3-2 Layout

Circumference

The distance around the outside circle

Dividers

Used for laying out arcs or circles on metal, transferring measurements and to divide lines in equal parts

Orthographic Drawings - Basic Views

- Front view: Always drawn first. The view is determined by the side which shows the most characteristic shape and avoids unnecessary hidden surfaces. All other projections come from this view - Right side view: Located to the right of the front view - Left side view: located to the left of the front view - Top view: located directly above the front view - Bottom view: located directly below the front view - Rear view: may be shown to the outside of the bottom, top, or either side view

Proper Care of Tools and Precautions

- Keep tools sharp - Protect the points - Clean and lubricate tools occasionally - Inventory the tools before, during, and after every job - Never carry tools in pockets or throw tools - Beware of sharp points and keep tools in the toolbox unless they are being used

Steel Rule

A basic measuring tool with four sets of graduations, one on each edge of each side. On one edge, each inch is divided into eight equal spaces, each representing 1/8 inch. The other edge of this side is divided into sixteen equal spaces, each representing 1/16-inch. The opposite side is similarly divided into thirty-two and sixty-four spaces per inch, and it is common practice to number every fourth division for easier reading

Flat Pattern Layout

A drawing of an object that has been rolled, folded, or a combination of both, and then spread out on a plane or flat surface. Used as a guide or pattern, which is transferred to a piece of sheet metal to be cut and formed

Reference Line

A perpendicular line made from the reference edge, 90 degrees to reference edge (used for measuring vertical line location). Reference lines are made by use of a combination square and scribe

Scribe

A sharp steel pick, used like a pencil for marking cut lines only

Reference Edge

A straight edge of the metal from where measurements are taken (used for measuring horizontal line location)

Neutral Axis (NA)

An imaginary line near the center of the metal. Always remains constant and will never shrink or stretch.

Mold Line (ML)

An imaginary line that runs between mold points

Sectional Views

Clarify internal or hidden features

Combination Square

Consists of a steel rule with an accurately machined head for measuring any degree of angle (with a protractor). Most combination squares provide for measuring 45 degrees and 90 degrees

Isometric Drawings

Drawings that give a three-dimensional or a pictorial view of an object. Vertical lines are shown in a vertical position. Horizontal lines are drawn at an angle of 30 degrees to the horizontal. These drawings may be dimensioned. Dimensions are all drawn to the same scale. Gives a picture of the completed project, and it clarifies orthographic drawings

Orthographic Drawings

Drawings that show the exact shape of an object through the use of different views.

Bend Allowance (BA)

Figured along the neutral axis. The amount of metal used to make a bend or the distance between the bend tangent lines

Flat (F)

Flat portion of a formed part. The portion of a formed part not included in a bend

Angles

Formed by drawing two straight lines that meet or intersect at a common point

Visible Lines

Heavy unbroken lines that indicate the outer edges of an object

Arcs

Incomplete circles, comprised of less than 360 degrees

Cutting or Viewing Plane

Indicated by thick solid lines with arrows that show the direction in which the section or plane is to be viewed

Offset Cutting Plane

Indicates by thick, short dashes that show offset with arrows to show direction viewed

Bend Tangent Line (BTL)

Indicates the beginning and end of a bend

Cut Line

Indicates the exact amount of metal required to make a part and is always drawn with a scribe

Parallel Lines

Lines equal in distance along their entire length and never cross

Mold Point (MP)

Located at the intersection of extension lines outside the formed part

Break Lines

Long Breaks - thin, solid, ruled lines, with freehand zigzags Short Breaks - thick, solid, freehand lines that reduce the size of the object drawn

Tapered Projects

Measurements use a centerline rather than a reference edge

Phantom or Datum Lines

Medium lines in a series of one long dash and two short dashes, evenly spaced and ending with a long dash, that indicate alternate positions of parts, repeated detail, or the relative position of absent parts

Hidden Lines

Medium lines with short, evenly spaced dashes that indicate the concealed edges

Station Diagrams

Normally orthographic views of fuselage, wing, or empennage showing location of all structural components

Base Measurement (BM)

Outside dimension of a formed part or overall dimension of a formed part

Phantom Views

Shows the alternate position of a part or the position of a missing part

Schematic Diagrams

Shows the relation of parts within a system, how they are connected, and the arrangement of the components

Auxiliary Views

Shows the true shape and length of an inclined surface or other special features

Setback (SB)

The distance from the bend tangent line to the mold point

Radius

The distance from the center of a circle to the outer edge

Diameter

The distance, measured through the center, from the outer edge to the opposite outer edge

Tangent

The point where a straight line touches an arc or a circle but does not pass through

Bend Radius (BR)

The radius of a bend and is always measured to the inside unless otherwise stated

Leader Lines

Thin lines ending in an arrow or dot which indicate a part, dimension, or other reference

Dimension Lines

Thin lines ending with arrows that indicate the measured distance

Centerlines

Thin lines, made of long and short dashes, alternately spaced, and consistent in length. The lines always begin and end with a long dash

Extension Lines

Thin unbroken lines that indicate the ends of a measured distance

Bend Line

Used as a guide for positioning the metal in the brake and is located on a flat layout, one bend radius from the bend tangent line. The bend line lines up with the nose of the upper jaw of the brake. Bend lines are always drawn with a pencil and indicated with an "X"

Prick Punch

Used for reference marks, used to make a light mark for hole centers and center of arcs. The point is sharpened to a 60 degree angle

Drift Punch

Used to finish driving out a bolt, pin or rivet from a hole. Always use the largest diameter drift punch that will fit the hole. These punches have flat points, never edged or rounded

Center Punch

Used to mark hole locations for drilling, prevents the drill from wandering. The point is sharpened to a 90 degree angle

Exploded Views

Used to show relative location of parts. Parts are spread out in a line to show clearly each part's relationship to the other parts

Alignment Diagrams

Used when an alignment check on an aircraft is performed. Measurements are given from point to point with special instructions, and special views are used to clarify points

Pencil Compass

Used when drawing arcs, curves, circles, and when bisecting lines

Triangles

Used when drawing vertical or diagonal lines. A 45 degree triangle has two angles of 45 degrees and one angle of 90 degrees. A 30-, 60-, and 90- degree triangle has one angle of 30 degrees, one angle of 60 degrees, and one angle of 90 degrees