Aircraft Tools, Materials, and Processes

Learning Objectives

• Become familiar with tools and materials used for laboratory activities
• Identify sheet metal structures and differentiate between types of aircraft structure stress
• Explain and identify the difference between heat and non-heat treatment processes
• Identify solid shank rivets and special blind rivets, including their head markings
• Understand the correct procedure for installing rivets properly

Familiarization of Tools and Materials

• Aviation Maintenance Technicians use a wide variety of hand tools daily
• This section provides an overview of hand tools expected to be used by an AMT

Measuring Tools/Layout: Dimensions, Allowances, & Tolerances

• Familiarity with accepted measuring methods and units is necessary to determine distance, weight, speed, volume, temperature, and pressure
• Humans have devised many measuring methods over the ages
• Measurements in aviation uses the English (Imperial) and SI (metric) systems
• SI is short for Système International d'Unités
• SI is the modern version of the metric system, agreed upon by the USA and other nations

Measurement Unit Systems

• The International System of Units (SI) originates from selecting the meter for length and the kilogram for mass
• Metric units were created by the National Academy of Science and adopted by France in 1795
• The United States Congress legalized metric system use on July 28, 1866
• The metric Bill, signed into law on December 23, 1975, aimed to convert all U.S. measurements to metric
• The metric system is built on decimal units, and each basic unit can be multiplied or divided by ten
• The English unit system is familiar in English-speaking countries, using inch, second, and pound for length/time/weight
• Boeing aircraft documentation uses the English unit system
• Airbus documentation uses both Imperial and metric units

Rules and Scales

• Steel scales or rules are common in toolkits, in both 6- and 12-inch lengths
• They are for sheet metal layout and measurements when vernier/micrometer accuracy isn't needed
• Steel scales are made of tempered carbon steel or satin-finished stainless steel
• Scales can be graduated in fractions or decimals, in English or metric, and some have both

Sawing

• Sawing separates material and produces grooves and notches
• Saw blades include many teeth with cutting edges like chisels
• More than one tooth must contact the workpiece during sawing
• Teeth must point in the cutting direction

Saw Blade

• Pitch is the space from one tooth to the next
• Saw blades are rated by teeth number per inch of blade length
• Coarse blades are for soft materials
• Medium blades are for normal materials
• Fine blades are for hard materials

Filing

• Filing removes material from metal or wood
• Filing alters a part's size/shape by removing material
• Filing smoothes a surface without removing much material

File shapes

• The selection of a file shape depends on the size and shape of the surface to be worked
• Flat files work on flat or convex surfaces
• Triangular files have an equilateral triangle cross-section and are limited to angles greater than 60°
• Square files file keyways and enlarge square/rectangular holes
• Round files file small radii
• Half-round files file medium/large radii

Proper Working Position

• Bench vice adjustment is important for proper working position, at 2-3 inches below the elbow
• Hold the file handle with the right hand, pressing against the palm
• Press down on the file tip with the left hand palm or fingertips
• Left-handed individuals should hold the handle in their left hand and press on the file blade with their right hand
• Always ensure a file in use has a handle fitted, or else the tang can puncture the hand

Cleaning Dirty Files

• Files need cleaning often, as dirty files produce poor finish
• A file is brushed across with a file brush in a direction parallel to the teeth, in order to clean it

Hand-Held Drill Motors

• Pneumatic or air drills are most common for drilling aircraft sheet metal
• Air drills offer safety advantages over electric drills
• Electric drill sparking can ignite fuel or oil vapor
• Air hoses are less hazardous than electrical cables in confined spaces
• Air drills allow control by varying trigger pressure to adjust speed & torque, and have quick-change chucks or keyed chucks

Common Drill and Angle Motors

• Pistol-grip drills and straight drills are most frequently utilized
• Angle drill motors or power vanes are designed to be operated in tight or under-limited access places
• 30°, 45°, and 90° head angles are available for angle drill motors

The Chuck of a Drill Machine

• The chuck of a drill machine is a tool to tighten the drill, countersinking bit, reamer, etc
• When using the keyed chuck, use the correct-size chuck key which should mesh easily but firmly
• Turn the key counter-clockwise to insert the tool into the chuck jaws, holding the key securely to prevent slipping
• Turn the key clockwise, tightening the tool securely in the jaws. Use at least two different keyholes and ensure the tool's shank is gripped uniformly in all three jaws
• Verify the tool's tightness, and if necessary, tighten further using the third keyhole

Handling Precautions for Chuck

• Do not tighten the chuck by holding in your hands with the motor running
• Potential injury or damage to chuck or drill can happen if you don't follow this precaution
• The key can cause injury if the motor is started with it still in the chuck
• Disconnect the power or air supply ideally, while working with the chuck

Deburring

• When holes are drilled through two sheets of material, small burrs are formed around the edges
• Chips may be pushed between the sheets, therefore it's essential to remove burrs and chips
• Removal of burrs can be achieved with a manufactured deburring tool, a countersinking tool (with very light cut) or a large drill to clear edges
• Take care to remove only rough edges and chips
• Remove chips from between sheets when drilling two or more sheets at the same time

Special Deburring Tool

• This tool deburrs holes on the exit side when standard tools can't
• It is chucked in a drill motor for rapid work
• The spring pressure holds retractable blade in place
• Push through hole and remove burrs from the exit side to use
• Draw back through the hole and remove burrs from the entry side
• Deburring tool comes in common hole sizes from 5/32 to 3/8 inch

Metal Cutting Tools

• Hand snips each have different purposes
• Straight snips cut straight lines when the distance isn't great enough for a squaring shear and cut the outside of a curve
• Other types cut the inside of curves/radii
• Snips should not be used to cut heavy sheet metal
• Aviation snips cut heat-treated aluminum alloy and stainless steel, are also adaptable for enlarging small holes
• Cut edges have small teeth for small circles & irregular outlines
• Handles are compound leverage type, enabling cutting material 0.051 inch thick
• Aviation snips come in types that cut from right to left and left to right

Punches

• Punches are used to locate centers for drawing circles
• Punches start holes for drilling
• Punches punch holes in sheet metal
• Punches transfer the location of holes in patterns
• Punches remove damaged rivets, pins, or bolts

Bending Tubes

• Care must be taken to ensure that the correct tool is used for bending tubes, depending on the diameter of the tube
• The swivel handle of larger tube benders has an angled slot that can slide outwards so that the tube can be laid in the guide groove
• After this, the swivel handle is pushed down again and the tube clamp is placed around the tube
• The left side of the swivel handle is now on the zero marking of the scale
• It is recommended to lightly lubricate the tube at the bend point before bending
• To bend, secure the tube bender with the form wheel handle in a vice
• The tube is bent by pulling both levers together
• With steel tubes, usually arc the bend further because the tube springs back slightly after bending
• Light metal tubes hardly ever exhibit this spring back
• After bending, the swivel handle is pushed up over the slot, the tube clamp is moved back and the tube is removed

Aircraft Sheet Metal Construction & Repair

• Aircraft sheet metal construction and repair involve the design, fabrication, assembly, maintenance, and restoration of structural components
• This is crucial for structural integrity, aerodynamics, and aircraft safety

Types of Aircraft Sheet Metal Structures

• Monocoque structures rely on the outer skin (or shell) to bear most the structural loads
• Monocoque structures offer lightweight and strong design without needing an internal frame
• Semi-monocoque structures utilize a stressed skin, reinforced reinforced by internal structural elements like stringers, frames, and bulkheads to maintain shape and distribute loads
• Truss structures, also known as framework fuselages, use a network of interconnected beams (trusses) to form a rigid frame, usually made of steel or aluminum tubing, and covered with a skin
• Stressed-skin wing construction involves the wing's outer skin (or covering) and internal structure working together to manage flight and ground loads
• Enhancing strength and rigidity while reducing weight is a goal of the stressed-skin construction method

Aircraft Stresses

• Tensile stress is when forces tend to stretch or lengthen the material
• Compressive stress is when to compress or shorten the material
• Shearing stress is the stress to shear the material

Properties of Materials

• Hardness of the material enables resistance to penetration, wear, or cutting action
• Strength is a material's capacity to withstand forces that deform the metal
• Elasticity is the ability of an object or material to be stretched and recover its size and shape after deformation
• Plasticity is the property of a metal which allows it to be reshaped
• Ductility allows metal to be drawn into thinner sections without breaking
• Malleability allows a material to be stretched or shaped by beating with a hammer or passing through rollers without breaking
• Toughness of a material allows it to be deformed without breaking
• Brittleness causes a material to break when deformed or hammered; it is resistance to change in the relative position of the molecules within the material
• Conductivity enables a material to transmit heat or electrical conduction
• Durability allows a material to withstand force over time

Materials Overview

• Metallic materials have or contain the nature of metal
• Non-metallic materials contain no metal
• Ferrous materials are iron or any alloy containing iron
• Non-Ferrous materials are metals which contain no iron

Materials for Sheet Metal Aircraft Construction

• Aluminum alloys are widely used in aircraft sheet metal construction for their lightweight and strength
• 2024-T3 aluminum is high strength, with good fatigue resistance, but less corrosion-resistant
• 6061-T6 aluminum has good corrosion resistance, medium strength, and is weldable
• 7075-T6 aluminum is extremely strong and used in structural components but is less corrosion-resistant
• Copper and its alloys are crucial in aircraft construction for their excellent electrical and thermal conductivity, durability, and corrosion resistance, particularly in electrical systems, wiring, connectors, and hydraulic components
• Manganese is used as an alloying element in aircraft construction materials, especially aluminum alloys, to enhance strength, enhance formability, and improve control grain size of a material

Metal General

• Metal consists of basic chemical elements with varying characteristics and properties
• The basic characteristics and properties of metal include heat-treatable, cold-workable, crystal structure, heat/electrical conductivity, light impenetrability, metallic gloss by light-reflection, and dissolvability in acids under formation of salts
• Lightweight metals, with density under 5 Kg/ dm³, are used for airframe construction
• Aluminium and Aluminum Alloys at 2.7 Kg/dm³, titanium and titanium Alloys at 4.5 Kg/dm³, and magnesium and magnesium alloys at 1.74 Kg/dm³ include three important lightweight metals in aircraft structure

Metals of Aircraft Structure

• Magnesium has a density of 1.74 kg/dm³ and a melting point of 650° C
• Silicon has a density of 2.33 kg/dm³ and a melting point of 1420° C
• Aluminum has a density of 2.70 kg/dm³ and a melting point of 658° C
• Titanium has a density of 4.50 kg/dm³ and a melting point of 1727° C
• Zinc has a density of 7.14 kg/dm³ and a melting point of 419° C
• Manganese has a density of 7.30 kg/dm³ and a melting point of 1250° C
• Iron has a density of 7.86 kg/dm³ and a melting point of 1539° C
• Copper has a density of 8.93 kg/dm³ and a melting point of 1083° C