JACK HAMMER

INTRODUCTION

Also called as pneumatic drill or demolition hammer 

It is a pneumatic or electro-mechanical tool that combines a hammer directly with a chisel. It was invented by Charles Brady King.

Hand-held jackhammers are typically powered by compressed air, but some use electric motors.

Larger jackhammers, such as rig mounted hammers used on construction machinery, are usually hydraulically powered. They are usually used to break up rock, pavement, and concrete.

A jackhammer operates by driving an internal hammer up and down. The hammer is first driven down to strike the back of the bit and then back up to return the hammer to the original position to repeat the cycle. The bit usually recovers from the stroke by means of a spring. The effectiveness of the jackhammer is dependent on how much force is applied to the tool.

TYPESPneumaticElectromechanical or electropneumatic

Hydraulic

PNEUMATIC –

Also known as a pneumatic drill or pneumatic hammer It is jackhammer that uses compressed air as the power source. Air supply usually comes from a portable air compressor driven by a 

diesel engine. Reciprocating compressors were formerly used.  The unit comprised a reciprocating compressor driven, through a 

centrifugal clutch, by a diesel engine. The engine'sgovernor provided only two speeds:1. idling, when the clutch was disengaged2. maximum, when the clutch was engaged and the compressor was

running Modern versions use rotary compressors and have more sophisticated

variable governors. The unit is usually mounted on a trailer and sometimes includes an electrical generator to supply lights or electric power tools.

Additionally, some users of pneumatic jackhammers may use a pneumatic lubricator which is placed in series with the air hose powering the air hammer. This increases the life and performance of the jackhammer. Specific lubricant is filled in the pneumatic lubricator. Furthermore, air compressors typically incorporate moisture into the compressed air leading to freeze-ups of the jackhammer or air hammer in cold weather.

ELECTROMECHANICAL OR ELECTROPNEUMATIC

Variety of sizes from about 12 lbs - 65 lbs. Require an external power source, but do not require a

compressor. Although in the past these tools did not have the power of an air or pneumatic hammer, this is changing with newer brushless-motor tools coming close to the power of a pneumatic tool and in some cases even matching it. Electric powered tools are useful for locations where access to a compressor is limited or impractical, such as inside a building, in a crowded construction site, or in a remote location.

Electropneumatic tools use a variety of chucks for attaching chisels, but the most common are SDS-max, 7/8" Hex, TE-S, and 1-1/8" Hex.

The connection end size is also related to the breaking energy of the tool.

HYDRAULIC

A hydraulic jackhammer, typically much larger than portable ones, may be fitted to mechanical excavators or backhoes and is widely used for roadwork, quarrying and general demolition or construction groundwork.

These larger machine mounted breakers are known as Rig Mounted, or Machine Mounted Breakers. Such tools can also be used against vertical walls (or ceilings for that matter), since the vehicles involved are massive enough and powerful enough to exert the forces involved without needing the help of gravity in operating the tool.

Pneumatic or hydraulic tools are particularly likely to be used in mines where there is an explosion risk (such as underground coal mines), since they lack any high-power electrical circuitry that might cause a triggering spark.

Hydraulic breakers usually use a hydraulic motor driving a sealed pneumatic hammer system, as a hydraulic hammer would develop a low strike speed and transfer unacceptable shock loads to the pump system.

Advances in technology have allowed for portable hydraulic breakers. The jackhammer is connected with hydraulic hoses to a portable hydraulic powerpack: either a petrol or diesel engine driving a hydraulic pump; or a mini-excavator or skid-steer via a power take-off driveshaft to the machine's hydraulic system.

Hydraulic power sources are more efficient than air compressors, making the kit smaller, cheaper or more powerful than a comparable pneumatic version.

GLOSSARY OF TERMS Bit – This is a portion of drill which contact with

rocks and disintegrates it. Burden – Horizontal distance from a rock face to

the first row of drill holes or the distance between rows of drill holes

Coupling – a short, hollow steel pipe having interior threads. Coupling is used to hold the pieces of drill steel together or to the shank. Percussion energy is transferred through the steel; not the coupling. Therefore coupling must allow the drill steel to butt together.

Cuttings – The disintegrated rock particles that are removed from a hole.

Drifter – It is an air operated percussion type drill similar to jackhammer; that is required mechanical mounting.

BITS (CHISELS)

Bit types include: Spade - provides flat finish for concrete or edging in

asphalt or dirt Flat tip - allows direction control or finer edge finish Point - general breaking Stake driver - drives concrete form stakes Scabbler - finishes surface smooth or for cleaning

prior to bonding Flex chisel - flexible metal blade (attached to shank

with bolts) for tile removal and scraping Bushing tool - multiple carbide points for cleaning up

seams and knocking down rough spots in concrete

CHISEL SHARPENINGChisels may be sharpened in a shop or

with an angle grinder with grinding disc. After sharpening, they must then be heat

treated to restore the integrity of the steel before use. 

SKETCH OF JACKHAMMER

WORKING OF JACKHAMMER

When the valve is in the position shown here, air enters through the thick yellow hose at the top and follows the thinner paths shown in yellow, pushing the piston (red) downward and smashing the hammer (green and gray) into the ground.

As the piston moves down, air flows back up through one of the pipes and pushes the blue valve over to the right, so the air now follows the brown paths and exits.

WORKING OF JACKHAMMER – CONT…. Drilling unit consists – Hammer, drill steel and bit

Compressed air flows through a hammer, it causes a piston to reciprocate at a speed up to 2200 blows/minute.

Energy of piston is transmitted to a bit through a drill steel

Air flows through a hole in the drill steel and the bit to remove the cuttings from the hole and to cool the bit.

Drill steel is rotated slightly following each blow so that the cutting edge of the bit will not strike at the same place each time.

SUITABILITY OF JACKHAMMER With or without pusher leg (Pneumatic powered)

for hole length upto 3.5m and dia. 32-38mm – Medium hard rock to hard rocks, small output, small size horizontal mine openings and pin holes for services.

Hand held – Funnel chamber excavation, shaft sinking, winzing in all and types of rocks

Electric breakers from Kennards come in 10kg, 15kg and 33kg models. - They can be used for small to medium demolition projects like tile lifting, bitumen cutting and digging clay.

The 10kg option is light enough to work horizontally but still break up concrete with a thickness of 50mm.

The largest model will break concrete of up to 100mm in thickness, and has the equivalent impact of a 28kg pneumatic hammer.

SUITABILITY OF JACKHAMMER – CONT….. A jack hammer trolley is ideal for easy removal of lino and floor tiles, and has built-in shock absorption and an anti-vibration device to ensure the job isn't harder than it needs to be.

Pneumatic jack hammers are suitable for all drilling purposes in underground and open-pit mining due to their low weight and high stability, however, they need expensive power supply. (Small Scale Mining)

The electric hammer should be considered as an alternative to pneumatic systems in small mines with only few working places. Its low Input of primary energy needed and environmental soundness are marks of the electric hammer, however, high cost of installation of electric power supply should be considered in the case that it is not available.

SAFETY TIPS FOR USING JACK HAMMER DRILLSJack hammer drills, if used incorrectly, can be very dangerous

tools – Wear necessary protective clothing, including steel toe boots, 

eye protection, andsafety gloves and hearing/ear protection. Do not use a jack hammer drill for a long period of time: rest or alternate

where necessary. Place the jack hammer drill and compressors in correct and safe places. Inspect a jack hammer drill before each use, including checking for

breaks or cracks in hoses and fraying or breakages in electrical wires. Use a jack hammer drill of appropriate weight, the lighter the better. Use the correct point for the correct job. Lift a jack hammer drill according to the correct moving and handling

instructions. Check for dust and use water compression where necessary. Don’t use a jack hammer drill beyond a cutting bit. Shut off a jack hammer drill and all related equipment correctly after

use. Barricade work area as much as possible when using jack hammer drills. Release air trigger when lifting the relevant jack hammer drill. Sling electrical cord over shoulder to avoid swerving and potential

electrocution.

METHODS Full-sized portable jackhammer is impractical for use

against walls and steep slopes, except by a very strong person, as the user would have to both support the weight of the tool, and push the tool back against the work after each blow.

A technique developed by experienced workers is a two-person team to overcome this obstacle of gravity: one person operates the hammer and the second assists by holding the hammer either on their shoulders or cradled in their arms. Both use their combined weight to push the bit into the workface. This method is commonly referred to as horizontal jackhammering.

Another method is overhead jackhammering, requiring strength conditioning and endurance to hold a smaller jackhammer, called a rivet buster, over one's head. To make overhead work safer a platform can be used. One such platform is a P.A.M. (Positioner Actuator Manipulator). This unit takes all the weight and vibration from the user.

HEALTH EFFECTS The sound of the hammer blows, combined with the explosive

air exhaust, makes pneumatic jackhammers dangerously loud, emitting 100decibels at two meters. Sound-blocking earmuffs must be worn by the operator to prevent a form of hearing damage of which tinnitus is the main symptom.

Use has been linked to Raynaud's Disease (excessively reduced blood flow in response to cold or emotional stress, causing discoloration of the fingers, toes, and

occasionally other areas). Prolonged exposure to the pronounced vibration set up by the

tool can lead to blood-circulation failures in the fingers, a condition known as white finger. Applying athletic tape is not effective in preventing white finger but seems to help alleviate some of its discomfort. Pneumatic drill usage can also lead to a predisposition for development of carpal tunnel syndrome.(It

is a median entrapment neuropathy that causes paresthesia, pain, numbness, and other symptomsin the distribution of the median nerve due to its compression at the wrist in the carpal tunnel.)

Using a jackhammer to break up concrete pavement may expose the operator to hazardous dust containing respirable crystalline silica (RCS)