Milling a groove in wood – 6-step instructions for the router

Milling grooves in wood is an important skill that every aspiring woodworker should learn. Grooves allow parts to connect by fitting one into the other. With a router, you can cut grooves in wood quickly and precisely. In this guide article we will explain in detail how to cut clean and precise grooves in wood with the router using a 6-step guide. You will learn everything about the preparation and the required materials and tools. In our detailed and illustrated instructions, we show how a groove is milled in wood with the router and also give valuable tips.

The most important facts at a glance

  1. Preparation: Defining the groove according to its function, shape and intended use
  2. Tool selection: Select the appropriate tool based on the size and position of the groove and the material
  3. Safety: Observe the safety measures when setting up the milling machine and milling the groove

Definition: What is a groove

Groove milling is a special milling process in which a groove or indentation is milled into the workpiece to fulfill specific functions or requirements.

A groove is an elongated indentation. This can be straight or curved. A groove is usually sawn or milled for technical / functional reasons. For example, to accommodate other components (cabinet rear panel, drawer bottoms, tongue and groove connections).

A groove can also be used for optical/design reasons. Longitudinal grooves, for example, make a furniture front or wall cladding appear slim or raised. Or to optically separate components from each other. (E.g. a V-groove when gluing the width of a solid wood table, transition from solid wood paneling to the door frame)

How can I mill a groove?

However, if you want to mill a groove in a wooden surface, you need a groove cutter with a shank. A stop or template is therefore used to obtain a defined groove.

A disc groove cutter (lamella cutter) is very well suited to milling a groove on a straight or curved edge. To do this, the milling cutter is usually guided along with the thrust ring or a stop with the edge and then mills the groove there.

Preparation: What do I need to mill a groove?

The material should be non-slip and safe on a surface or be tightened. Then the right tool for the groove and the material should be selected. Important: Tool and machine must match. (Shaft diameter, speed range…). In general, you should use an extraction system / vacuum cleaner and personal protective equipment (PPE) when milling .

material list
Tilting non-slip pad / work table
Workpiece to be grooved
possibly Component that is inserted into the slot
PPE (ear protection, goggles, dust mask..)
1 (hand) router or router table
2 shank grooving cutter or disk grooving cutter
3 calipers / tape measure / folding rule

Procedure: Step-by-step instructions for slot milling

  • Determine which tool is suitable for the desired groove (groove cutter or disc groove cutter?)
  • Insert the tool in the collet of the machine (make sure the shank diameter is correct, insert the cutter up to the mark)
  • Set the speed matched to the workpiece / feed… on the machine (Important: Observe the information on the maximum speed on the milling cutter shank)
  • If necessary, mark the course of the groove
  • Secure / clamp the workpiece against slipping
  • If necessary, fix the guide stop
  • Use PPE / turn on suction
  • Milling (preferably counter-milling)
  • Check the groove by measuring, alternatively testing whether the component fits in the groove
  • If necessary, readjust and remill

Milling the groove instructions

The following steps explain briefly and concisely how a groove is milled with a RUWI milling table and a shank milling cutter with a milling diameter of 12mm.

Step 1: Choose the right cutter

The right milling cutter is crucial for creating the desired groove shape (e.g. V-groove, T-groove, rounded groove). It is imperative that the milling tool is the correct diameter and depth for the desired groove. It must also be considered whether the groove is to be milled in the face or in the edge. A disc grooving cutter is usually suitable for edges and a grooving cutter with a high shank for a groove in the surface. It is important that the tool selected is appropriate for the material being cut and is also compatible with the machine being used. The shank diameter, the speed range of the milling head and the machine should be coordinated.

Step 2: Set up the cutter on the machine

  1. Make sure that the router is switched off and not under voltage before you start changing the tool.
  2. Open the tool holder by holding the spindle with one open-end wrench while opening the collet nut with the other. Depending on the machine type, the spindle can also be locked with a button on the housing.
  3. Insert the cutter into the tool holder. It is important that the milling head is pushed into the collet up to the mark on the shank, and make sure that both the milling cutter and the tool holder are free of dirt and that it sits securely and without play.
  4. Tighten the clamping nut again to fix the cutter.
  5. You can now start editing. However, it is important to note that the router bit is properly assembled before turning on the router to avoid injury. It is recommended that you read and follow the manufacturer’s instructions to ensure the cutter is installed properly.

Step 3: Adjust stop jaws

The screws on the stop jaws on the stop ruler are loosened and these can then be pushed to the desired position and height. The stop jaws are then fixed again. It is important that the stop jaws have sufficient distance to the tool, but at the same time there should not be any large free spaces so that the workpiece cannot tilt or catch there. The entire stop ruler with the mounted stop jaws can then be pushed to the correct depth and fixed.

Adjusting the stop jaws on the RUWI milling table
Adjusting the stop jaws on the RUWI milling table

Step 4: Adjusting the cutter height

To set the correct cutter height, it is advisable to use a depth gauge. This is placed on the milling table so that the measuring tip hits the milling cutter. The milling cutter is then adjusted with the height adjustment until the desired milling cutter height is reached. Alternatively, you can mark the desired groove depth on the edge of the workpiece and turn the milling tool up until it matches the marking. However, it is always advisable to carry out a test cut before starting the final machining in order to check the dimensions again and adjust them if necessary.

Setting the milling height
Setting the milling height

Step 5: Mill a groove in the wood

Mount a tool cover and switch on the suction. Use your PPE (Personal Protective Equipment) such as safety goggles, hearing protection and a dust mask. Keep your fingers away from the danger area. Push the workpiece along the stop jaws and pay attention to the correct feed rate. If this is too low, this can lead to burns, while a feed rate that is too high often leads to inaccurate work results due to scores, planing marks and tears and puts a strain on the milling tool and the motor.

To ensure that the workpiece lies snugly on the router table, it can be helpful to use an additional hold-down device or a wooden strip clamped to the stop jaws.

Step 6: Result and conclusion

After the first pass of milling (preferably on a test piece) you should inspect the groove to ensure it has the desired dimensions and a clean finish. If the groove does not meet the requirements, you should correct the appropriate settings on the machine and carry out another milling pass.

With the right machine, the right tool and a little experience, you will quickly find that you can achieve perfect work results when milling a groove.

Tip: In general, you should mill in the opposite direction (the milling cutter turns against the feed direction) Downcut milling = increased risk of accidents!

What machines and tools are there for milling grooves?

machines :

  • (Hand) router
  • Milling table
  • CNC milling machine
  • Router table

Tools :

  • Disk grooving cutter, in different groove thicknesses, some with ball bearings in different diameters, each matched to the size of the flat dowel (Lamello)
  • Groove cutters with different shank diameters and shank lengths, different cutter diameters and cutter heights, fixed cutting edges and with indexable inserts, with two, three or more cutters, basic cutting cutters (the front side is ground and you can also plunge/drill into the wood) or only flank-cutting groove cutters
  • T-Nut milling cutter (as a screw guide for hexagon screws/nuts, sliding blocks, screw clamps, keyhole suspension)
  • V-groove cutter (for lettering, decorative grooves, emphasizing joints)
  • Groove with rounding on the front side / coving cutter (for decorative grooves, drain channel / juice groove on cutting boards, handle strips + stair handrails…)
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