ISO 5455 recommended scales for technical drawings

The scales recommended for technical drawings, and how the scale is designated.

ISO 5455:1979, 5.1, table of recommended scales; kinds from 2.2 to 2.4

Designation and inscription

• ratio = length on the original drawing / real length of the object (ISO 5455:1979, 2.1). The scale of a print may differ from that of the original drawing (2.1, NOTE).
• SCALE 1 : 1 for full size; SCALE X : 1 for enlargement; SCALE 1 : X for reduction — ISO 5455:1979, clause 3
• If there is no likelihood of misunderstanding, the word SCALE may be omitted.
• The scale used on the drawing shall be inscribed in the title block (4.1). Where more than one scale is used, only the main scale goes in the title block; every other scale goes next to the item reference number of the part, or next to the reference letter of the detail view or section (4.2).
• For special applications the range may be extended in either direction, provided that the scale is a recommended scale multiplied by a whole-number power of 10. In exceptional cases, where for functional reasons the recommended scales cannot be applied, intermediate scales may be chosen. — ISO 5455:1979, 5.1, NOTE

Notes from the data file

• The standard prints the ratio with spaces around the colon ('1 : 2'); ids here omit the spaces. MechPilot shows 'SCALE 1:2' / 'SCALA 1:2' in the UI and writes the standard's form on the sheet.
• ISO 7200:2004 does not list scale among the title-block data fields (it is 'presented outside the title block only when used', ISO 7200:2004, clause 4), while ISO 5455:1979, 4.1 asks for the main scale in the title block. MechPilot follows ISO 5455 and adds a scale field next to the ISO 7200 fields.
• Detail views drawn to a larger scale for details too small to dimension in the main view: 5.3. A full-size view may be added to a large-scale drawing of a small object: clause 6.