Dimensioning

General Principles

A drawing should provide a complete set of sizes for making a component.

Dimensions provide information on a drawing such as -

• Angles
• Diameters
• Lengths
• Positions

Dimensioning Standards

A - The drawing outline should be drawn with 0.7mm thickness.

B - Dimension and projection/extension lines are thin continuous lines 0.35mm thick.

C - All dimension lines are clearly placed outside the outline of the drawing.

D - The projection lines should not touch the drawing but a small gap should be left.

E - The projection lines should continue past the dimension line.

F - Arrowheads should be triangular and of uniform size and shape and filled in.

G - Arrowheads must touch the projection line to which they refer.

H - Begin by dimensioning the view which gives the clearest understanding of the component shape. 

I - Place dimensions outside the shape of the component wherever possible.

J - Position the shortest dimension nearest to the component to prevent dimension lines crossing.

K - Use a similar spacing between dimension lines to ensure a neat diagram.

L - Measure horizontal sizes from left to right and write the distance on top of the dimension line.  Angled sizes are shown in a similar manner to horizontal sizes.

M - Measure vertical sizes from bottom to top and write the distance vertically to the left of the dimension line.

N - Small sizes are shown with the arrows placed outside.

O - Place the largest sizes on the outside of the dimensional grid.

P - Sizes from a datum line are logically set out.

Dimensioning Circles

Dimension circles as shown. Holes are always dimensioned as diameters.

Dimensioning Angles 

Dimension angles as shown.