Drafting BackgroundBy: Mr. Lua

Alphabet of LinesWhen viewing mechanical drawings you will

find several lines.This is simply reference system used to

remember different types of lines.Will focus on 10 specific most common ones.

Construction and Guide LinesConstruction

Used to lay out drawings. Guide

Used usually when lettering to create the information boxes.

Border LineIs the heaviest or thickest line used in

sketching.

Object LinesThick line but slightly less thick than a

boarder line. This line indicates the visible edges of the part.

Hidden LinesAre used to show the hidden features of a

part.Dashes of (1/8 in) and (1/16 in)

Extension LineThese are as think as dimension lines and

indicate points from which the dimensions are taken.

Dimension LineGenerally ends with an arrowhead at the

ends. Usually placed between two extension lines,

with a break usually at the center to place the dimension value.

CenterlineMade of alternate long and short dashes with

spaces between them.Long (3/4 in to 1 1/12 in)Short (1/8 in)Dashes (1/16 in)

Cutting-Plane LinesIndicates where an obeject has been cut to

show interior features. Two types used:

1/4 in dashes with 1/16 in spacing A long dash (3/4 in to 1 1/2 in) then two short

dashes (1/8 in) and spacing of 1/16 in

Section LineUsed when drawing inside features of an

object to indicate the surfaces exposed by the cutting-plane line.

Phantom LineUsed to show alternating positions of a

moving part, repeated details or the path of motion of an object.Consists of:

Dashes (3/4 in to 1 1/2 in) separated by two short lines of 1/8 in