LINES in Drawing

Various types of lines used in general engineering drawing are shown below  

Types of Lines:

Solid Lines:

          These are the most commonly used lines in Engineering Drawing. They represent the edges, surfaces, or Outlines of an object, Solid lines are typically used to depict the visible parts of an object.

Thin Lines:

          These are used for various purposes, such as dimension lines (showing the size of an object), Extension lines (extending a line on an object to aid in dimensioning), and leader lines (connecting a dimension number or note to a feature).

Dashed Lines:

Also known as hidden lines. Dashed lines are used to represent edges or surfaces that are not visible in a particular view. For example, they might show the edges of an object that are hidden behind other parts.

Dotted Lines:

          Often used for center lines or symmetry lines, dotted lines indicate the geometric centre of an object or a part. They can also be used to represent the path of movement for moving parts.

Phantom Lines:

          These are used to indicate alternate positions of a moving part or adjacent positions of related parts.

Centre Lines:

          Parts with holes and symmetrical features can be shown by using centre lines. Symmetry can reduce the number of dimensions in a drawing and make it more visually appealing, making it easier for the reader to comprehend.

Dimension Lines:

          Extension lines are used to describe the data being collected. Two arrow heads separate the extension lines on the dimension line from the measurement above (or inside, as shown in the image).

Cutting plane Lines:

          The cutting plane lines illustrate the path of the cutout in a cutout view. The A-A cutting line may be seen here bringing both types of holes into view.

DRAWING SHEET

          Drawing sheet is the medium on which drawings are prepared by means of pencils (or) pen. Drawing Sheets are available in many types and sizes (like A4, A3, A2, A1, A0 etc.,). In general we prepare pencil-drawings, for this the paper we selected should be tough, strong and smooth surface. It's thickness should be uniform and as white as possible. When the rubber eraser is used on it, fibres should not disintegrate. Good quality of paper should be selected for drawings which are to be inked and preserved for a long time. It should be such that the ink does not spread. Thin and cheap quality paper may be used for drawings from which tracings are to be prepared.

          The Standard sizes of drawing papers: ~ recommended by the Bureau Of Indian Standards (B.I.S) are given below

While in the drawing sheet .. first we have to draw border lines and title box and then we have to start drawing

Title block:

          The document's title in an engineering drawing block is found in the bottom right-hand corner of the page. Also known as the information blocks. It includes the part name, the names of the people who worked on the part (design, checking, and approval), the name of the company, the drawing number, ad other relevant information.

          In addition, it includes technical details such as the measurement units, the angle of projection, the surface polish criteria, the scale, and the material of construction. Title blocks are used for a better understanding of all parts of technical drawing. 

T-Square

          A T-square (T-shaped ruler) is a tool used in hand-drawings. Generally it is made up of hard quality wood. It consists of two parts - The stock and The Blade  jointed together at right angles to each other by means of screws and pins.

          The stock is placed adjoining the working edge of the board and is made to slide on it as and when required. The blade lies on the surface of the board. Its distant edge which is generally bevelled, is used as the working edge and hence, it should be perfectly straight. The nearer edge of the blade is never used. The length of the blade is selected so as it suit the size of the drawing board. Now-a-days T-Square is also available of celluloid (or) plastic with engraved scale.

Uses:

     (i) The T-Square is used for drawing horizontal lines. The stock of the T-Square is held firmly with the left hand against the working edge of the board, and the line is drawn from left to right as shown in fir 1.3. The pencil should be held slightly inclined in the direction of the line (i.e., to the right) while the pencil point should be as close as possible to the working edge of the blade. Horizontal paralleled fines are drawn by sliding the stock to the desired positions Fig. 1-3.

     (ii) The working edge of the T-Square is also used as a base for set-squares to draw vertical, inclined or mutually parallel lines. A pencil must be rotated while drawing lines for uniform wear of lead. The T-Square should never be used on edge other than the working edge of the board. It should always be kept on the board even when not in use.

     (iii) Testing the straightness of the working edge of the T-Square: Mark any two points A and B (fig 1.4) spaced wide apart and through them, carefully draw a line with the working edge. Turn the T-Square upside down as shown by dashed lines and with the same edge, draw another line passing through the same two points. If the edge is defective the lines will not coincide. The error should be rectified by planing or sand-papering the defective edge.

DRAWING BOARD

 DRAWING BOARD:

Drawing board is rectangular in shape and is made of strips of well-seasoned soft wood about 25 mm thick. It is cleated at the back by two battens to prevent warping. One of the edges of the board is used as the working edge, on which the T-square is made to slide. It should, therefore, be perfectly straight. In some boards, this edge is grooved throughout its length and a perfectly straight ebony edge is fitted inside this groove. This provides a true and more durable guide for the T-square to slide on.

Drawing board is made in various sizes. Its selection depends upon the size of the drawing paper (like A4, A3, A2, A1, A0 etc) to be used. The sizes of drawing boards recommended by the Bureau of Indian Standards (IS:1444-1989) are tabulated in table.

 For use in schools and colleges, the last two sizes of the drawing boards are more convenient. Large-size boards are used in drawing offices of engineers and engineering firms. The drawing board is placed on the table in front of the student, with its working edge on his left side. It is more convenient if the table-top is sloping downwards towards the student. If such a table is not available, the necessary slope can be obtained by placing a suitable block of wood under the distant longer edge of the board.