2 Blue Print Review

Blue Print Reading Review

Understanding blue prints is a vital skill in the metals industry. Whether it be as a structural welder, pipe fitter, or quality control, this is the language that is universal for all individuals involved in a project.

This chapter is here to recap some line types as well as visualizing blue prints and plans.

Line Types

1. Object Line

A visible line is a thick line, without breaks, that indicates all edges and visible surfaces of an object. An object line may also be called a visible line.


2. Hidden Line

A hidden line is a medium weight line, made of short dashes, to show edges, surfaces and corners which cannot be seen. Sometimes they are used to make a drawing easier to understand. Often they are omitted.


3. Section Line

Section lines are used on a drawing to show how an object would look if it were sectioned, or cut apart, to give a better picture of shape or internal construction. Section lines are very thin (size), and are usually drawn at an angle of 45 degrees. They show the cut surface of an object in a sectional view. Sections and section lines will be explained in BPR 7.


4. Center Line

Center lines are used to indicate the centers of holes, arcs, and symmetrical objects. They are very thin (size), long-short-long kinds of lines. (More detail needed?)


5. Dimension Line

Dimension lines are thin lines with  a break for entering a measurement of some sort. The ends of the lines will also have an arrow head pointing to an extension line (below.)


6. Extension Line

Extension lines are also thin lines, showing the limits of dimensions. Dimension line arrowheads touch extension lines.


7. Leader Line

Leaders are more thin lines used to point to an area of a drawing requiring a note for explanation.


Visualizing parts

As a welder it is imperative that you can visualize the part you are building from the print. This is not always an easy task. Prints may have a variety of parts or are not detailed as well as they should be but being able to distinguish sides and faces can help decipher these harder prints.


 Surface identification quiz



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Interpretation of Metal Fab Drawings Copyright © 2017 by Cameren Moran is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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