Engineering Drawing and Drafting
Engineering Drawing and Drafting tests whether you can communicate a three-dimensional object on a sheet using Indian Standard conventions. The paper usually pairs a drawing-board exercise (orthographic views, sections, development, isometric) with short-answer theory on instruments, scales, projection symbols and IS codes.
Line work and lettering
- Visible outline: continuous thick, about 0.6 mm.
- Hidden edge: short dashes, thin, evenly spaced; never drawn through a dimension.
- Centre line: long-short chain, thin, extended 2-3 mm beyond the feature.
- Dimension, extension and hatching lines: thin continuous; arrowheads touch the extension line.
- Lettering per IS 9609: single-stroke italic capitals, height-to-width ratio about 7:5 for titles.
Scales
A scale is the representative fraction (RF) = drawing length / actual length, both in the same unit. An RF below 1 is a reducing scale. A plain scale reads to one decimal place; a diagonal scale reads to two.
Worked example
A road 4 km long is drawn 8 cm long. RF = 8 cm / (4 x 100000 cm) = 8/400000 = 1:50 000. A scale 5 m long represents 5 x 50 000 cm = 2.5 km; divide it into five major parts of 0.5 km and subdivide the first part into ten for 50 m readings.
Projection
India follows first-angle projection (IS 696): the object lies between observer and plane, so the top view is placed below the front view and the left-side view appears on the right. The symbol is a truncated cone with the smaller circle nearer the front view.
Traps
- Swapping the first-angle and third-angle symbols.
- Drawing hidden lines thick, or taking them through dimension text.
- Using true length as the isometric length; the isometric scale shortens by 0.816.
- Hatching a section without the 45 degree lines, or in the same direction on two adjacent parts.