By: Mr. Lua

Alphabet of Lines When 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 Lines Construction Used to lay out drawings. Guide Used usually when lettering to create the information boxes.

Border Line Is the heaviest or thickest line used in sketching.

Object Lines Thick line but slightly less thick than a boarder line. This line indicates the visible edges of the part.

Hidden Lines Are used to show the hidden features of a part. Dashes of (1/8 in) and (1/16 in)

Extension Line These are as think as dimension lines and indicate points from which the dimensions are taken.

Dimension Line Generally 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.

Centerline Made 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 Lines Indicates 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 Line Used when drawing inside features of an object to indicate the surfaces exposed by the cutting-plane line.

Phantom Line Used 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