A guide to cutters for the milling machine

Milling machines are versatile tools in manufacturing and metalworking, capable of removing material with precision to create intricate shapes and surfaces. The effectiveness of a milling operation relies heavily on the type of cutting tool used. Different milling cutters are designed for specific tasks, materials, and geometries. Understanding these variations is crucial for selecting the right tool for a given application, ensuring efficiency, accuracy, and desired surface finish.

Here's a guide to some of the most common milling cutters used on milling machines:

End Mill

One of the most fundamental and widely used milling cutters is the end mill. It has cutting teeth on both its end face and its periphery, allowing it to cut axially (plunge), radially, or both simultaneously. End mills are incredibly versatile and are used for a wide range of operations including:

• Slotting: Creating channels or slots in a workpiece.
• Profiling: Cutting along an external or internal boundary to create a specific shape.
• Contouring: Machining curved surfaces.
• Plunging: Moving directly into the material like a drill bit (only with centre-cutting end mills).
• Face Milling: Machining a flat surface (though face mills are typically more efficient for larger areas).

Variations of End Mills:

• Square End Mill: Has sharp, 90-degree corners, ideal for cutting square slots, pockets, and edges.
• Ball Nose End Mill (Ball Mill): Features a hemispherical cutting end, perfect for machining 3D contoured surfaces, mold cavities, and fillets where a rounded transition is required.
• Radius End Mill (Corner Radius Mill): Has a rounded corner with a specific radius, offering a compromise between a square end mill and a ball nose end mill. It's used to create a rounded edge or reduce stress concentrations in corners.
• Roughing End Mill (Hog Mill): Designed for high material removal rates. It has a serrated tooth profile that breaks chips into smaller pieces, reducing cutting forces and improving chip evacuation. This allows for deeper cuts and higher feed rates during the initial roughing stages.
• Finishing End Mill: Designed to produce a smooth surface finish and accurate dimensions after roughing operations. They typically have more flutes and a refined cutting edge geometry.

End mills come in various numbers of flutes (the helical grooves that remove chips), typically ranging from two to multiple flutes. The number of flutes affects chip evacuation, tool strength, and the achievable surface finish. They are available in materials like High-Speed Steel (HSS), Cobalt HSS (HSCO), and Solid Carbide, with various coatings to enhance hardness, wear resistance, and lubricity for different workpiece materials.

Face Mill

Face mills are designed specifically for face milling operations, which involve machining a flat surface perpendicular to the cutter's axis of rotation. They are highly efficient for removing large amounts of material over a wide area, producing a flat and often smooth surface finish.

• Key Characteristics: Face mills are typically larger in diameter than end mills and have multiple indexable inserts positioned around the periphery of the cutter body. These inserts are the cutting edges and can be replaced when worn, making face mills cost-effective for heavy-duty milling.
• Applications: Primarily used for facing large surfaces on workpieces, preparing surfaces for subsequent machining operations, and ensuring flatness and squareness.

Slot Drill

Similar in appearance to a square end mill, a slot drill is specifically designed for cutting slots and keyways from solid material. A key distinction is that slot drills are typically centre-cutting, meaning the cutting edges extend to the very centre of the tool, allowing them to plunge into the material.

• Applications: Creating precise slots, keyways for shafts and pulleys, and can also be used for pocketing and some limited profiling.

Shell Mill

Shell mills are similar to face mills in that they are used for face milling and have indexable inserts. However, they are typically mounted on an arbor rather than having an integrated shank.

• Applications: Used for face milling large surfaces and also for shoulder milling and some contouring applications, offering high material removal rates.

Side and Face Cutter

A side and face cutter has cutting teeth on its periphery and on both sides. This design allows it to cut on its sides as well as its diameter simultaneously.

• Applications: Ideal for milling slots, grooves, and keyways where the width and depth of the cut are important. They are also used for straddle milling (cutting two parallel vertical surfaces simultaneously) and for cutting shoulders.

Angle Cutter

Angle cutters are designed to mill angular surfaces. They have cutting edges machined to a specific angle relative to the cutter's axis.

• Types:
  • Single-Angle Cutter: Has cutting teeth on a conical surface at a single angle. Used for chamfering, bevelling, and cutting dovetails.
  • Double-Angle Cutter: Features V-shaped teeth with two conical faces at an angle. Used for cutting V-grooves, serrations, and sometimes for milling gear teeth.

T-Slot Cutter

T-slot cutters are specialized cutters used to mill T-shaped slots, commonly found on machine tables and fixtures for clamping purposes. They have a narrow shank and a wider cutter at the end.

• Process: A vertical slot is typically milled first with an end mill, and then the T-slot cutter is used to mill the wider, horizontal part of the "T".

Dovetail Cutter

Dovetail cutters are specifically designed to cut dovetail-shaped slots or grooves, which are often used for machine slides, jigs, fixtures, and woodworking joints due to their interlocking nature. They have a flared cutting profile that matches the desired dovetail angle.

• Applications: Creating male and female dovetail profiles for various mechanical and structural applications.

Fly Cutter

A fly cutter is a simple and economical milling cutter that uses a single-point cutting tool (often a modified lathe tool bit) mounted in a body that rotates. The cutting tool is set at a distance from the center of rotation, and as it spins, it sweeps across the workpiece, removing material.

• Applications: Primarily used for face milling large, flat surfaces and achieving a very smooth surface finish, especially on smaller milling machines. They are often used for finishing passes rather than heavy material removal.

Choosing the appropriate milling cutter is a critical step in any milling operation. Factors such as the material to be machined, the desired geometry, the required surface finish, the available machine rigidity, and the production volume all influence the selection of the optimal cutter type, material, coating, and geometry. A thorough understanding of these different cutters and their applications is essential for achieving efficient and accurate machining results