UNIT 3: REPRESENTATION OF TECHNOLOGICAL PROJECTS

DimensioningTechnologies 1 ESO

gabriela-teacher.blogspot.com

What is “dimensioning”?To dimension is to indicate the measurements of a real object in a drawing.

Why do we dimension drawings?

We dimension to give information:-To someone who will manufacture or build our design.- To give precise information to other people.

What is important when we dimension a drawing?

Our style when we dimension a drawing has to be:-Understood all over the World.- Simple.- Clear.

So, that is why, a comittee created, years ago, an

International set of rulesfor dimensioning.

Basic Elements

REFERENCE OREXTENSION LINE

DIMENSIONDIMENSION LINE

ARROW HEAD

-Don’t write units (mm, cm…), only numbers.-Always above the line.

-Soft thin line.-It has to extend 5mm longer than the dim. line.

-Technical and simple.-They have to touch the reference line.

-Thick black line.-It has to touch the reference line.-Leave enough space from the object.

Rule 1

No missing dimensions.X √

Rule 2

No unnecessary dimensions.

X √

Rule 3Try to be tidy: arrange your dimensions along common

lines.X √

No dimensions inside the object or coinciding with its

contour lines.

Rule 4

X √

Two dimension lines must never cross.

Dimension and reference lines must not cross.

Rule 5

X √

X √

How to dimension circles or arcs

We use the symbols R (radius) or Ф (diameter).

We mark with dashed lines the two main diameters (vertical and horizontal) and the center of the circle or arc.

If you want to practise…

… dimension these objects!! You can copy them on your notebook and think that each little chart represents 10 mm in reality.

Show them to the teacher for corrections and extra mark!!