REDISCOVERING THE AIR CHISEL
APPARATUS & EQUIPMENT
“A piece of cake,” Lieutenant McNally said to himself as he continued his size-up of the accident scene. McNally and his engine crew had responded to a report of a single vehicle collision with possible injuries and entrapment. The original dispatch information had been accurate; apparently, the driver struck a tree with a glancing blow to the left front corner of her midsized car. One car, one victim, one jammed door—no sweat, he thought. This would be a good time for Williams, the rookie, to try his hand at operating the hydraulic spreaders to pop the door open.
“Lieutenant!” It was the firefighter/ paramedic calling from inside the car. “She says her foot is caught in some of the bent floorboard. I’m immobilizing her head and neck—can’t check it out. Can you handle it?” “We have it,” McNally replied, “soon as we pop the door open.”
Williams and Clancy, the senior firefighter on the crew, connected both the hydraulic spreaders and the cutters to the generator using a dual hose setup and were ready for the door-opening procedure. Clancy created a purchase point above the door safety bolt with a halligan, and Williams inserted the spreader tips and started spreading the door open. The door didn’t pop open cleanly. Instead, the metal tore as the spreader tips widened. Then suddenly the gas-driven hydraulic generator stalled.
Clancy checked the fuel level in the tank even though he knew it was full. He replaced the gas cap and pulled on the starter cord five times without a sputter. “My guess is a fouled plug,” he called over to the lieutenant. “All right, Clancy, get the air chisel and get that door open. Williams, go hack to the engine and get a fresh spark for the generator.” So much for an easy job, sighed the lieutenant to himself.
Clancy, air chisel in hand, sized up the jagged metal and decided to cut directly through the safety bolt. Within 60 seconds the door was free and swung wide open. Williams still was working on the generator. Clancy examined the victim’s foot by the light of his hand lantern. Sure enough, the floorboard had entangled the victim’s foot and ankle, but it appeared uninjured.
Photos courtesy of author.
Clancy turned to the officer. “Lieutenant, I should be able to cut this metal away without any problem or injury to the victim.” The lieutenant walked over and squatted down to take a look. Then he called over his shoulder to Williams, who was yanking the generator’s power cord. “Williams, what’s the story with that plug?” “Spark plug’s not the problem, lieutenant,” replied the rookie. “I can’t find out what’s wrong with this thing.” McNally frowned and pulled Clancy toward him. “Okay, but be careful with that air chisel,” he whispered. “We don’t need anybody saying that the fire department tried to cut off her foot.” Within a minute the twisted metal was cut away and the victim’s foot was disentangled.
After the victim was packaged and sent to the hospital the engine crew members discussed their actions, looking for ways to improve. “You know,” Williams started, “I asked some of the guys and they said we don’t use the air chisels any more because we have the hydraulic rescue tools. Obviously that’s not the case, so I’d like to do some training with them, lieutenant.” “No problem,” the officer replied. “I’ll call training division in the morning.” It’s funny, he thought as he climbed into the engine, tonight we rediscovered a great piece of equipment.
The air chisel is one of the most frequently underrated and underutilized pieces of equipment carried on a fire apparatus. In fact, many departments don’t carry one at all. Since the development of power hydraulic rescue tools, it has become almost forgotten; comprehensive training information on its use is virtually nonexistent. In spite of this neglect, the air chisel should have a place in the repertoire of every rescue company.
The air chisel is effective not only in vehicle rescues but in other settings encountered by firefighters. It can be used to open up metal duct work in structures quickly, car hoods with melted hood releases, metal garage doors, and galvanized pipe as well as in many other applications. Often, using an air chisel can complete the job more efficiently and with less damage than other tools.
SELECTING THE PROPER AIR CHISEL
No doubt some companies have tried to use light-duty air chisels for heavy-duty cutting jobs, without success. These chisels, frequently referred to as “muffler guns,” are designed for cutting through vehicle exhaust pipes and sheet-metal body parts, not door safety bolts or hinges. Typically the regulator, hose, couplings, and gun of the light-duty air chisel are designed to operate in the 95 psi range.
More suitable for the majority of rescue incidents are the air chisels that come with adjustable regulators designed for operation between 95 and 250 psi; preset, nonadjustable, 300-psi units are better still. These have the power to cut through heavy metal objects with little difficulty. However, it is important to remember not to mix tool components of different power ratings, even if the couplings fit.
There are several considerations when selecting a system for purchase:
- The regulator inlet pressure required should be compatible with the proposed air supply, whether it be a 2216or 4500-psi SCBA cylinder, scuba cylinder, or compressor/cascade system.
- Oxygen should never be used as an air supply.
- The hose should be appropriate for the pressures that will be deliv-
- ered from the low-pressure, discharge side of the regulator. Very often the rating will be marked on the hose cover itself. Ten to 15 feet of hose is typical and adequate, but 30 feet provides a lot more freedom of movement.
- Selection of the gun is a matter of individual preference after considering anticipated needs. Points to consider include air consumption (which can range from 0.9 to 7.0 cu. ft./min.), overall size of the gun (with thought given to the possibility of working in tight spaces), and method of attaching the cutting chisels.
- To attach the chisels, some guns have retainers that are pulled back in a quick-connect manner; in others the retainer is attached to the chisel itself, with the chisel/retainer assembly then attached to the gun. Both attachment methods have minor drawbacks. Chisels in the quick-connect gun have
- fallen out when the retainer contacted the working surface. The screw-on retainer/chisel arrangement has a tendency to vibrate loose, resulting in a loss of cutting power that may go unnoticed by the inexperienced user. Another factor to consider is whether or not the chisel swivels when attached to the gun: The nonswivel type will be easier for the inexperienced user to operate, but the swivel type will provide greater flexibility in awkward or tight areas.
- There are several types of chisels
- available. Those most commonly used are the short and long curved cutters, the dual cutter, and the “T” cutter. The operator should be able to handle most situations with these four chisels. There are a variety of other chisels available to fulfill specific needs.
The dual cutter and the “T” cutter are designed for quick cutting on smooth sheet-metal surfaces. They both have a built-in guide that assists in positioning the gun at the most effective cutting angle. An experienced operator can easily cut through standard automobile sheet metal at the rate of one foot per second.
The curved cutter blade has a larger cutting edge than the dual or “T” cutter, making it ideal for cutting crumpled sheet metal. It’s also very useful in cutting solid metal objects such as door safety bolts, brake pedal assemblies, and automobile roof posts.
GETTING THE JOB DONE
Before starting any air chisel operation, the operator must study the manufacturer’s instructions and must wear appropriate eye protection, gloves, and protection for body parts exposed to jagged metal. In addition, the operator must consider the following:
- Keep couplings clean—do not drop them in the sand or dirt. Pneumatic couplings, like hydraulic couplings, operate very poorly if at all when gritty.
- Once all the components are connected, turn on the air supply completely and set the regulator to the
- appropriate operating pressure. The required pressure depends on the material to be cut. Generally, if the object is a safety bolt or other strong material, the maximum available pressure will be required. Lighter materials such as the sheet metal of a vehicle roof will require much less.
- A starter hole is required before the actual cutting. That can be created quickly by holding the gun at a 45degree angle at the surface and cutting into the metal with one corner of the chisel.
- Once the hole is created, the gun should be moved closer to the cutting surface. With the “T” or dual cutter, the built-in guide should run smoothly along the surface. If the long curved cutter is used, the operator can control the gun by grasping the shaft of the chisel with his free hand, well away from the cutting edge. While this may sound dangerous, there is actually little chance of injury. Certainly, an out-of-control gun is extremely dangerous to both rescuer and victim alike, but keeping firm, forward pressure on the gun while depressing the trigger fully will almost eliminate that possibility.
MAINTENANCE
Proper maintenance is vital to keeping an air chisel in peak operating condition. Air chisels require religious lubrication with pneumatic oil to perform properly. If not equipped with a built-in oiler, the operator must oil the gun between uses. Most often this is done by placing a few drops of oil down the barrel with the chisel removed and a few drops in the gun intake. This should be done before and after every training session and after every emergency use.
Just as important as cleanliness and proper lubrication are sharp chisels. There’s a great difference in cutting speed between a sharp chisel and a dulled chisel. While the “T” and dual cutters seldom need maintenance, the curved cutter tips can be sharpened very quickly with a 5-inch grinding wheel. The tip should not be allowed to overheat during the sharpening or it will lose its hardness. Prevent this problem by frequent cooling in water. Once tool operators see the difference in using sharp chisels, they will understand the importance of sharpening them after every use.
As with all rescue equipment, to get the maximum use out of the air chisel the firefighter must be given the opportunity to train and experiment with it and then to use it in an actual emergency setting. Only then will the firefighter be armed with the confidence and skill to get the job done the right way.
Rediscover the air chisel. Although it’s not the answer to all your cutting needs, one day you may be very glad you have it.