Technical Drawing Standards
Norms for Graphic Representation
A technical drawing is the graphic representation, clear, correct, and precise, of a piece on paper. It should be sufficient to fully define clear forms, not collecting unnecessary data.
Drawing Classes
- Design conception: Sketch or schema drawing.
- Definition drawing: Design and manufacturing.
Line Types
Drawings use shapes and lines of varying thickness, as applicable:
- Full line
- Dashed line
- Dash-dotted line
- Freehand line
Drawing Elements in Industry
Its purpose is to inform the dimensions of pieces or the assembly.
Bounding elements:
- Dimension line
- Dimension line arrows
- Auxiliary reference lines
- Dimension figures
- Bounding signs
Rules for Using Auxiliary Elevation Lines
When drawing a dimension line or an auxiliary dimension line, you must take into account a number of basic rules that need to be applied to make correct bounding.
- The line can be crossed with picture lines, but not with dimension lines.
- Dimension lines should not be used as auxiliary lines.
- Avoid intersecting dimension lines.
Profiles – Bounding and Bent in Orthogonal
In industrial design, pieces are represented through their orthogonal projections, using projection planes. This method is also known as the “box” or “bucket” method.
Perspective
Drawing in perspective is representing a body through a single view or projection, so that the three dimensions can be seen. This enables a more rapid and easy interpretation.
- Axonometric system
- Cavalier perspective
Sketch
This is called a “sketch” when the drawing is made quickly, freehand, and in pencil. It can be a dihedral projection or in perspective, detailing all its forms and dimensions for manufacturing.
Steps:
- Pre-examination of the part
- Freehand visualization of the piece
- Making the set
- Termination of the measurements
All measurements on the sketch must be indicated by figures (in mm) placed on dimension lines.
Sections and Material Representation
A shear section is an imaginary object cut through one or several planes, perpendicular or parallel to the drawing surface. This allows a clear and exact representation of the internal shape of the object or indicates its size.
Classes of Cuts
The most common cut types are:
- Total cut
- Half cut
- Partial cut
Striped Sections
Cut parts, regardless of the material, are scratched with fine lines forming a 45° angle with respect to the contours or the main axis. The separation should be 1.3 to 3mm.
Material Representation in Sections
There are special cases in which, rather than fine lines with uniform separation, other methods are used, or even deleted and replaced by colored areas.
Surface Finish
In manufacturing, assembly, or cut drawings, besides the representation, bounding, sections, etc., it is necessary to specify the surface finish or the degree of finish of the pieces.
Symbols Used in Surface Finish Indication
The base symbol is formed by two equal strokes, with an inclination of 60°.
Surface Areas Considered
Depending on the surface aspect, consider the following types of surfaces:
- Rough surfaces
- Machined surfaces
- Treated surfaces
Conventional Specification of Surfaces
The superficial signs listed below must be used in the drawing, primarily indicating the class of surface, with no relation whatsoever with the machining process that will be used in the workshop. Conventional signs indicate surface qualities (rough or improved) and the available machining.
Surface Qualities
They are represented by several conventional sections to specify the degree of uniformity.