dimensioning
accurate notation of measurement in technical drawing
requires careful consideration of many aspects of techinical drawing and a comprehensive understanding of the manufacturing or buiding process
line types
different line width, weights (darkness or lightness), and patterns are used within technical drawing
Primary lines
Define the object which is the most important item on the sheet
heaviest, darkest line, H,HB 0.7mm
Secondary lines
Information about the primary object
dimensions and callouts
H, H2 0.5mm or 0.3mm
Supplementary lines
material designations, pochè, construction lines, guidelines
4H,6H 0.3mm
frame (border) drawing line
is often a double line or wider than all the other
difference in notations millimiters and inches
Both uses for angles: degree, minutes and seconds.
Millimiter notation:
put zero before decimals
omit trailing zeroes
use comma and spaces
Inch notation:
omit zero before decimals
use same number of zeroes as the tolerance
don’t use comma and spaces
Hidden line
hidden lines are only provided if they add clarity to the drawings.
- always use full dash
-begin and end with a full length dash
do not cross two dashes
Leader lines
estabilish a connection between a graphical representation of an item and some text
- should be angles from the item being notated or called out
- point with an arrow or end with a dot
- tehy continue at an angle, then take a single short turn to the horizotal note
dimension line
are lines used for dimensioning, standardized line types, ends with arrow or heavy dark circle
dimension
“numerical value” or mathematical expression provided in appropriate units of measure and used to define form, size, orientation, or location of a feature or part.
- always given in real world measurements or 1:1 scale
- dimensions carry legal importance in drawing interpretation
Priority in dimensioning
- written word
- numerical notation
- drawn line
datum
A datum is the “theoretically perfect” or ideal reference point from which all measurements and tolerances are taken
