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When it comes to installing electrical conduits or pipes, the grooving machine is the necessary tool! Equipped with two diamond discs, it digs vertical or horizontal grooves of constant depth and width in most walls and partitions, whether brick, block, cellular concrete or plaster.

Wall groover

detail of a grooving machine

1 Blocking the tree
2 Stabilizing Roller
3 switch
4 main handle
5 Auxiliary handle
6 Vacuum connection
7 Depth adjustment

details of a grooving machine

9 Diamond disc
10 intersecting
11 Nut

Handling the grooving machine

Several discs for the grooving machine

  • Multidisk machine
The most commonly used grooving patterns have two cutting discs (three or four for professional tools). The power of electric motors ranges from 1,200 to 2,000 W, with disc diameters of 125, 150 and 180 mm for grooves ranging from 6 to 50 mm wide and 6 to 60 mm deep.

Cutting width with a grooving machine

  • Variable cutting width
The width of the bleeding varies here from 6 to 28 mm approximately: it depends on the thickness of the discs and the number of spacers placed between them. Whatever the width of the groove, the six washers (4 mm thick each) must be installed on the motor shaft.

Make grooves

  • Adjustable depth
The depth of the groove is adjusted using a knurled screw. The discs remain in position, it is the lower guard that moves: with the model tested (Einhell), one can achieve grooves 8 to 30 mm deep. This housing also serves as a window for passing the disks and pad in contact with the wall to be machined.

Remove the discs from the grooving machine

  • Protected disks
The grooving machine is configured much like an angle grinder with a gearbox motor. To access the discs, you have to remove the auxiliary handle, remove the cast aluminum upper housing and the metal mobile housing. Make sure to unplug the unit before.

Disassemble the disc from a grooving machine

  • Disassembly of disks
Once the screws are removed, the housings are disconnected from the engine block. They open about 180° thanks to a pivot axis, to release the cutting discs and make them accessible. The tightening nut is unlocked by means of a generally provided spigot. To loosen the nut, the tool shaft must be locked with the knob on the other side of the grooving head.

Two diamond discs

Diamond disc for grooving machine

The grooving machine should be used with segment rim or full rim diamond discs. The first cut most building materials (concrete, cinder block, brick, cellular concrete...). Solid discs are for use in tiles or plasterboard for more delicate cuts. Never use abrasive discs. Used, both discs must be changed at the same time to ensure maximum efficiency.

Installation and settings of the wall chaser

Mount the discs on the grooving machine

  • Mounting
The first disc is mounted at the base of the shaft directly on the drive flange. It serves as a reference for the cut and, regardless of the setting, always remains in the same location. This is the second disc that moves according to the desired width of the groove.

Mount the disc of the grooving machine

  • Centering
Centered, the spacers are stacked on top of each other on the motor shaft. To achieve perfect centering, a shoulder corresponding to the diameter of the bore of the discs is machined on the drive flange and on one of the spacers. If the first disc is still mounted on the drive flange, the second, it is installed on the spacer equipped with the shoulder.

Direction of rotation of the discs

  • The direction of rotation
The discs are positioned so that the printed side is visible. An arrow indicates the direction of rotation. Both disks must be mounted in the same direction to avoid any problem. On this machine, the nut is reversible and is mounted on the M14 thread of the shaft in both directions.

Connect a vacuum cleaner to the grooving machine

  • Dust extraction
A grooving machine generates a lot of fine dust, which is harmful for the respiratory tract. It must be connected to a construction vacuum cleaner. Located at the back of the guard, the fitting is equipped with two sealed rubber gaskets (one at the inlet and one at the outlet) to prevent dust from escaping.

Starting the grooving machine

  • Secure startup
The machine is started by means of a so-called "dead man" switch. Simply push the small tab at the front to unlock the switch before pressing it. As soon as the pressure relaxes, the engine is shut down.
Be careful, the discs are still running for a few seconds.

Machines at all prices


On average, the size of a kerf does not exceed 40 mm wide and 25 mm deep.

  • If the grooves are to be made in plasterboard partitions or plasterboard, a power of 1200 to 1400 W is enough with discs Ø 125 mm.
  • For load-bearing walls made of bricks or blocks, engines from 1500 to 2000 W are more enduring. They are often accompanied by Ø 150 or 180 mm discs.
The price of a grooving machine ranges from € 100 for an entry-level model to € 1,000 for a professional machine. If the work is casual, the renting can be a solution. A 1,500 W reamer with Ø 180 mm discs costs around € 60 per day or € 100 for a weekend.

Grooving with two hands

Handling the grooving machine with both hands

  • A grooving machine handles with both hands.
  • With the discs running at full speed, press the back of the machine onto the path and gently tip it toward the support.

The groover moves backwards

  • The machine moves backwards.
  • She works in the opposite direction of the rotation of the discs that turn forward.
Do not forget to wear gloves, goggles and earplugs or earmuffs for your safety.

Tips for using a grooving machine

  • To obtain a regular bleed, it must be done at once and without stopping.
  • To facilitate the maneuver, a stabilizer wheel located on one side of the grooving machine, prevents the machine to skid and deviate from its path.

Make bleeds

  • According to the standards in force, the slits must never be practiced at an angle.
  • They must cross perpendicularly.
  • At the intersection, a slight cut can be made at an angle so that the sheath can pass without making a right angle.

Evince bleeding

  • The cut is complete, it remains to hollow out bleeding.
  • The best technique is to use a hammer and a flat chisel.
  • Position the chisel on the edge of the part to be removed and then tap with the hammer.
  • Then slide the sheath and fill in the bleeding.

Tips from handymen

Detect materials in the wall

For any installation, the Electric wires must be inserted in ducts before being concealed in the bleeding.
To save time, slip the future sheath or pipe between the groove discs and adjust the cutting width as closely as possible.
Finally, before starting a bleeding in a wall or a partition, make sure that there is no obstacle, such as a metal wall jamb, an electrical sheath... The use of a material detector can then be very useful to avoid unpleasant surprises.

Video Instruction: How to chase a wall and fit a metal back box - Chasing a Concrete Wall