Roymech engineering encyclopedia

Drawing Guide first & third angle projections

Solid Print 3D

Drawing Guide


First angle and third angle projection methods are acceptable.

The symbol identifying the type of projection used should be placed in a space provided in the drawing block

Views Using Reference Arrows.

Principal View

The principal view on which all of the other views are based should be selected as being the most informative. This may be the view which is most recognisable during manufacture or use. i.e. the front view of a house or the side view of a car.

Lines Used on Drawings..
Line Types
Line Description.......... Application
Continuous Thick Outline
Continuous Thin Intersection.. Dimension.. Projection
Leader.. Hatching
Continuous Freehand Limits of Partial or interrupted view
Continuous Thin
With Zigzags
Shortened Sections
Dashed Thick Hidden Outlines
Hidden Edges
Dashed Thin Hidden Outlines
Hidden Edges
Chain Thin Centre lines
Lines of Symmetry
Chain Thick Special Surfaces
Chain Thin
Thick ends
Cutting Planes
Chain Thin
Centroidal Lines
Initial Outlines Prior to Forming /Machining


Line Thicknesses

Two thicknesses of line should be used on a drawing.  The "thick" line should be at least twice as thick as the "thin" line.  The thickness of the line should be based on the sizes... 0,18mm 0,25mm 0,35mm 0,5mm 0,7mm 1,0mm 1.4mm and 2mm

Line spacing

The minimum space between parallel lines should always be greater than twice the thickness of the heaviest line.

Leader Lines

Leader Lines terminate

  • With a dot if they end within the outline of the item being identified.
  • With an arrow if they end on the outline
  • Without a dot or an arrow when pointing at a dimensions line


Lettering should all be in capitals and underlining should be avoided.  The lettering size should be at least 3,5mm on the finished drawing/ plot(A0 ,A1).  For larger sized lettering such as the drawing number and title in the title block 5mm is used.   Details of the lettering is found on webpage Lettering .  Smaller lettering sizes are acceptable on the smaller drawing sheet sizes A2, A3, A4 (2,5mm and 3,5mm respectively)

With the normal paper in landscape orientation and the title block on the bottom right and side, notes to be parallel with the bottom edge.

General notes shall be normally grouped together.   Notes related to specific views may be located adjacent to the view.

The minimum letter sizes are specified to meet the requirements of reading microfilm copies of drawings.    This requirement is specified in BS EN ISO 6428 .


Hatching is used to show areas of sections.

In case of large areas the hatching may be limited to a zone following the contour of the hatched area