Routing Methods in Woodworking

You can’t make an omelet without breaking eggs— and the same goes for the “successor” to the classic plane: today’s computer-controlled milling machine. With modern milling tools, you can perform a wide variety of machining operations that allow for flexible, precise, and high-quality woodworking.

What are milling processes and which method is best suited for your purpose? In this article, we'll explain which milling processes help you achieve quality results and give you an overview of milling techniques in woodworking. You'll also learn the advantages and disadvantages of each milling process and what you should consider before choosing one.

Table of Contents

• Definition
• Overview of Milling Processes
• Classification
• Routing Methods in Woodworking
• Milling Processes by Direction of Cut
• How do Milling Processes Differ?
• Milling Processes – Pros and Cons
• FAQ

Definition: What are Milling Processes?

“Milling process” refers to a machining technology where material is removed from the workpiece by the circular motion of a milling cutter. You can use it to process wood, metal, and plastic. In woodworking, milling tools are used in furniture and interior design or window construction to achieve functional and decorative effects with the help of special milling inserts. Only a targeted selection of milling processes and milling inserts ensures you get a quality result.

Overview: What Milling Processes Are There?

The milling process you choose depends on your project's requirements. You can machine workpieces on milling machines using these methods:

• CNC Routing
• Profile Milling
• Form Milling
• Circular Milling
• 3D Milling
• Face Milling
• Joint Milling (Tongue, slot and Groove, Counter Profile)

Tip: The RUWI router table (a mobile table milling machine) offers you a semi-stationary system that combines precise milling work on a stable work table with great flexibility.

Precise milling on the RUWI router table

How are milling processes categorized?

Material, intended use, and shape all play a role when machining a workpiece. These parameters help you find the right milling process.

Simple, cylindrical, and flat surfaces:

• Face milling for flat surfaces and steps, with a straight-line feed
• Cylindrical milling for cylindrical surfaces (e.g., round tenons, internal or external curves)

Milling profiles:

• Profile milling with a special profile milling tool that gives your workpiece a contour in a single pass

Curved surfaces, especially in mold making:

• Form milling using controlled feed movement for complex, spatial structures (e.g., NC form milling, copy milling)

Highly productive and efficient:

• CNC milling, 3D milling are fast, versatile, and precise, especially for complex shapes or series production parts

Overview: Milling Processes in Woodworking

When you're using milling machines in wood processing, you expect efficient and precise results. Each milling process is designed for specific machining operations to produce workpieces cost-effectively.

CNC Routing

These are computer-controlled milling machines with high-speed spindles and plenty of tool stations. They're great for furniture making or other woodworking shops that benefit from their versatility and speed.

Circular Milling

With special cutter heads, you can create round tenons or cylindrical shapes. You can also use them to clean up round saw cutouts.

Form Milling

Form milling is suitable for complex, three-dimensional designs or profiling. It's usually done on CNC machines to achieve high precision.

Joint Milling

Wood joints are also created by milling: dovetail and tongue-and-groove cutters for corner joints on drawers, slot- and tongue-and-groove profiles for shelves and back panels, as well as counter-profile sets for framed doors. It is crucial that the profile and counter-profile be purchased as a matched set and resharpened together—otherwise, they will no longer fit together properly later on.

Face Milling

In face milling, an uneven surface is removed in overlapping passes until it is flat. In woodworking, this is the method used for workpieces that do not fit through a planer or thicknesser—because they are too wide, too irregular, or not quite rectangular.

Profile Milling

Many decorative milling operations in the furniture industry are performed using profile cutters. Curves, slots other decorative elements on moldings and cabinet fronts are typical applications. Typical radii range from 4 to 18 mm.

3D Milling

Nowadays, 3D milling is affordable even for small businesses. It allows for an extensive variety of shapes and automated processes, especially with form milling. You can use it to realize even unusual customer requests.

Milling Processes by Direction of Cut

The milling direction is determined by the relationship between the feed direction and the direction of rotation of the tool. It is not the same as the grain direction of the wood—both influence the result, but independently of one another. A distinction is made between:

Climb Milling

The cutting edge moves toward the feed at the point of contact. The chip starts at zero and becomes thicker toward the exit; the friction phase at the start of the cut generates heat and reduces tool life. In return, the cutting force acts against your feed direction, and the workpiece remains controllable. With manual feed, this is the direction of operation.

Conventional Milling

The direction of rotation of the cutter and the feed direction are the same; the cutting force acts in the direction of feed. The tool pulls the workpiece toward itself. This self-feed cannot be controlled during manual feeding—regardless of the operator’s experience. The article “Synchronous Milling” explains when and under what conditions synchronous milling is permissible.

Milling operation on the RUWI router table

How do Milling Processes Differ?

Each milling process is optimized for a specific application: Whether you want to create profiles, steps, surfaces, or wood joints, each process uses different milling heads and settings. The key factors are tool shape, depth of cut, rotational speed, and feed rate—and, for manually fed machines, the feed direction. When combined with CNC systems, these processes enable highly precise and versatile machining operations.

Milling Processes – Pros and Cons

When selecting a milling process, you're looking for the optimal balance between cost-effectiveness and machining quality. Unlike metalworking, wood milling doesn't use liquid cooling. This is crucial for hardwoods to prevent the tool or workpiece from overheating and getting damaged. So, make sure you have a coordinated combination of feed rate, spindle speed, and cutter diameter.

Synchronous or counter-rotation is not a matter of experience, but of the feed method: With manual feed, the cutter rotates in the opposite direction to the workpiece. This places greater stress on the cutter and the workpiece because the chip becomes thicker as it exits, and the edge at the chip exit is more prone to tearing. On a manually fed machine, the key factors for surface quality are, in any case, the sharpness of the cutting edge, the distribution of the depth of cut, and a uniform feed rate.

FAQ

How are milling processes classified?

Classification is typically based on:

1. Type of material processing (e.g., face milling, peripheral milling)
2. Feed rate and direction (conventional milling, climb milling)

Milling processes are also often classified by milling machines, milling tools, and materials.

What milling processes are there?

The most common processes include: CNC milling, profile milling, form milling, cylindrical milling, 3D milling, face milling, and joint milling.