Milling a groove in wood with the router - how it works

Milling grooves in wood is an important skill for any ambitious woodworker. Grooves make it possible to fit parts together and join them precisely. You can cut such grooves quickly and cleanly into wood with a router. In this guide, we will show you step by step how to do this - from preparation and the materials and tools required to valuable tips for perfect results.

Milling grooves on the RUWI milling table

Table of contents

• The most important facts at a glance
• Definition: What is a groove?
• How can I mill a groove?
• Preparation: What do I need for groove milling?
• Instructions: Milling a groove in wood
• Which machines and tools for slot milling?

The most important facts at a glance

1. Preparation: Define the groove according to function, shape and purpose.
2. Tool selection: Choose the right tool based on size, position and material.
3. Safety: Always observe the safety measures when setting up the milling machine and when milling.

Definition: What is a groove?

Groove milling is a specialized milling process in which you mill an elongated recess (groove) into the workpiece to fulfill specific functions or requirements. Often, the groove serves to accommodate another component, such as a back panel, a bottom, or a spring. Aesthetic or design considerations also play a role: for example, to make fronts appear slimmer or to visually separate components (V-groove, decorative grooves).

How can I mill a groove?

To mill a specific groove into a wooden surface, you’ll usually need a groove cutter (end mill) and a stop or template that defines the groove’s path. A disc groove cutter (Lamello cutter) is particularly well-suited for routing a groove along a straight or curved edge. For this, you use either a guide ring or a stop as a guide.

Preparation: What do I need for groove milling?

Your workpiece should be non-slip or securely clamped so that it does not shift during milling. The tool you choose (a groove cutter or disc groove cutter) must be suitable for the desired groove profile and the material. You should also ensure compatibility with the machine (shank diameter, speed range). Always use a dust extraction system and personal protective equipment (PPE).

Material list

• Non-slip or anti-tip mat or workbench
• Workpiece to be grooved
• If applicable, a component that is inserted into the groove
• PPE (hearing protection, safety goggles, dust mask)
• Vacuum system or vacuum cleaner

Tools

• Handheld router or router table
• End milling cutter or side milling cutter
• Calipers, tape measure, or folding rule

Instructions: Milling a groove in wood (6 steps)

Here, we’ll walk you through a concise, step-by-step guide on how to mill a groove into a wooden board using a router table and a 12-mm shank groove cutter.

Step 1: Selecting the right milling cutter

Choosing the right router bit is crucial. Select a groove cutter or disc groove cutter that provides the diameter and depth you need. Consider whether you want to create the groove on a flat surface or along an edge. Make sure it is compatible with your machine (shank diameter, maximum speed) and suitable for the material you’ll be routing.

Tool compartment with various groove cutters

Groove cutters in action

Step 2: Set up the milling cutter on the machine

1. Make sure that the router is switched off before you change the cutter.
2. Open the spindle holder (hold the spindle with an open-end wrench, loosen the collet nut or use the spindle lock).
3. Insert the milling cutter into the collet up to the marking (everything should be clean and free of dirt).
4. Tighten the clamping nut firmly and check that the cutter is securely seated.
5. Only then can you switch the router back on.

Shaft-groove cutter ready for clamping

Tightening the collet

Step 3: Adjusting the stop jaws

On a milling table, you can loosen the stop jaws on the fence and position them so that your workpiece is guided without there being too much play. Then slide the entire fence to the correct depth and fix it in place. This prevents the workpiece from tilting or catching.

Secure the positioned stop jaw

Step 4: Adjusting the cutter height

Use a depth gauge or measure the desired groove depth on the workpiece and mark it. Set the milling cutter so that it mills exactly this depth. Always make a test cut to check the settings and adjust them if necessary.

Adjust the cutter depth on the workpiece

Step 5: Milling the groove in wood

Put on a tool cover and connect an extraction system. Wear your PPE (safety goggles, ear protection, dust mask). Keep hands and fingers away from the danger zone. Feed the workpiece along the fence at a steady speed. Too little feed leads to burn marks, too much feed puts a strain on the tool and motor and can cause scoring or tearing. To ensure that the workpiece rests securely, you can attach a hold-down device or an additional wooden strip to the fence jaws.

Tip: It is best to always mill in the opposite direction. Synchronized milling increases the risk of accidents.

Start grooving at the stop ruler

Milling grooves with a constant feed rate

Step 6: Result and conclusion

After the first pass (preferably on a test piece), check the groove for dimensional accuracy and surface quality. If necessary, adjust the settings and mill again. With the right machine, the right tools and a little practice, you can achieve clean and precise groove milling.

Result of the finished groove

A clean groove cut as the final result

What types of machines and tools are available for slot milling?

Machines

• Handheld router: Portable and versatile for a wide range of routing applications.
• Router table: Repeatable precision, more stable guidance, good view of the tool.
• CNC milling machine: Suitable for high-precision and serial grooving work.
• Table router: Stationary and powerful, especially for large workpieces.

Tools

• Disc groove cutters: Various groove widths, some with a guide ring (e.g., Lamello sizes).
• End and slot milling cutters: Various shank and cutter diameters, with two, three or more cutting edges; partly bottom cutting (face ground) or flank cutting.
• T-slot cutter: For screw guides, T-nuts or keyhole suspensions.
• V-groove cutter: For lettering, decorative grooves or joint accentuation.
• Groove cutters with a rounded edge or chamfered cutters: For decorative grooves, drainage channels, juice grooves, handle strips, or handrails.

Tip: Milling cutter sets from different manufacturers are often cheaper than individually purchased milling tools. Pay attention to suitable shank diameters and speed ranges.