Machining: Fundamentals and Processes

Machining inquiries often treat it as a single process, but the term actually bundles seven distinct processes under DIN 8589, each with its own cost structure, from turning to milling to grinding. That range is exactly why two quotes for the same steel bracket, one costed as milled, the other as turned, can land almost 30 percent apart.

In brief: Machining covers manufacturing processes where a tool deliberately removes material from a workpiece to create the desired shape. DIN 8589 distinguishes, among others, turning, milling, drilling, grinding, planing, broaching, and sawing. Which process fits depends on part geometry, material, and required tolerance, there's no blanket rule for cost or precision.

What Is Machining?

Machining is the umbrella term for manufacturing processes in which a tool removes material from a workpiece in the form of chips. This continues until the desired geometry is reached. The material is removed, not reshaped or cast into a mold.

Under DIN 8580, machining belongs to the main group "separating" (Trennen)) within manufacturing processes. Within that group, the standard distinguishes two types of cutting edge. Processes with a geometrically defined cutting edge have a precisely known edge shape, as in turning or milling. Processes with a geometrically undefined cutting edge, such as grinding, rely on many individual abrasive grains that take part in material removal irregularly.

What Machining Processes Exist?

Machining includes turning, milling, drilling, planing, broaching, and sawing, plus grinding as a process with a geometrically undefined cutting edge. DIN 8589 breaks down machining with a geometrically defined cutting edge into these distinct processes. They differ mainly in how the tool and workpiece move relative to each other:

Many parts combine several of these processes in practice. <!-- [PERSONAL EXPERIENCE] --> In our sourcing projects, we regularly see parts that are first sawn, then turned, then drilled, before a single quality check decides on the finished part. For buyers, what ultimately matters isn't the individual process, but whether the combination of all steps reliably holds the required tolerance.

What Sets Cutting Speed, Feed, and Depth of Cut Apart?

Together, these three machining parameters determine how fast material is removed and what the resulting surface looks like.

Cutting speed describes how fast the cutting edge moves relative to the workpiece surface, measured in meters per minute. Feed describes how far the tool and workpiece move relative to each other per revolution or per cutting edge. Depth of cut describes how deep the tool engages the material per pass.

A higher feed removes material faster but leaves a rougher surface and raises cutting forces. A higher cutting speed shortens machining time but wears the tool noticeably faster.

Under Taylor's tool-life equation, tool life falls off disproportionately as cutting speed rises). Even a moderate increase in speed can shorten tool life substantially as a result.

Which Materials Machine Well?

Aluminum and brass machine best, followed by structural steel, while stainless steel places higher demands on tooling and process parameters due to its lower thermal conductivity. How well a material machines is called machinability. DIN 6583 defines it as a material's ability to be machined under given conditions. It's assessed through criteria including tool life, tool wear, cutting forces, surface quality achieved, and chip form:

What Tolerances and Surface Finishes Are Achievable with Machining?

Machining reaches noticeably tighter tolerances than casting or injection molding, because the tool generates the final geometry directly instead of forming it through a mold. The breakdown below by operation type comes from Strobel Industry:

For tightly toleranced fits like bearing seats or shaft connections, machining follows standardized tolerance classes. The H7 fit, for example, sets the standard for many bores. Where a part's overall form or location matters alongside individual dimensions, geometric tolerances come into play. These need to be called out separately on the drawing.

There's no single standardized comparison table between machining and casting processes. In practice, though, tolerances achievable through machining are consistently tighter than those of most casting and injection-molding processes.

What Sets Machining Apart from Forming?

Machining deliberately removes material, while forming reshapes the same material into a new shape without losing mass.

Forming processes like deep drawing or forging make use of the material's grain flow and can selectively increase strength in specific areas. They typically require expensive tooling, though, and only pay off at larger volumes. Machining needs no part-specific tool shape, making it economical even for small and medium batch sizes while offering more geometric freedom. Machining gives up that strength gain in return.

How Is Germany's Machining Industry Developing?

Germany's machining technology sector is currently working through a period of consolidation after several weaker years.

According to VDMA Precision Tools, the sector's production value fell around 9 percent in 2024 to roughly €9 billion. A further decline of around 7 percent to roughly €8.5 billion followed in 2025. The association expects a gradual stabilization for 2026. Association chairman Stefan Zecha described the situation by saying the industry had three difficult years behind it. The low point, he said, appeared to have been reached.

What Should Buyers Check Before Sourcing Machined Parts?

Anyone sourcing machined parts should spell out four points clearly in the machining inquiry:

• the required tolerance class

• the material, including its condition

• the necessary surface finish

• the intended inspection method

If any of these is missing, the manufacturer calculates on its own assumptions. That can lead to renegotiation or deviations at incoming goods inspection later. For threaded holes, thread tolerances should also be called out separately on the drawing. Otherwise, they're often designed to the manufacturer's default rather than the customer's requirement.

Frequently Asked Questions

What's the difference between turning and milling?

In turning, the workpiece rotates while the tool moves. In milling it's the reverse: the multi-edge tool rotates while the workpiece mostly stays fixed, or is only repositioned between machining steps.

How is a material's machinability determined?

It's assessed against five criteria: tool life, tool wear, cutting forces involved, surface quality achieved, and the shape of the resulting chips.

Which materials machine best?

Aluminum and brass are considered particularly machinable, and structural steel is also straightforward. Stainless steel places higher demands on tooling and process parameters due to its lower thermal conductivity.

Can every part be machined?

Most metals and many technical plastics can be machined. Very complex internal geometries or extremely thin walls, though, push machining against mechanical limits that other processes, such as casting, handle better.

Conclusion: Machining as the Foundation for Precise Parts

Machining remains one of the most versatile manufacturing processes because it combines tight tolerances, geometric freedom, and economic viability even at smaller batch sizes. Knowing the core DIN 8589 processes, the relevant material properties, and the achievable tolerances lets buyers judge manufacturing quotes realistically. It also makes writing precise technical inquiries easier.

Line Up supports buyers through exactly this step: the technical specification, selecting suitable manufacturing partners in the Far East, and quality assurance on the finished machined part. 👉 Schedule a no-obligation consultation and find out which machining process makes the most economic sense for your next project.