The jackhammer, also called hammer-chisel, advantageously replaces the mass and avoids working as a convict during the demolition work. It can be pneumatic (connected to a compressor) or, as here, electric.
The apparatus used is of medium size with a weight of between 6 and 15 kg (here 11 kg). Handy, it is easily transportable and allows the vertical, horizontal and 45° demolition of slabs, walls, partitions and walls of any kind (concrete, stone, brick, blockwork). Conversely, large jackhammers, better known as "breakers", weigh more than 20 kg and are designed for the vertical demolition of concrete floors and foundations over large areas.
The type of jackhammer used here is equipped with an electric motor with a power generally between 1500 and 1600 W. Located at the rear of the machine and positioned vertically, it rotates a crankshaft. The latter actuates a piston that comes knocking at the end of stroke a chisel, or a detachable chisel mounted on a mandrel (or tool holder), located at the front of the device. The chuck works in translation (it does not turn): impossible to use to drill a hole, his only task is to chisel to break! But the engine power is not the only criterion of choice to buy or rent this type of tool. It must take into account its strike force, expressed in joules (J), depending on the work to be done (here 18 J at a rate of 2000 cps / min). As for boxers, the weight of the device also has an influence on its punching power: the heavier it is, the more it is effective. A hammer weighing 6 kg does not provide more than 12 J, but beyond 20 kg, it can reach up to 75 J / stroke, obviously to the detriment of its maneuverability.
On the price side, medium-sized electric hammers are expensive for occasional use: between 800 and more than € 1,500 (Dewalt, Hilti...). The rental remains the best solution: from 65 € per day and 98 € on weekends (for a 10 kg machine at Loxam for example) with a chipping tool included. Attention, the second tool is often extra.
2) Main handle
3) Auxiliary handle
4) Knob adjustment button
5) Cooling hearing
6) Clamping wheel
7) Mandrel orientation wheel
9) Flat chisel
10) Sharp chisel
A grip under pressure
The action of the jackhammer is simple. After quickly inserting the chipping tool corresponding to the task to be performed in the SDS Max chuck, the hammer plugs into a socket connected to a 10 A circuit breaker. If an extension cord is needed, you can use a cable to 3 x 1.5 mm2 up to 30 m, over a 3 x 2.5 mm cable2 does the trick. Before starting the tool, check that the wire is far enough away from the work area. Grasp the machine firmly with both handles and turn it on. Apply the jackhammer to the area to be broken and press the tool for percussion. Do a little touch, guiding it and moving it as the work progresses. Do not weigh all your weight on the device, you can quickly get tired and pinch the chisel. Manufacturers recommend a pressure of about 30 kg - obviously stronger but short-lived on a difficult area. Take regular breaks, about every hour, to avoid overheating and fatigue, because even with 11 kg the hammer becomes heavy to handle. Finally, check tool wear and chuck lubrication. If the tool is blunt, change it or sharpen it. The hirers propose packages for the sharpening of the pointerolles, spades and scissors: inquire about the conditions.
Check that the chuck is well greased and the chisel clean, before fitting the cutting tool. The renter normally offers you a tool already lubricated (or new).
The fitting of the chisel is fast. Simply slide it into the SDS Max toolholder until you reach the lock "click". To unlock, pull on the chuck collar and tool.
The start button is located under the main handle. With the device in the working position, operate the switch. Press the machine to get the percussion.
The adjustable handle is placed almost at the center of gravity of the jackhammer, ensuring a good balance for a comfortable grip and easy transport.
The typing rate is adjustable on this type of machine according to the work to be done. It varies from 1 to 7: low for chiselling and strong for routing.
Protect yourself The jackhammer transmits more or less contained vibrations, causes shrapnel, generates rubble and often has a high noise level (105 dB here). Even during short-term work, equip yourself with a helmet or ear plugs and safety glasses. Protect your hands with docker or anti-vibration gloves (see Instructions for use "Which gloves for which use", System D n° 805, February 2013), and put on some safety shoes.
Hold the camera firmly with both hands so as not to be unbalanced at the moment of percussion. Stay alert and always look at the area you are breaking to avoid scree.
Difficult to measure the pressure: too weak, the work does not advance; too powerful, the tool can heat up. If you are demolishing hard material, make as much of a body as possible.
Vertical chiselling is not a problem. To break a slab, start on the edge to weaken the concrete and back as you demolish.
The device is equipped with a ring that allows to turn the chuck in twelve positions and thus find the right orientation of stitching, especially when using a flat chisel, as here.
For the demolition of a stone, pebble or brick wall, chisel the joints to loosen the stones. Give angle to the jackhammer for better penetration.
This type of chipper is quite light (11 kg), but from 15 kg, the weight is quickly felt. By positioning the auxiliary handle on top, the work is more comfortable.
The machine is manageable enough to break the angle at the top of a wall. The wide rear handle allows a good guiding and the auxiliary handle an effective maintenance. Cement and concrete burst without problem with a sharp burin.
It may happen that the tool gets stuck in a loose part of an old wall. Make small circular movements to reach a rigid area to restart the strike and clear the tool.
Use your thigh as a support to guide the tool and gain stability. Especially if the chisel hangs badly on the surface during the attack.
For horizontal chipping, keep a reserve of 10 cm above the ground to avoid clogging the unit. To relieve your back, rest on your legs with your elbows.
Clean the jackhammer before storing it or returning it to the renter. Use a dry cloth or, better still, an air compressor to remove dust from the air vents.
The chisels adapted to the SDS Max system have a series of small grooves that can become dirty and interfere with the fitting. Clean and / or lubricate them.
The vertical breaker for which purpose?
The "concrete breaker" is a big hammer, quite heavy (20 to 30 kg). Highly used by building professionals, it is designed for the vertical demolition of concrete slabs, foundations of large areas. The chisels are hexagonal with a diameter of 30 mm. No need to exert strong pressure: the weight of the device and the blows are sufficient for a good performance. The striking force of the breaker used here is for example 50 joules for a rate of 1200 cps / min.
The main handle of the device has two springs that dampen vibrations. Very effective, they allow a prolonged use of the chisel without feeling tired.