cad-site: BORDER AND FRAMES

Borders enclosed by the edges of the trimmed sheet and the frame, limiting the drawing space,

should be provided with all sheet sizes. It is recommended that these borders have a minimum

width of 20 mm for the sizes A0 and A1 and a minimum width of 10 mm for the sizes A2, A3

and A4 (Fig.). A filing margin for taking perforations, may be provided on the edge, far left

of the title block.

Centring Mark

Four centring marks may be provided, in order to facilitate positioning of the drawing when

reproduced or microfilmed. Two orientation marks may be provided to indicate the orientation

of the drawing sheet on the drawing board

It is recommended to provide a figure-less metric reference graduation, with a minimum length

of 100 mm and divided into 10 intervals on all the drawing sheets (Fig. ) which are intended

to be microfilmed. The metric reference graduation may be disposed symmetrically about a

centring mark, near the frame at the border, with a minimum width of 5 mm.

The provision of a grid reference system is recommended for all the sizes, in order to permit

easy location on the drawing of details, additions, modifications, etc. The number of divisions

should be divisible by two and be chosen in relation to the complexity of the drawing. It is

recommended that the length of any side of the grid should not be less than 25 mm and not

more than 75 mm. The rectangles of the grid should be referenced by means of capital letters

along one edge and numerals along the other edge, as shown in Fig. 2.4. The numbering direction

may start at the sheet corner opposite to the title block and be repeated on the opposite sides.

Trimming marks may be provided in the borders at the four corners of the sheet, in order to

facilitate trimming. These marks may be in the form of right angled isosceles triangles or two

short strokes at each corner (Fig.).