What makes CNC machines so accurate and versatile?
This question must have crossed your mind if you’re looking to fabricate your parts using CNC machines. Without a doubt, the computerized nature of computer numeric control (CNC) machining plays a significant role in the machine’s accuracy. But what really makes CNC machines so versatile is the near-endless options you’ve got with cutting tools.
This article presents nine different types of 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.
Some Materials Used in CNC Machines’ Cutting Tools
Carbon steel is a steel alloy containing up to 1% carbon and up to 1.6% manganese by weight. Cutting tools made of carbon steel are quite affordable and offer high machinability. They are ideal for low-speed CNC machining of soft metals like aluminum, brass, and magnesium (Related Post: CNC Machining Magnesium: What are the Safety Concerns?).
High-speed steel is just carbon steel alloyed with additional materials like molybdenum, tungsten, chromium, cobalt, and vanadium. These alloying elements give HSS its high temperature and abrasion resistance and durability.
Cutting tools made of high-speed steel are ideal for continuous high-speed cutting. You can use them to cut both ferrous and nonferrous metals.
Carbide is composed of a combination of carbon and tungsten. Cutting tools made of carbide are generally resistant to heat, rust, and scratches. In fact, they last much longer than steel cutting tools in extreme conditions.
Cutting tools made of ceramic offer heat and corrosion resistance. They are also chemically stable since ceramic doesn’t react with most metals that may be used as workpieces.
Ceramic cutting tools have high cutting efficiency and are ideal for high-speed semi- and final finishing of hard steels, cast iron, and superalloys.
Now let’s take a look at the different types of tools used in CNC machines.
Types of CNC Cutting Tools (With Illustrations)
#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.
CNC machining drill bits typically come in three varieties-center, twist, and ejector drills- with each type having different important functions.
You should use center drill bits to precisely create small spots on the workpiece, which can then be drilled properly using a twist drill. In contrast, ejector drills are better suited for deep hole drilling.
#2 End Mill
End mills are similar to drill bits but are much more versatile in the operations they perform. 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).
End mills come in many varieties, with the roughing end mill type being the most common. Roughing end mills have up to eight flutes, just like the regular end mills. However, the flutes in the roughing end mills are serrated, allowing you to remove larger amounts of materials compared to the regular end mills.
#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 are specialty cutting tools that allow you to make flat sections of the workpiece before detailed cutting operations are carried out. This tool features a solid body with multiple interchangeable cutter inserts that can be swapped as needed.
You might want to consider using a “side and face cutter” for more demanding complex operations. For instance, side and face cutters allow you to cut a groove or slot in a workpiece while also cutting the sidewalls of the workpiece.
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. They are similar to taps in the purpose they serve. But 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 that make broad or shallow cuts and produce a smooth surface finish. Compared to most face mills, fly cutters are inexpensive and offer a better surface finish. It should be your go-to tool for plane surfacing operations.