Guide to 15 Essential Milling Types and Their Industrial Uses

Milling is a subtractive manufacturing process that employs rotary cutters to remove material from workpieces. Unlike turning which primarily creates rotational symmetry, milling can produce complex geometries including planes, curves, grooves, and holes. Its versatility and precision make it indispensable across aerospace, automotive, mold-making, medical device manufacturing, and numerous other industries.

The milling process involves four critical elements:

• Workpiece: The raw material being machined, typically metal but also plastics or composites.
• Milling cutter: Rotary tools with single or multiple cutting edges that remove material. Selection depends on specific machining requirements.
• Milling machine: Equipment that provides power and control, securing workpieces while driving cutter movement. Modern CNC systems enable high-precision automated operations.
• Cutting parameters: Variables including speed, feed rate, and depth of cut that directly affect quality and efficiency.

Milling techniques can be categorized by cutter motion (face milling, peripheral milling) or workpiece geometry (surface milling, contour milling). Below we examine fifteen essential milling variants in detail.

This surface-finishing method employs face mills with cutting edges on the tool's end surface. The rotating cutter progressively removes material to create flat, smooth surfaces, particularly effective for large workpieces like mold bases or machine beds.

Tool: Large-diameter face mills with end-mounted cutting edges.

Applications: Surface finishing of large components, creating precise flat surfaces, machining recesses and steps by flattening and smoothing material.

Using slot mills or end mills resembling circular saw blades, this process cuts channels of specific width and depth into workpieces, commonly applied for keyways and T-slots.

Tool: Slot mills (peripheral cutting edges) or end mills (side cutting edges).

Applications: Machining various groove types including keyways, T-slots, and guide rails.

Highly versatile end mills cut with both end and side edges, performing both face and peripheral milling. Capable of plunging vertically or cutting laterally, they handle complex contours, curves, holes, and slots.

Tool: End mills with cutting edges on end and sides.

Applications: Complex geometries including profiles, curved surfaces, holes, and slots.

Specialized thread mills with multiple cutting edges produce precise internal and external threads through rotational and helical feed motions, renowned for accuracy and surface finish.

Tool: Multi-edge thread mills capable of complete thread formation.

Applications: High-precision threading across materials and sizes, including complex designs.

This side-wall machining method typically uses end mills to create 90° vertical surfaces like steps and shoulders.

Tool: End mills.

Applications: Machining perpendicular side surfaces and right-angled features.

Employing side or end mills, this removes thin material layers from workpiece edges to create flat or contoured side surfaces.

Tool: Side mills or end mills.

Applications: Edge finishing and thin-layer material removal.

Multi-edge ball-nose tools follow complex contours across multiple axes, often requiring CNC control for intricate 3D surfaces like molds and dies.

Tool: Multi-edge ball-nose cutters.

Applications: Complex contours and detailed surfaces in mold-making and precision components.

Using large, thin circular blades with numerous teeth, this rapid "slitting" process creates narrow kerfs through straight or surface-following cuts.

Tool: Thin circular saw blades.

Applications: Creating narrow slots and separation cuts.

Computer-controlled machining converts CAD models into toolpaths, enabling automated production of complex geometries beyond manual capabilities.

Tool: Computer-controlled tooling.

Applications: High-precision automated machining of intricate components.

Specialized gear cutters or hobs machine gear teeth, with simple gears done manually while complex versions require CNC equipment.

Tool: Gear hobs or form cutters.

Applications: Manufacturing spur, helical, and bevel gears.

Producing beveled edges and angular features requires tapered mills or adjustable-angle tools mounted on tilted spindles or multi-axis machines.

Tool: Tapered mills or angle-adjustable cutters.

Applications: Chamfers, angular grooves, and beveled edges.

Special profile cutters or general tools create detailed surface contours, widely used in automotive, aerospace, and toolmaking industries, typically with CNC machines.

Tool: Custom-profile or general-purpose cutters.

Applications: Detailed surface contours in precision manufacturing.

Two cutters mounted on one arbor simultaneously machine parallel surfaces, slots, or grooves, doubling productivity for features like opposing keyways.

Tool: Parallel-mounted dual cutters.

Applications: Parallel surface machining and opposing feature creation.

Basic horizontal cutters produce flat, rectangular features through straightforward material removal.

Tool: Horizontal slab mills.

Applications: Simple flat surface and step machining.

Multiple cutters on one arbor simultaneously machine different surfaces, optimizing mass production efficiency despite higher setup complexity.

Tool: Multi-tool arbors.

Applications: High-volume production of identical components.

Milling serves virtually all manufacturing sectors, including:

• Aerospace: Engine components, airframes, landing gear
• Automotive: Engine blocks, cylinder heads, crankshafts
• Tooling: Injection molds, die casts, stamping dies
• Medical: Joint replacements, dental implants, surgical tools
• Electronics: Components, circuit boards, enclosures

Emerging milling technologies include:

• High-speed milling: Increased cutting velocities for efficiency and finish quality
• 5-axis milling: Enhanced geometric capabilities through multi-axis coordination
• Smart milling: Sensor and AI integration for process optimization
• Sustainable milling: Eco-friendly coolants and tool materials

As a manufacturing cornerstone, milling continues evolving through technological advancements that expand its precision, efficiency, and environmental sustainability, ensuring its enduring role in industrial production.