How to Read Welding Blueprints

Professional welding demands that you understand specific instructions from the drafter.

Architects and drafters usually include detailed welding instructions in their blueprints to ensure that the welder knows exactly how the drafter wanted the welding carried out. Details include the type of weld, its size, the number of similar welds that must be carried out and perhaps even details about the joint in which the weld should be made. If you want to take up welding, you must learn welding symbols.

Look at the back of the welding symbol. It has either a word or an abbreviation on it (such as “SMAW”) detailing the process that you must carry out. This word or abbreviation sits between two lines that enclose into the reference line.

Go further down the symbol into the reference line. This line indicates where the general welding should take place. Sometimes, the symbol just finishes here. Other times, it branches out into multiple arrows, indicating multiple welding tasks. There are also times when a reference line has a break.

Look through your reference line for a break. A break in the reference line represents a joint preparation that must take place. The appearance of the break symbolizes the type of joint preparation you must make, such as a square groove.

Look at the endpoint of your reference line (the arrow). Look for symbols on the arrow. A symbol in the same side of the reference line as the arrow represents an arrow-side weld, meaning you must weld on the side the arrow points to. If the symbol appears above the arrow, you must weld on the opposite side. Sometimes, you might get a symbol on the arrow side and another break on top of it. This signifies that you must weld on both sides of the given object in the draft.

  • This covers the generic reading of symbols that appear in most blueprints, but you might come across others that won't look as familiar. The Delta School of Trades website has a more detailed description of welding symbols and their meanings.

Mikhail Polenin has been working with computers since 1997. His experience also expands to astrophysics, masonry, electricity and general appliance repair. He's written about various different subjects regarding astrophysics and electrical circuits for various online publications. Polenin attended the New World School of the Arts and the University of Florida.