Teknologi Dan Rekayasa TECHNICAL DRAWING

BASIC RULES OF DIMENSIONING Objective : After studying this lesson, the students should be able to : 1. explain the basic rules of dimensioning 2. apply the basic rules of dimensioning on the technical drawing Teknologi dan Rekayasa

BASIC RULES OF DIMENSIONING Dimensioning is accomplished according three different method. First the principal dimensions are required (length, width and thickness), to enable material corresponding to the basic shape of the component to be obtained from the stores. These dimensions are termed : Overall dimensions Progressive dimensions Chain dimensions Teknologi dan Rekayasa 3

Overall dimensions These serve primarily for dimensioning the overall length, width, height or diameter. 5 thick 20 Ø 25 55 25 4

Progressive dimensions These method is used where dimensions are given from definitive datum surfaces or datum edge. 45 50 Datum edge Ø 25 Ø 10 5 10 10 15 Datum edge These datum surfaces (datum line) must first be machined (filled, turned, etc). The dimensions can than be built up step by step. 5

Chain dimensions This method is used where a series of associated dimensions, such as, for example, the width of slots or collars and their position, and the width a number of splines. 10 5 5 NOTE : Always enter the dimension for the slot width on one view Teknologi dan Rekayasa 6

Chain dimensions If these three methods of dimensioning are combined, they provide a complete system of dimensions. 5 50 Ø 25 Ø 22 Ø 10 Ø 15 20 45 5 5 thick 25 5 15 10 10 55 Teknologi dan Rekayasa 7

Chain dimensions Dimensions of less than 10 mm are indicated with the arrows outside. Those greater than 10 mm with the arrows inside. If several dimensions less than 10 mm occur in a row (dimension chain), Dots can be used instead of arrows. 5 10 Teknologi dan Rekayasa 8

RULES FOR DIMENSIONING 1. To place of dimension line. Right Wrong 2. To insert chain dimension. Teknologi dan Rekayasa 9

RULES FOR DIMENSIONING 3. To insert parallel dimension. 4. To insert combined dimension. Teknologi dan Rekayasa 10

RULES FOR DIMENSIONING 5. To insert the dimension in line Teknologi dan Rekayasa 11

RULES FOR DIMENSIONING 6. To insert the dimension with coordinates Teknologi dan Rekayasa 12

RULES FOR DIMENSIONING 7. To insert the dimension in the drawing arrangement Teknologi dan Rekayasa 13

THE END Teknologi dan Rekayasa