9 popular CNC cutting tool types

Selection of proper CNC cutting tool types

There are so many CNC cutting tool types out there, they should definitely have the right one for the job. This article presents nine different types of cutting tools used in CNC machines and their functions.

Understanding these tools’ functions is an important step you need to take before doing business with any CNC machine shop. If your design requires a different tool, the machine shop may need to spend extra time or money sourcing a custom tool.

#1 Drill Bits

Drill bits have a conical cutting point and a shaft with one or more flutes-the helical grooves that run down the exterior of the tool.

Drills are your standard tool for making holes in a material. Holes can be used for many things: clearance holes, threaded holes, press fits, or locating. Drills work for all of these.

As with other tools, there are standard sizes of drill bits. When you design a hole for your part, look up standard drill sizes so that you are making the machining process as easy as possible. Additionally, design all holes in your part to be the same size where possible to avoid unnecessary tool changes.

Drill bits used in CNC machining include:

• Twist drill: Used to make holes in the workpiece
• Center drill: Used to precisely locate a hole before drilling
• Ejector drill: Used for deep hole drilling

#2 End Mill

The square end mill is the most standard tool that every machine shop will have in multiple sizes. End mills are similar to drill bits but are much more versatile in the operations they perform. With cutting teeth at one end and on the sides, these tools can be used for facing the top and sides of a part. They typically have up to eight sharp flutes on their ends and sides, allowing them to remove large amounts of materials within a short period.

An end mill should be your go-to tool if you want to cut straight down into a material without requiring a pre-drilled hole (or spot).

Types of end mill include:

• Flat: General purpose flat-faced tool suitable for 2D features
• Ball nose: Tool with ball-shaped end that is suitable for 3D contours and curves
• Bull nose: Tool with flat bottom and rounded corner suitable for fillets and roughing

#3 Face Mill

More often than not, the starting material (or workpiece) used in CNC milling machines requires some sort of preparation before you can perform major milling operations.

Face mills consist of a solid body with interchangeable cutter inserts, usually made from carbide, that can be swapped as needed. They are used to make flat sections on the workpiece before detailed cutting operations are carried out. These tools are good for removing material from a wide area, making them great for an initial roughing pass to level off the face of your stock material, then you have a nice even surface to begin machining.

#4 Reamers

Reamers cannot be used to create a hole, but are very useful for widening an existing hole to the exact diameter needed, providing an exact hole diameter and an excellent surface finish.

Let’s say you need to create a 1/2” hole in a workpiece. You can proceed to use a 1/2” drill bit, right? Wrong! Do this, and you can expect to have an oversized hole when you’re done drilling your workpiece.

An ideal way to create this hole is to start with a smaller drill bit, say 31/64”, before widening the hole to 1/2” using a reamer. Reamers allow you to expand the size of existing holes while achieving dimensional accuracy and tight tolerances.

#5 Gear Cutters

As the name suggests, gear cutters are used to make gears for manufacturing industries. You can use it to fabricate a wide variety of gears, including spur, bevel, worm, screw, and helical gears.

#6 Hollow Mill

Hollow mills are pipe-shaped cutting tools with three or more cutting edges that enclose and revolve around a cylindrical workpiece. This cutting tool allows you to create a consistent pre-thread diameter quickly and efficiently. You can also use them in drill press work for finishing projections that must be in a given position.

#7 Thread Mill

As the name suggests, thread mills are CNC cutting tools used for cutting threads.

Many engineers prefer to make threads using taps, but threads can also be made with a CNC machine fitted with a thread mill. Unlike taps that cut only internal threads, CNC machines fitted with thread mills can cut both internal and external threads.

You should opt for thread mills if you’re looking to penetrate hard metals or asymmetrical parts.

#8 Slab Mill

Slab mills, also known as slab cutters or plain mills, are used to cut flat surfaces. These cutters typically only have teeth on their periphery and are ideal for creating wide and narrow cuts quickly.

#9 Fly Cutter

Fly cutters are single-point rotary tools, comprising one or two tool bits contained within a solid body that make broad or shallow cuts, producing a smooth surface finish. Less expensive than face mills while offering a better surface finish, fly cutters can nonetheless be used for similar purposes. It should be your go-to tool in your list of CNC cutting types for plane surfacing operations.

As an engineer, you may not be the one choosing the tools for your CNC machining operation. However, you can think critically about the design of your part to reduce the number of different tools used and ensure that the tools that are needed are standard and available at most machine shops.

Considering your tool selection is just one part of Design for Manufacturability. At TDB, we will optimize costs for your production demands. Leave us an RFQ to have a competitive quotation.