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LOCATING AND SETTING OUT. ENG 205 CE-ME-MECE-MSE.
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LOCATING AND SETTING OUT ENG 205 CE-ME-MECE-MSE
A running dimension is a dimension that is taken from one end of a structure and provides multiple points in an increasing fashion.The dimension itself has one extension line, one arrow head and the numerical value of the item being dimensioned.Using running dimensions decrease the chance of making a mistake.
Chain dimensioning is where each point is measured to the next. E.g. Point B is measured from Point A, Point C is measured from Point B, and so on. Chain dimensioning increases the chance of accumulating a tolerance error as each measurement relies on the accuracy of the previous measurement.
Centre refers to the middle of an item. The centre of a circle is the exact point in the middle. A centre line runs directly through the middle of a component. Centreline Centre
Reference point: A point to which other points, lines, and so forth are referred, usually in terms of distance or direction, or both.Reference points can be used to locate - discover the exact position of something – points on components. *The red reference points are used in order to locate the tree and the square.
Offset (n): A short distance measured at a right-angle to (90 degrees to) the centreline. * These 4 points are offset r from the point in the middle.
Vocabulary items • Perpendicular (adj.): at an angle of 90° to another line or surface. E.g. Two perpendicular lines form a right angle. • Intersect (v): (of lines, roads, etc.) to meet or cross each other. E.g. In the end, the path intersected with a busy road. • Set out (v): to mark the position of something on a map or plan, etc. E.g. Coordinate dimensions help engineers set out sth on a drawing.
Vocabulary items • Tape measure: a long strip of plastic, thin metal, or cloth that has measurements marked on it and is used for measuring the length of something.
Vocabulary items • Theodolite (n): a piece of equipment, used for measuring horizontal and vertical angles. • Diagonal (adj.): straight and sloping, so that it is neither horizontal nor vertical.
Read part B in your book and answer the following questions. • What are grids used for? Try to explain the features of a grid in your own words. Grid is a pattern of regularly spaced horizontal and vertical lines forming squares on a map, or a chart, used as a reference for locating points.These horizontal and vertical lines have numbers and letters and they are all parallel with one another, and lettered lines are perpendicular to (90 degrees to) the numbered lines.
How does the site engineer set out the opening? He/she squares off the gridlines and then measures along these lines by using a tape measure. • What are diagonal measurements used for? Diagonal measurements are used to double-check dimensions in the sketch.
EXERCISES & OVER TO YOU