- Different types of grooving machines
- A double diamond disc
- Set grooving width
- Bleeding: rules to follow
To perform constant width and depth grooves in walls and partitions, this tool, equipped with two diamond discs, cuts all types of materials.
To hide a sheath or pipe, simply bleed into the wall. The operation requires adapted tools, especially if the installation of the electrical network or plumbing requires many cuts. With a hammer and chisel, or an angle grinder, the intervention is possible, but it must be done in several times and the task quickly becomes painful. Without guidance, the straight line of constant width and depth is difficult to obtain.
Different types of grooving machines
Unlike an angle grinder, the groover has two parallel cutting discs, adjustable in width using spacers and deep thanks to a lockable dipstick.
The most common power-operated cordless routers (when purchased or rented) are equipped with a motor whose power varies from 1,400 to 1,800 W. The diameter of the discs ranges from 125 to 180 mm, and the depth of cut can reach 60 mm. Depending on the model, the cutting width varies between 6 and 47 mm.
A double diamond disc
All machines must be used with segment-rim diamond discs. They allow cutting most materials (concrete, breeze block, brick, etc.).
Abrasive discs are to be excluded: while wearing in contact with the support, their diameter decreases - unlike diamond discs -, making the adjustment of the depth of cut inefficient. The size of the grooves for the passage of a sheath (or tubes PER) not exceeding 40 mm wide, it is useless to choose a too big machine.
Depending on the work to be done and the number of days of use, the question of buying or renting equipment may arise. Prices range from € 150 for entry-level models to over € 1,000 for pros.
A good quality machine costs around 400 €. At this price, we must add the purchase of a vacuum cleaner (if you do not want to sacrifice that of the house!): Essential because of the amount of dust released. For rent, it takes about 100 € on weekends and 50 € on average for the vacuum cleaner. This is the ideal solution for occasional use, as rental companies often offer professional equipment.
Set grooving width
The disassembly and disassembly of the disks is carried out as on a grinder. Both discs must be changed at the same time, respecting the direction of rotation. Spacers are used to adjust the cutting width, from 6 to 30 mm, with intermediates of 9, 12, 15, 18, 21, 24 and 27 mm. Width and depth are determined by the size of the element to be embedded (a too wide kerf implies a longer filler time). Grooving is done by pushing or pulling the device, without forcing the movement.
The attack starts with the motor running, first putting the back of the machine on the support and then tilting it forward so that the discs come into contact with the wall. The bleeding is then hollowed out with a hammer and chisel or with the aid of a perforator equipped with a chisel (flat or pointed). Despite easy handling, safety must not be neglected: protective goggles, gloves, helmet or earplugs are essential.
The protection of the user is provided by two casings: one has a handle, the other acts as a pad. Assembly and disassembly is carried out with an Allen key.
Separated from the engine block, the two casings open almost 180°, thus clearing the cutting discs. Rotation is possible thanks to an axis located at the back.
Using the lug wrench supplied with the machine, unlock the disk lock nut.
To unlock the disk tightening nut, it is necessary to immobilize the shaft with a button provided for this purpose.
The nut has only one direction of assembly, the shoulder must press, either on the disk, or on the spacer according to the desired width of cut. Otherwise the tightening is inefficient.
The mounting direction of the cutting discs is represented by an arrow, which corresponds to the direction of rotation of the shaft. The discs are necessarily mounted in the same direction.
Segmented rim diamond discs cut most construction materials: concrete, plaster, brick, aerated concrete...
The first cutting disc is mounted directly at the end of the shaft. It serves as a reference for the cut and, whatever the setting, it always remains in the same location. Only the second disc moves according to the width of the desired groove.
The cutting width is obtained by means of spacers (four rings of 6 mm and one of 3 mm). The last ring compensates the thickness of the discs (1.5 mm each).
All rings must be installed, even if the cutting width varies (minimum 6 mm, maximum 30 mm), otherwise the tightening of the discs is impossible.
The depth of the groove can be easily adjusted using a knurled screw and a nut. The latter also serves as a stop on the lower cover.
Once the discs have been adjusted to the correct width, the upper guard must be folded down. Be careful to insert the stop pin of the sump into the guide groove.
The auxiliary handle is adjusted for a better comfort of use. Two screws and notches facilitate its positioning. The key is stored in a housing provided for this purpose.
At the front and rear of the sump, a notch allows you to follow the cutting mark, regardless of the position of the machine.
A stabilizer wheel, located on one side of the unit, prevents any lateral "skidding". It comes in reinforcement of the lower case, which acts as a skate.
With the grooving machine generating a lot of dust, connect it (crankcase tip) to a slave vacuum, if possible, so that both devices start at the same time.
The slide on / off button must be "pulled" hard enough to shut off the engine. The discs continue to run a few seconds after stopping.
To groove, firmly hold the machine by both handles to prevent backlash. The discs must rotate at full speed before contact with the wall. Wear goggles, gloves and earmuffs.
The cut can be from bottom to top or from top to bottom. This second solution is slightly more comfortable: it is indeed easier to pull the device down.
Once the cut is complete, remove the bleeding, either with a hammer and chisel, or with a perforator equipped with a flat chisel. It will only remain to slip the sheath and close the bleeding.
Bleeding: rules to follow
• The slits must be executed according to strict professional rules set by the DTU (unified technical document), especially if your electrical installation must be attested by the Consuel.
• In horizontal alignment, the kerf can not exceed a maximum length of 50 cm from the angle of the wall, and a maximum of 1 m from either side of a vertical kerf.
• In vertical route, it can not exceed 1.30 m above the finished ground. Starting from the ceiling, it must be executed over a maximum length of 80 cm, more than 20 cm from the corners or edges of the partitions. In the same partition, the distance between two vertical grooves is at least 1.60 m.
• It is forbidden to slant at an angle, all the way up a partition, along its length and above a door.
• The electric wires must be inserted in a sheath before being hidden in the kerf.