common power tools

Sometimes hand tools are not practical for reasons of speed and accuracy. A variety of power tools are used during aircraft maintenance. Cutting tools used in an aircraft environment are generally pneumatically operated. Electrically driven cutting tools would be dangerous as they produce sparks which may ignite fuel vapours. The power for the pneumatic tools is supplied via a compressor that supplies air at around 80 p.s.i. The compressor normally incorporates a water trap so that the air is as dry as possible. The air supply is normally supplied via metal pipelines to a quick release coupling. The engineer will normally connect the power tools to the coupling via a plastic or rubber flexible hose. Many different types of pneumatic power tools are used, mainly by the airframe and engine engineers. The most common tools used are pneumatic (windy) drills, rivetting hammers for solid rivets, blind rivetting tools, pneumatic shears, pneumatic sanders, rivet croppers and millers.

3.2.1ELECTRIC HAND DRILLS

(See diagram below). These may be dangerous to use unless they are kept in good condition and handled carefully.

1. Always check the condition of the lead and plug. Do not use the drill if it is damaged in any way.

2. Make sure the job is firmly secured in a vice or on the drill platform.

3. Use a lubricant to keep the point of the drill cool; kerosene is suitable for most metals.

4. Do not force feed or the drill may break.

5. If swarf builds up at the drill point, stop the machine before attempting to clear it away.

6. Always wear goggles to protect your eyes.

Electric Drill Drill Stand

3.2.2PNEUMATIC TOOLS

These are used mainly in structural repair work.

Air Operated (Windy) Drills (see diagrams below). These are available in either straight or pistol grip form. They will, depending on size, accept drills up to 8mm diameter. Angled and off-set drills are provisioned for drilling holes in restricted positions. These drills require a separate collet for each size of drill.

Rotary Saw. Used primarily for cutting sheets of metal both on and off aircraft. It may also be used for cutting plywood and plastic. The tool illustrated can cut steel and alloy of thickness 0.8mm and 2mm respectively.

Pneumatic Shears This tool is designed to cut sheet material up to 14 SWG in mild steel or 12 SWG in light alloy. Cutting is achieved by the action of a

reciprocating shear blade against a stationary anvil blade. Stellite tipped blades are available for cutting stainless steel or titanium alloy.

Pneumatic Riveting Hammers. Many types are available to suit a variety of solid rivet sizes. They all operate on a similar principle as shown in the diagram below. The air pressure supply controlled by the throttle button or lever, causes the piston to oscillate rapidly backwards and forwards in the barrel. The piston delivers blows to the rivet via the interchangeable snap. An adjustable air

regulating screw varies the maximum rate and power of the gun. A typical rate is 1,500 blows per minute.

Pneumatic Blind Riveters. These are designed for easy forming of various types of blind rivets. There is usually a special riveter for each type of rivet. Sometimes the riveter is air operated, but many incorporate a hydraulic intensifier. Many types exist, so only a selection is shown below.

Mandrel Cropping Tool. The air operated cropping tool is used to cut off the protruding mandrel stems of Avdel rivets after they have been set. The tool incorporates two cutting jaws which sever the rivet mandrel when the control button is pressed. The cut mandrel will still need to be milled down with the milling tool, to give a clean finish.

Rivet Miller. This air operated tool is used mainly for milling down protruding Avdel rivet mandrels. It usually has telescopic legs and a micrometer adjustment to that the depth of cut can be accurately set.

3.2.3CARE OF AIR OPERATED TOOLS & SAFETY PRECAUTIONS

When used, maintained and stored correctly, air operated tools have a long and trouble free life. Their great enemies are lack of lubrication and the entry of moisture and foreign particles introduced via the air supply. These effects can be reduced as follows:

1. Drain the compressor oil and water traps at least daily and more often if the tools are in prolonged use.

2. Ensure that both male and female parts of the air supply couplings are clean before connections are made.

3. Before using a tool, introduce about six drops of the specified lubricant into the air supply opening.

4. Before storage, carry out the oiling procedure again, operating the tool slowly to distribute the oil.

The broaching action of most expansion riveting tools is dependent of the grip of their serrated jaws. If the jaws start to slip, stop riveting and clean out the jaw assembly.

Safety. These tools should be perfectly safe during normal use but they all can be dangerous if handled incorrectly or carelessly. Before connecting a power tool to it's supply, you should be aware of it's potential dangers and plan how to avoid them. Warning notices often give some indication of potential dangers and they should be obeyed. Other precautions include:

• Keep your hands, hair and clothing clear of the moving parts of tools.

• Wear goggles, ear defenders and protective clothing as the circumstances demand.

• Do not leave an unused tool connected to the power supply.

• Always operate riveting hammers against a resistance, especially when testing it's action.

Note. Most accidents occur due to inexperienced operators fooling around with power tools.