool cost.

11. T-Slot Mill / Slitting Saw

T-slot mills cut undercuts and grooves at right angles to the tool axis. Slitting saws make thin, deep cuts, for example to split a clamp or cut a narrow slot.

12. Countersink Mill

Machines chamfers on holes and edges, and countersinks for flat-head screws. A lower spindle speed prevents chatter and gives a clean, round countersink.

Quick reference

CNC Cutting Tools Compared: Operation, Result and Tool Material

Cutting tool	Operation	What it produces	Typical tool material
Drill bit	Drilling	Round holes. Center drills spot the hole, twist drills drill it, ejector drills handle deep holes.	HSS or solid carbide
End mill	Side and face milling	Pockets, slots, profiles and contours. Roughing end mills remove stock fast before finishing.	Solid carbide or HSS
Ball end mill	3D contour milling	Curved surfaces, spherical cavities and fillets, using many closely spaced passes	Solid carbide
Face mill	Face milling	Large flat, square surfaces. Usually the first operation on raw stock.	Steel body with indexable carbide inserts
Reamer	Reaming	A pre-drilled hole finished to a tight diameter tolerance and smooth bore	Solid carbide or HSS
External round mill	Corner rounding	A radius on external edges instead of a sharp corner	Solid carbide or HSS
Hollow mill	Hollow milling	A cylindrical stud or boss of set diameter, cut by plunging straight down	HSS or carbide
Thread tap	Tapping	Internal threads in drilled holes, for screws that mount electronics or mechanical parts	HSS or HSS-cobalt
Thread cutting mill	Thread milling	External threads such as those on bolts, cut by a circular toolpath	Solid carbide
Fly cutter	Facing	A smooth, flat surface on a rough face, cut quickly by a single tip on a long arm	Carbide or HSS cutting bit
T-shape mill / slitting saw	Slotting and slitting	Undercuts, T-slots and grooves at right angles to the tool axis. Slitting saws make thin, deep cuts.	HSS or carbide
Countersink mill	Countersinking	Conical recesses so flat-head screws sit flush, and chamfers on hole edges	HSS or carbide

Tool material depends on the workpiece. HSS suits aluminum and brass at moderate speeds; carbide holds its edge at higher speeds and on stainless steel.

How to choose

Which Cutting Tool for Which Job?

The operation decides the tool type; the workpiece material decides the flute count, the tool material and the coating. This is how we choose in practice.

Feature to make	Tool	Aluminum	Steel and stainless	Plastics (POM, PA66, PEEK)
Large flat faces	Face mill or fly cutter	Sharp polished inserts, high speed	Coated carbide inserts, lower speed	Fly cutter or sharp end mill for a clean surface
Pockets, slots, profiles	End mill	2 to 3 flutes, polished, uncoated or DLC	4 or more flutes, TiAlN coated	1 to 2 flutes, very sharp, polished
3D curved surfaces	Ball end mill	Solid carbide, small step-over	Coated solid carbide	Sharp solid carbide, light cuts
Holes	Center drill, then twist drill	Carbide or HSS with wide flutes for chips	Coated carbide, coolant through the tool for deep holes	Sharp drill, low feed so the plastic does not melt
Precise holes (H7)	Drill undersize, then reamer	Carbide reamer	Carbide reamer, coated	Sharp reamer; plastic holes shrink slightly after cutting
Threads	Tap or thread mill	Forming tap (no chips) or cutting tap	Thread mill for large or costly parts	Cutting tap, or threaded insert for repeated assembly
Chamfers and countersinks	Chamfer or countersink mill	Same tool on all materials; adjust speed to the material

Tool materials

What Cutting Tools Are Made Of

The tool material decides how hot a tool may get, and so how fast it can cut. Harder materials cut faster but are more brittle.

Carbon tool steel

The cheapest option. Loses its hardness above about 200 °C, so only for low speeds, hand tools and soft materials.

High-speed steel (HSS)

Tough and low cost, keeps its hardness up to about 600 °C. Used for drills, taps and reamers and for small batches. Cobalt grades (HSS-Co) last longer.

Solid carbide

Tungsten carbide in a cobalt binder. Much harder and more heat resistant than HSS and allows several times higher cutting speeds, but more brittle. Most CNC end mills and inserts are carbide.

Ceramic and CBN

Extremely hard and heat resistant. For high-speed finishing of hardened steel and cast iron; too brittle for interrupted cuts and not used on aluminum.

Coatings

Cutting Tool Coatings Compared

A coating is a thin hard layer on a carbide or HSS tool. It reduces friction and heat and makes the tool last longer, but the wrong coating does more harm than good: coatings that contain aluminum react with aluminum workpieces and cause material to stick to the cutting edge.

Coating	Color	Best for	Avoid on
Uncoated, polished carbide	Silver	Aluminum, copper, brass and plastics: the sharpest edge	Steel at high cutting speed
TiN (titanium nitride)	Gold	General purpose, HSS drills and taps	Hard steels at high temperature
TiCN (titanium carbonitride)	Blue-grey	Steel and cast iron, interrupted cuts	Aluminum
TiAlN / AlTiN	Violet to black	Steel, stainless steel and hardened steel, high speed or dry cutting	Aluminum
DLC (diamond-like carbon)	Black	Aluminum, copper, plastics and composites	Steel and stainless steel

CNC tooling

Tool Holders: the Part of CNC Tooling Nobody Sees

A cutting tool is only as accurate as the holder that clamps it in the spindle. If the tool runs off-center (runout), one flute does most of the cutting: the tool wears faster, the surface gets marks and holes come out oversize. Most vertical machining centers use a BT40 or SK40 taper; the holder sits between that taper and the tool.

Holder	How it clamps	Typical runout	Used for
ER collet chuck	Slotted collet squeezed by a nut	About 0.01 to 0.02 mm, less with precision collets	General milling, drilling and tapping
Shrink-fit holder	Holder is heated, tool inserted, grips on cooling	About 0.003 mm	High-speed finishing, long-reach tools
Hydraulic chuck	Oil pressure presses a sleeve onto the shank	About 0.003 mm	Reamers and finishing, good vibration damping
Side-lock (Weldon)	Set screw on a flat on the shank	Higher than the others	Heavy roughing where the tool must not pull out
Tapping chuck	Floating holder with axial compensation	Not critical	Tapping threads

Two habits matter as much as the holder: keep the tool stick-out as short as possible (vibration rises fast once the tool sticks out more than about 3 times its diameter), and measure every tool length before the first cut. See how we apply this in our CNC milling and CNC turning work, and how tolerances are specified in CNC machining tolerances explained.

FAQ

CNC Cutting Tools Questions

How many types of cutting tools are used in CNC machining?

There are dozens of special tools, but 12 types cover most work: drill bits, end mills, ball end mills, face mills, reamers, corner rounding mills, hollow mills, taps, thread mills, fly cutters, T-slot mills and slitting saws, and countersink mills.

What is the difference between an end mill and a drill bit?

A drill bit cuts only with its conical tip and makes round holes by plunging straight down. An end mill cuts with its sides and its end, so it can also move sideways to make pockets, slots and contours, and it removes far more material per pass.

When do you use a ball end mill instead of a standard end mill?

For curved 3D surfaces and spherical cavities. A ball end mill makes many closely spaced passes to avoid small ridges, so it is slower than a flat end mill, but it gives a smooth contour.

Why is a reamer needed if a hole is already drilled?

A drill cannot hold a tight diameter tolerance or leave a smooth bore. A reamer removes 0.1 to 0.3 mm from a slightly undersized drilled hole and brings it to an exact size, typically H7, for press fits, sliding fits and dowel pins.

How are internal and external threads machined?

Internal threads are cut or formed with a tap, or milled with a thread mill. External threads are turned on a lathe or milled with a thread mill. Thread mills are preferred on large or expensive parts, because a broken thread mill rarely ruins the part.

Which tool coating is best for machining aluminum?

Uncoated, polished carbide or a DLC coating. Coatings that contain aluminum, such as TiAlN, react with aluminum and make chips stick to the cutting edge; those coatings are made for steel and stainless steel.

What materials are CNC cutting tools made from?

Mainly high-speed steel (HSS) and solid carbide, with ceramic and CBN for hardened steel. Carbide is used for most CNC milling because it allows much higher cutting speeds; HSS is still common for drills, taps and reamers.

Does Davantech sell CNC cutting tools?

No. We use cutting tools to make CNC machined parts for our customers. If you need parts machined, send a STEP file and drawing for a quote.

Need parts machined?

We use these tools every day to make CNC parts in aluminum, stainless steel, brass and plastics. Upload your STEP file for an instant price, or send drawings for a quote with DFM comments within 24 to 48 hours.

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