JC Graphics flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Third-angle projection symbol
- A truncated cone shown with the small end toward the viewer on the left; it indicates views placed where the observer stands, with top above front.
- Hidden detail line
- A dashed line of medium thickness representing an edge not visible in the chosen view; dashes should meet at corners and never be used for dimensioning.
- Centre line
- A chain thin line of long and short dashes marking axes of symmetry, pitch circles, and centres of holes; it extends slightly beyond the feature outline.
- Isometric scale
- The ratio 0.816 applied to true lengths when constructing a true isometric projection; drawings made at full scale along the axes are isometric drawings.
- Auxiliary view purpose
- Projects perpendicular to an inclined face so that face appears in true shape and size, which no principal orthographic view can show.
- Section hatching convention
- Cut material is shown by evenly spaced thin lines at 45 degrees to the main axes; separate adjacent parts are hatched in opposing directions for clarity.
- Representative fraction
- The ratio of drawing length to real length, written as 1:50 or 2:1; enlargements have the second number smaller than the first.
- Dimension placement rule
- Each feature is dimensioned once, on the view that shows it most clearly, outside the outline, and never on a hidden line.
- Regular polygon angle
- Each interior angle of a regular polygon equals (n - 2) times 180 divided by n, where n is the number of sides.
- Angle in a semicircle
- Any angle subtended by a diameter at a point on the circumference is exactly 90 degrees; the converse locates a circle on a hypotenuse.
- Tangent-radius property
- A tangent to a circle is perpendicular to the radius drawn to the point of contact, giving a right angle for construction and proof.
- Parabola from a cone
- Produced when a cutting plane is parallel to one generator of the cone; the eccentricity equals one and the curve has a single focus.
- Ellipse focal property
- For any point on the ellipse the sum of distances to the two foci is constant and equals the major axis length 2a.
- Cone volume formula
- Volume equals one third of pi times radius squared times perpendicular height; the slant height is not used in the volume calculation.
- Sphere surface area
- Surface area equals 4 pi r squared, four times the area of the great circle; volume is four thirds pi r cubed.
- Cylinder development
- The curved surface unrolls into a rectangle of width 2 pi r and height h, with two circular ends attached along the top and bottom edges.
- Cycloid construction
- The path of a point on a circle rolling along a straight line; one arch spans 2 pi r and the generating circle divides it into equal parts.
- Involute of a circle
- The curve traced by the end of a taut string unwound from a circle; used for gear tooth profiles because contact remains along a straight line.
- Similar figures ratio
- Lengths scale by k, areas by k squared, and volumes by k cubed; doubling a model's dimensions multiplies volume by eight.
- Golden ratio proportion
- A division where the whole is to the larger part as the larger is to the smaller, approximately 1:1.618, often used for pleasing rectangles.
- A series sheet sizes
- A0 measures 841 by 1189 mm with area one square metre; each smaller size halves the previous area by halving the longer side.
- Title block essentials
- A reserved panel carrying drawing number, title, scale, projection symbol, material, date, and approvals so the sheet is self-identifying.
- Line width hierarchy
- Thick lines are twice the width of thin lines; typical thick values are 0.5 or 0.7 mm with thin lines at 0.25 or 0.35 mm.
- Lettering standard ISO 3098
- Specifies upright or sloped capital lettering for technical drawings, with a minimum height of 2.5 mm for legible reproduction.
- Proximity in layout
- Related items are grouped close together while unrelated items are separated, so the eye reads structure before reading detail.
- Contrast for accessibility
- Strong light-dark contrast between text and background aids legibility; red-green pairings should be avoided for colour-blind readers.
- Rule of thirds
- Dividing a frame into a three-by-three grid and placing key elements on intersections produces balanced, dynamic composition.
- Construction geometry in logos
- Symbols built from specified circles, grids, and tangents can be redrawn exactly at any size, so the design brief should list these parameters.
- First-angle symbol
- A truncated cone with the small end pointing away from the viewer on the left; views are placed on the far side of the object.
- Freehand sketching proportion
- Establish overall bounding box and centre lines first, then subdivide; checking widths against a pencil held at arm's length keeps proportions true.
- Drawing register purpose
- A log listing drawing numbers, titles, revisions, and issue dates that controls document versions across a project team.
- Tolerance notation
- Limits of size or geometric tolerances state the permitted variation; unilateral tolerance allows deviation in one direction only from nominal.