introduction to engineering graphics
TRANSCRIPT
Branch: : INFORMATION TECHNOLOGY
TOPIC : :introduction of egPresented by: Acharya Mansi Akshay Dhanani Aandhi Aasif Ankoliya RitenGuided by: Jay Shah
DRAWING INSTRUMENTSSHEET LAYOUTSCALESLINES
Engineering drawing is a technique of creating graphical representation that contains all necessary information such as dimensions, specifications and notes, using which an abstract concept can be transformed into real world object. Application of engineering drawing are valid for e.g.: Shipping industry, manufacturing, construction and many more.
Some important concept of engineering drawing is like projection. The word projection means to throw forward. It is a process of plotting an object in an imaginary plane. Projection has two types:
1. Parallel projection2. Perspective projection Each of these has further subtypes.
1. Drawing paper: The size of drawing paper should be less than drawing board and paper should be fixed properly.
2. Drawing board: It is a plane and smooth surface use for drawing purpose.
3. T-square: It is a T shape drawing tool whose edge slide along width of drawing board with the help of stop. It is useful in drawing straight line.
4. Compass: It is used for drawing circles and arcs. The divider is little different with both legs made of steel and use for transferring distance.
5. French Curves: They are used to draw irregular curves such as ellipse, hyperbola and parabola.
6. Drafter: It is useful tool for drawing parallel lines at any inclination. It has scale as well as protractor inbuilt.
7. Protractor: It is use to measure and layout angles.8. Set Square: It is also known as triangle. They comes
in flavors of 30, 60, 30 and 45, 90, 45.
Typical Drawing Equipment
Objectives in Drawing
1. Accuracy
2. Speed
3. Legibility
4. Neatness
It is useful tool for drawing parallel lines at any inclination. It has scale as well as protractor inbuilt.
They are used to draw irregular curves such as ellipse, parabola and hyperbola.
Drawing Boards
The left edge and right edge of a drawing board has a true straight edge.
For right-handed people, the left-hand edge of the board is called the working edge because the T-square head slides against it.
For left-handed people, the right-hand edge of the board is called the working edge because the T-square head slides against it.
T-Squares
The T-square is made of a long strip called the blade, fastened at right angles to a shorter piece called the head.
The drawing paper should be placed close to the working edge of the board to reduce any error resulting from the bending of the blade of the T-square.
The paper should also be placed close enough to the upper edge of the board to permit space at the bottom of the sheet for using the T-square.
Drafting tape is used to fasten the drawing paper to the drawing board.
Drawing Pencils
High-quality drawing pencils should be used in technical drawing, never ordinary writing pencils.
Many makes of mechanical pencils are available together with refill leads in all grades. Choose a mechanical pencil that feels comfortable in your hand.
HARD MEDIUM SOFT
9H 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B
Hard leads are used where extreme accuracy is required. Generally these leads are used for construction lines.
Medium leads are used for general purpose line work in technical drawing.
Soft leads are used for various kinds of art work. These leads are too soft to be useful in mechanical drafting.
Drawing Leads
The first consideration in the selection of a grade of lead is the type of line work required. For light construction lines and guide lines for lettering use a hard lead. For all other line work, the lines should be BLACK. The lead chosen should be soft enough to produce jet black lines but hard enough not to smudge.
TrianglesMost inclined lines are drawn at standard angles using the 45º x 45º triangle and the 30º x 60º triangle.
In addition to drawing angles of 90º, 45º, 30º, and 60º, triangles can be combined to draw angles of 15º increments.
ScalesScales are instruments used in making technical drawings full size or at a given reduction or enlargement.
Types of scales include metric scales, engineers’ scales, decimal scales, mechanical engineers’ scales, and architects’ scales.
Scales are usually made of plastic or boxwood and are either triangular of flat in shape.
Margin: Margin is provided in the drawing sheet by drawing margin lines. Prints are trimmed along this lines.
Border lines: Clear working space is obtained by drawing border lines. More space is kept on the left-hand side for the purpose of filling or binding if necessary.
Borders and frames: SP:46(2003) recommends the borders of 20mm width for the sheet sizes A0 and A1, and 10mm for sizes A2, A3, A4 and A5.
Title Block: Space for title block must be provided in the bottom right-hand corner of the drawing sheet. The size of the title block as recommended by the B.I.S is 185mm*65mm for all designations of the drawing sheet. All title blocks should contain at least the particulars as shown in the figure:
Main Line Types
Lines
Hidden Lines
Center Lines
Dimension Lines
Extension Lines
Leader LinesCutting Planes
Section Lines
Phantom Lines
Viewing Planes
Break Lines
Visible Lines
Dimension Lines• Thin lines capped on the ends with arrowheads and
broken along their length to provide a space for the dimension numeral.
• They indicate length.
Center Lines• Thin line consisting of alternating long and short
dashes.• Used to represent the center of round or cylindrical
features, or the symmetry of a feature.
Section Lines
• Thin line usually drawn at a 45 degree angle.• Indicates the material that has been cut through in a
sectional view.
Section Line
Hidden Lines• Light, narrow, short, dashed lines.• Shows the outline of a feature that can not be seen in
a particular view.• Used to help clarify a feature, but can be omitted if
they clutter a drawing.