Welding Construction Lines : Welding Symbols
a. Full Lines (A, fig. 3-1). Full lines represent the visible edges or outlines of an object.
b. Hidden Lines (A, fig. 3-1). Hidden lines are made of short dashes which represent hidden edges of an object.
c. Center Lines (B, fig. 3-1). Center lines are made with alternating short and long dashes. A line through the center of an object is called a center line.
d. Cutting Plane Lines (B, fig. 3-1). Cutting plane lines are dashed lines, generally of the same width as the full lines, extending through the area being cut. Short solid wing lines at each end of the cutting line project at 90 degrees to that line and end in arrowheads which point in the direction of viewing. Capital letters or numerals are placed just beyond the points of the arrows to designate the section.
e. Dimension Lines (A, fig. 3-1). Dimension lines are fine full lines ending in arrowheads. They are used to indicate the measured distance between two points.
f. Extension Lines (A, fig. 3-1). Extension lines are fine lines from the outside edges or intermediate points of a drawn object. They indicate the limits of dimension lines.
g. Break Lines (C, fig. 3-1). Break lines are used to show a break in a drawing and are used when it is desired to increase the scale of a drawing of uniform cross section while showing the true size by dimension lines. There are two kinds of break lines: short break and long break. Short break lines are usually heavy, wavy, semi-parallel lines cutting off the object outline across a uniform section. Long break lines are long dash parallel lines with each long dash in the line connected to the next by a “2” or sharp wave line.