Types of Machining: A Practical Guide to Every Process and When to Use Each One

Most guides to types of machining read like a glossary. They will list 20+ processes, give a one-sentence description of each, and leave you still wondering which one your part really needs. That’s not useful if you’re writing an RFQ or evaluating CNC suppliers in China.

Here’s what actually matters: there are roughly 12 machining processes that cover 95% of custom parts production. The rest are niche. This guide covers all of them - but more importantly, it tells you what tolerances each process achieves, what materials it works with, and when to pick one over another.

TL;DR / Key Takeaways

• Machining processes split into 2 categories: conventional (physical cutting tools) and non-conventional (energy-based material removal like EDM, laser, and waterjet)
• The 3 most common processes - turning, milling, and drilling - handle the majority of custom parts production
• Tolerance ranges vary dramatically: CNC milling holds ±0.025 mm (IT7-IT8 grade), while laser cutting typically manages ±0.1 mm
• CNC is not a machining process, but a method of automation for turning, milling, drilling, etc.
• Your process choice depends on 4 factors: part geometry, material, required tolerance, and production volume

What Is Machining?

Machining is a subtractive manufacturing process - you start with a block of material and remove everything that isn’t the final part. That’s what separates it from additive processes like 3D printing (which builds up) and forming processes like casting or stamping (which reshape).

Each machining process employs a particular type of energy to perform a material removal operation. Conventional processes use a physical cutting tool. Non-conventional processes use electrical discharge, chemical reactions, lasers, or high-pressure water instead.

The distinction matters for sourcing. Conventional machining is widely available - most factories with a CNC mill or lathe can handle it. Non-conventional processes like wire EDM or laser machining require specialised equipment and fewer factories offer them. When we audited verified CNC factories in China, 38.8% operated 5-axis milling equipment, but wire EDM and specialised processes were significantly less common.

What Are the Main Categories of Machining?

Machining processes split into 2 primary categories based on how they remove material:

Category	How It Works	Examples	Best For
Conventional	A physical cutting tool contacts the workpiece	Turning, milling, drilling, grinding, broaching	Most custom parts; widely available, cost-effective
Non-conventional	Energy (electrical, chemical, thermal, or kinetic) removes material without tool contact	EDM, laser, waterjet, chemical machining, ECM	Hard materials, complex geometries, delicate features

The majority of custom manufactured parts are made using conventional methods. Non-conventional manufacturing methods exist to fill the gap when the material is too hard to cut, the geometry is too complex for a physical cutting tool, or when features are too small for a cutting tool.

What Are the Conventional Machining Processes?

Conventional machining processes are the workhorses of manufacturing. They all involve a cutting tool physically removing material from a workpiece.

Turning

Turning rotates the workpiece on a lathe while a stationary cutting tool removes material. It’s the go-to process for cylindrical parts - shafts, bushings, pins, and any component with rotational symmetry.

CNC lathes handle turning at IT8-IT7 tolerance grades for standard work (roughly ±0.025 mm) and IT5-IT7 for precision applications with surface roughness of Ra 1.6–0.8 µm. It’s one of the most cost-effective machining processes because material removal rates are high and setup is relatively quick.

Best for: Cylindrical and conical parts, threads, grooves, and tapered surfaces. See our guide to CNC turning services for what’s achievable at scale.

Milling

Milling uses a rotating multi-tooth cutting tool that moves against a stationary (or slow-moving) workpiece. It’s the most versatile machining process - 3-axis mills handle flat surfaces, slots, and pockets, while 5-axis machines produce complex freeform geometries in a single setup.

Standard CNC milling achieves IT8-IT7 tolerance (±0.025 mm), with fine milling reaching IT7-IT6 and surface roughness of Ra 0.63–1.6 µm. 5-axis milling reduces the need for multiple setups, which cuts both cost and cumulative tolerance error.

Best for: Flat surfaces, complex 3D shapes, pockets, slots, and parts requiring features on multiple faces.

Drilling

Drilling creates circular holes using a rotating drill bit. It sounds simple, but it accounts for a huge proportion of machining operations - nearly every custom part has at least one hole.

Standard drilling achieves IT10-IT11 tolerance. For tighter holes, you follow up with boring (to enlarge and true up the hole) or reaming (IT7-IT8, achieving precise diameter and smooth finish).

Best for: Holes of any size. Often combined with tapping to add threads.

Grinding

Grinding uses an abrasive wheel to remove very small amounts of material, achieving surface finishes and tolerances that cutting tools can’t match. It’s typically a finishing operation - you rough the part with milling or turning, then grind it to final spec.

According to international tolerance grade references, grinding achieves IT8-IT5 or better, with surface roughness from Ra 1.25 µm down to Ra 0.01 µm for mirror grinding. Cylindrical grinding handles round parts, while centreless grinding processes high volumes of small cylindrical components without fixturing.

Best for: Tight-tolerance finishing, hardened materials (post heat treatment), and achieving fine surface finishes.

Boring

Boring enlarges an existing hole to a precise diameter. Where drilling creates the initial hole, boring refines it - correcting roundness, straightness, and diameter to tighter tolerances than drilling alone can achieve.

Best for: Precision holes, engine cylinders, and any application where hole diameter accuracy matters more than drilling can deliver.

Broaching

Broaching pushes or pulls a toothed tool through a workpiece in a single pass, cutting a complex profile all at once. It’s fast and accurate (IT7 achievable) - but the tooling is expensive, so it only makes economic sense at higher volumes.

Best for: Internal keyways, splines, non-circular holes, and gear teeth at medium-to-high volumes.

Sawing

Sawing cuts material to length or separates sections. It’s typically a first-step operation before further machining. Band saws handle most work, while abrasive saws cut harder materials.

Best for: Cutting bar stock, tube, and plate to rough size before precision machining.

Other Conventional Processes

Several more specialised conventional processes handle specific operations:

• Planing/shaping - creates flat surfaces using a single-point tool; largely replaced by CNC milling in modern production
• Reaming - finishes drilled holes to precise diameter (IT7-IT8 tolerance)
• Tapping - cuts internal threads into existing holes
• Honing - improves surface finish and geometry of bored holes (achieves Ra 0.4–0.1 µm)
• Lapping - ultra-fine finishing process for flatness and surface finish (Ra below 0.05 µm)

What Are the Non-Conventional Machining Processes?

Non-conventional processes remove material using energy rather than a physical cutting tool. They handle situations where conventional machining can’t - extremely hard materials, micro-scale features, or geometries that no tool can physically reach.

Electrical Discharge Machining (EDM)

EDM removes material using controlled electrical sparks between an electrode and the workpiece. It only works on conductive materials, but it machines hardened steel, tungsten carbide, and titanium alloys that would destroy conventional cutting tools.

Two main types exist:

• Sinker EDM - uses a shaped electrode to “burn” a cavity into the workpiece (IT7-IT8 tolerance). Used for injection mold cavities, complex dies, and blind features.
• Wire EDM - uses a thin wire electrode (0.1–0.3 mm diameter) to cut through the workpiece like a saw. With skim cuts, achieves ±0.005 mm typical tolerance and surface finish Ra 0.2–1.6 µm. Used for precision profiles, extrusion dies, and small gears. See Haizol’s wire EDM services for tolerance specs.

Best for: Hardened metals, complex internal features, precision molds and dies, thin-walled parts that can’t withstand cutting forces.

Laser Beam Machining

Laser machining uses a focused beam of light to melt, vaporise, or ablate material. CNC laser cutting handles sheet metal at high speed, while laser drilling creates micro-holes in aerospace components.

Standard CNC laser cutting achieves IT8-IT16 tolerance depending on material thickness, with minimal heat-affected zone on thin materials. It’s fast and requires no physical tool wear.

Best for: Sheet metal cutting, micro-drilling, engraving, and materials that are difficult to machine conventionally.

Waterjet Machining

Waterjet cutting uses a high-pressure stream of water (or water with abrasive particles) to cut through virtually any material - metal, stone, glass, composites, and food. It produces no heat-affected zone, which matters for heat-sensitive materials and aerospace alloys.

Abrasive waterjet achieves approximately ±0.1 mm tolerance on most materials.

Best for: Heat-sensitive materials, composites, thick plate, and applications where thermal distortion is unacceptable.

Chemical and Electrochemical Machining

Chemical machining (CHM) dissolves material using controlled chemical reactions. Electrochemical machining (ECM) uses an electrolyte solution and electrical current to remove material. Both processes produce no mechanical stress and no heat-affected zone.

Best for: Deburring, removing thin layers of material uniformly, and machining parts where mechanical stress would cause distortion.

Ultrasonic Machining

Ultrasonic machining uses high-frequency vibrations to drive abrasive particles against the workpiece, removing material through micro-chipping. It’s one of the few processes that can machine brittle, non-conductive materials like ceramics and glass without cracking them.

Best for: Ceramics, glass, silicon, gemstones, and other hard, brittle materials.

How Do Conventional and Non-Conventional Machining Compare?

Conventional and non-conventional machining differ fundamentally in how they remove material - and that difference drives cost, capability, and factory availability.

Factor	Conventional Machining	Non-Conventional Machining
Material removal	Physical cutting tool	Energy-based (electrical, thermal, chemical, kinetic)
Material range	Most metals and plastics	Includes hardened steel, ceramics, composites, glass
Achievable tolerance	IT5–IT11 depending on process	IT6–IT13 depending on process
Surface finish	Ra 0.4–3.2 µm typical; Ra 0.05 µm with lapping	Ra 0.2–6.3 µm depending on process
Material removal rate	High - fast for bulk removal	Low to moderate - slower per volume
Tooling cost	Lower - standard inserts and end mills	Higher - electrodes, specialised equipment
Factory availability	Widely available	Requires specialised equipment; fewer factories
Relative cost	$ to $$	$$ to $$$$

The practical takeaway: start with conventional machining and only move to non-conventional when the material, geometry, or tolerance demands it.

How Does CNC Fit into Machining?

CNC (Computer Numerical Control) isn’t a machining type - it’s an automation method. A CNC controller reads G-code instructions and precisely moves the cutting tool (or workpiece) along programmed paths. It can control turning, milling, drilling, grinding, EDM, laser cutting, and more.

Why it matters: CNC transformed machining from an operator-dependent craft into a repeatable, programmable process. A skilled machinist can hold ±0.05 mm on a manual mill. A properly programmed CNC mill holds ±0.025 mm all day, every day, across 1,000 parts.

CNC Machine Type	Based On	Axes	Typical Tolerance	Best For
CNC lathe	Turning	2–4	±0.025 mm	Cylindrical parts, shafts, fittings
CNC mill (3-axis)	Milling	3	±0.025 mm	Flat parts, pockets, simple 3D shapes
CNC mill (5-axis)	Milling	5	±0.01 mm	Complex freeform surfaces, aerospace parts
Swiss-type CNC	Turning + milling	5–7	±0.005 mm	Small precision parts, medical devices, watch components
CNC EDM (wire)	EDM	2–5	±0.002 mm	Precision profiles, dies, micro-parts
CNC laser	Laser cutting	2–3	±0.1 mm	Sheet metal cutting, engraving

Sidenote. When you see “5-axis CNC machining” in a factory profile, it means their mill can approach the workpiece from virtually any angle in a single setup. This matters for complex parts because it eliminates the tolerance stack-up that comes from refixturing between operations. In our 2026 audit of Chinese CNC factories, 38.8% operated 5-axis equipment from brands like DMG MORI, Mazak, and Makino.

Which Machining Process Should You Choose?

Choosing the right process comes down to 4 factors. Here’s the decision logic:

1. Part geometry - Cylindrical? Start with turning. Flat surfaces or complex 3D? Milling. Internal keyways? Broaching. Thin sheet? Laser or waterjet cutting. Need help matching process to part? Our guide on choosing the right process for small metal parts breaks this down further.

2. Material - Standard metals (aluminium 6061, steel, brass) work with any conventional process. Hardened steel above 50 HRC? EDM or grinding. Ceramics or glass? Ultrasonic machining. Composites? Waterjet avoids delamination.

3. Required tolerance - General commercial parts (±0.1 mm) work with basic drilling, sawing, or laser cutting. Standard precision (±0.025 mm) needs CNC turning or milling. Tight precision (±0.005 mm or better) requires grinding, wire EDM, or Swiss machining. Tolerances follow the ISO 2768 general tolerance standard in four classes: fine (f), medium (m), coarse (c), and very coarse (v).

4. Production volume - Prototype or low-volume (1–50 parts)? CNC milling or turning with standard tooling. Medium volume (50–5,000)? Same processes, possibly with fixtures for faster changeover. High volume (5,000+)? Consider broaching, Swiss machining, or multi-spindle lathes where the tooling investment pays off.

Machining Process Comparison Table

Process	IT Grade	Typical Tolerance	Surface Finish (Ra)	Materials	Relative Cost	Best Volume
Turning (CNC)	IT7–IT8	±0.025 mm	0.8–1.6 µm	Most metals, plastics	$	Any
Milling (CNC 3-axis)	IT7–IT8	±0.025 mm	0.63–1.6 µm	Most metals, plastics	$	Any
Milling (CNC 5-axis)	IT6–IT7	±0.01 mm	0.4–1.6 µm	Most metals, plastics	$$	Low–medium
Drilling	IT10–IT11	±0.1 mm	1.6–6.3 µm	Most metals, plastics	$	Any
Grinding	IT5–IT6	±0.005 mm	0.05–0.4 µm	Metals (inc. hardened)	$$	Medium–high
Broaching	IT6–IT7	±0.025 mm	0.8–1.6 µm	Most metals	$$$ (tooling)	High
Swiss machining	IT5–IT6	±0.005 mm	0.2–0.8 µm	Most metals	$$	Medium–high
Sinker EDM	IT7–IT8	±0.005 mm	0.4–6.3 µm	Conductive metals only	$$$	Low–medium
Wire EDM	IT6–IT7	±0.005 mm	0.2–1.6 µm	Conductive metals only	$$$	Low–medium
Laser cutting	IT8–IT16	±0.1 mm	1.6–6.3 µm	Sheet metal, thin plate	$	Any
Waterjet	IT10–IT12	±0.1 mm	3.2–6.3 µm	Any (inc. composites, glass)	$$	Any
Ultrasonic	IT7–IT8	±0.01 mm	0.4–1.6 µm	Ceramics, glass, brittle materials	$$$$	Low

Sidenote. These are typical values for competent factories. Actual tolerances depend on part size, geometry complexity, and the specific machine. When in doubt, specify your tolerances on the drawing and let the factory confirm what’s achievable.

Frequently Asked Questions

What are the 3 most common machining processes?

The 3 most common machining processes are turning, milling, and drilling. Together they handle the vast majority of custom parts production. Turning creates cylindrical parts on a lathe, milling creates flat and complex 3D shapes with a rotating cutter, and drilling creates holes. Most CNC machine shops offer all 3.

What are the 7 basic types of machine tools?

The 7 basic machine tools are: Lathe or Turning Machine, Milling Machine, Drill Press Machine, Grinder Machine, Saw Machine, Broaching Machine, and Planer/Shaper Machine. This classification is based upon the primary machining operations. This classification has been used for many decades in manufacturing engineering. The latest computer-controlled versions of these machines are used today for production work. However, the principles of machining have not changed.

What is the difference between conventional and non-conventional machining?

In conventional machining, material is removed with the help of a physical cutting tool. Non-conventional machining involves removing material with the help of an energy source such as electrical sparks (Electrical Discharge Machining), light (Laser Machining), chemical reactions (Chemical Machining), or high pressure water jets (Water Jet Machining).

What is the difference between CNC machining and manual machining?

In computer numerical control machining, computer-controlled motors drive the cutting tool. The cutting tool is moved in a path to machine the workpiece. The accuracy of the machine is ±0.025mm. In manual machining, the machine is operated by the skill of the operator. The accuracy of the machine is ±0.05mm.

What materials can be machined?

Most engineering materials can be machined: aluminium alloys (6061, 7075), carbon steel, stainless steel (304, 316), tool steel, titanium, brass, copper, engineering plastics (Delrin, nylon, PEEK), and composites. The machining process determines the material range - conventional processes handle metals and plastics, while EDM works only on conductive materials, and waterjet cuts virtually anything including glass and stone.

How do I choose a machining process for my part?

Start with your part’s geometry (cylindrical = turning, complex 3D = milling), then check material compatibility, required tolerance, and production volume. For most custom metal parts, CNC milling or turning with standard tooling covers the job. Move to specialised processes (EDM, grinding, waterjet) only when the geometry, material, or tolerance demands it.

Get Quotes for Any Machining Process

If you know what process your part needs - or even if you don’t - the fastest way to get real pricing is to submit your CAD files with material and tolerance specs. Haizol routes your RFQ to capability-matched, verified factories across CNC machining, EDM, grinding, sheet metal, and more. 90% of RFQs receive quotes from 8+ verified factories within 24 hours for side-by-side comparison.