A Guide to Metal Machining Processes

Metal machining is an essential manufacturing practice made up of various different processes, enabling the creation of precise parts from raw metal stock. Whether it’s a simple hole or a complex 3D profile, machining transforms materials into components that power everything from airplanes and automobiles to electronics and industrial systems.

But not all machining methods are created equal. With so many available techniques—each suited to different materials, tolerances, and production goals—it can be challenging to know which process is best for your needs.

This guide breaks down the most common types of metal machining processes, including both conventional and non-conventional methods, as well as CNC machining and process selection tips. Whether you’re new to machining or looking to refine your manufacturing strategy, this overview will help you make informed, cost-effective decisions for your next project.

Conventional Metal Machining Processes

Conventional metal machining techniques use mechanical cutting tools to remove material from a metal workpiece. These time-tested methods are ideal for producing parts with high precision and tight tolerances, especially in low to medium production volumes.

Turning

Turning is performed on a lathe, where the metal workpiece spins while a single-point cutting tool moves along its surface to remove material. This method is ideal for shaping cylindrical parts such as shafts, bushings, rods, and threaded components. Turning allows for tight dimensional control and smooth finishes, especially in high-speed or high-volume production settings.

Milling

Milling involves a rotating multi-point cutting tool that moves across a stationary workpiece to remove material. It’s one of the most flexible machining processes, used to create slots, pockets, holes, and intricate 3D shapes. With vertical and horizontal milling capabilities, it’s suitable for a wide range of part geometries, including flat surfaces and complex contours.

Drilling

Drilling uses a rotating drill bit to produce round holes in metal, typically as a starting point for fasteners, rivets, or additional machining operations like tapping or countersinking. Drilling can be done with manual or CNC-controlled machines and is essential for everything from simple assembly holes to precision-aligned bores in structural components.

Grinding

Grinding removes material using a rotating abrasive wheel and is primarily used for finishing surfaces with a high degree of precision. It’s commonly applied to hardened metals where other machining tools would wear out quickly. Grinding ensures tight tolerances, smooth finishes, and excellent flatness—making it ideal for high-performance parts in aerospace, automotive, and tooling applications.

Non-Conventional Metal Machining Processes

Non-conventional machining processes use methods other than direct mechanical cutting to shape metal. These are ideal for hard-to-machine materials, intricate shapes, or when thermal or electrical energy is needed for precision.

Electrical Discharge Machining (EDM)

EDM removes metal using controlled electrical sparks that generate intense heat to erode material from the workpiece. Since it doesn’t involve direct contact, it’s ideal for very hard materials or parts that are difficult to machine mechanically. This process is commonly used in tool and die manufacturing, producing sharp corners, narrow slots, and intricate internal cavities with high accuracy. It works best with conductive metals like steel, titanium, and carbide.

Laser Cutting

Laser cutting uses a focused, high-powered laser beam to melt, burn, or vaporize material along a precise path. This method delivers tight tolerances, clean edges, and minimal kerf, making it excellent for cutting thin sheets, engraving, or producing complex patterns with minimal material waste. Laser cutting is fast, efficient, and ideal for applications in aerospace, signage, electronics, and prototyping.

Waterjet Cutting

Waterjet cutting uses a high-pressure jet of water, sometimes mixed with abrasive materials like garnet, to cut through metal without heat. This cold-cutting process prevents thermal distortion, making it perfect for heat-sensitive metals such as aluminum, stainless steel, and titanium. It’s highly versatile, capable of cutting thick or layered materials with excellent edge quality, and is commonly used in aerospace, architecture, and heavy industry.

Ultrasonic Machining

Ultrasonic machining uses high-frequency vibrations combined with an abrasive slurry to remove material from the workpiece. This non-thermal, non-chemical method is well-suited for brittle or delicate metals and allows for machining of fine holes, sharp edges, and hard-to-reach features without introducing stress or heat. It’s ideal for applications requiring precision in fragile materials, such as electronics, aerospace components, and micro-machining.

CNC Machining Process: Precision Through Automation

CNC (Computer Numerical Control) machining is a modern approach to metal fabrication where computers precisely control machining tools based on programmed instructions. It’s used to automate conventional processes like turning, milling, drilling, and even some non-conventional methods such as EDM.

CNC machining offers several key advantages:

High accuracy and repeatability
Faster production with reduced human error
Efficient production of complex or custom parts

CNC is ideal for both prototyping and high-volume manufacturing across industries like aerospace, automotive, and medical devices. It enables tighter tolerances, smoother finishes, and quicker turnaround times—especially for complex geometries.

How to Choose the Right Machining Process for Your Project

Selecting the right metal machining process depends on several key factors—each of which can impact the efficiency, precision, and cost of your final part. Here’s what to consider when deciding which method is best for your application.

1. Material Type

Different metals respond better to specific processes.

Aluminum and brass are easy to machine and suitable for milling, turning, or CNC.
Hardened steels or exotic alloys may require EDM or grinding for accuracy without tool damage.

2. Part Geometry and Tolerance Requirements

Complex shapes, internal features, or tight tolerances may require precision techniques like CNC milling, EDM, or grinding. Simpler parts can often be produced efficiently with conventional methods.

3. Surface Finish Needs

If your part requires a smooth finish or fine detail (e.g., medical or aerospace components), you may need grinding, polishing, or post-machining treatments to achieve the desired surface quality.

4. Volume and Production Speed

Low-volume or prototype runs may benefit from flexible CNC machining, while high-volume production might call for streamlined, conventional setups or automation to reduce per-part costs.

5. Budget Constraints

Some processes, like EDM or laser cutting, offer precision but come with higher costs. Choosing the right balance between quality and efficiency is key to staying within budget.

Consulting with a machining expert, like the team at PMF, ensures your process choice aligns with performance goals and manufacturing timelines.

Why Choose PMF for Metal Machining Services

At PMF, we combine advanced machining processes with decades of hands-on expertise to deliver precision-machined metal parts that meet the most demanding requirements. Whether you’re producing a single prototype or scaling up for mass production, our team is equipped to guide your project from concept to completion.