Shielded Metal Arc Welding

Design Brief: To understand Shielded Metal Arc Welding (SMAW) or “stick” welding theory.

Context: Safety is first in the workshop. Read and understand all of the safety rules before using any tool or machine.

Possible Solutions: Have instructor demonstrate (mandatory) the tool first. Have another student demonstrate the tool. Read the manual that comes with the tool (mandatory). Ensure that you have been certified “competent” by the instructor before you use the tool (mandatory).

Detail Design: The following are the steps to understanding stick welding theory:

Rod Identification

Coating on a Rod

Provides a shield for the arc against contamination from oxygen and nitrogen in the air, which will enter the weld during the molten state


Slag forms after the weld is made. It protects the metal during cooling and shapes the weld. It is removed after the weld has cooled with a slag hammer and/or a wire brush.

Rod I.D. (E-7014)

E - Means Electrode (arc electric weld)

70 - Tensile strength in 1000psi (70,000psi)

1 - Welding position (all position – flat, downhand, horizontal, vertical, overhead)

4 - Refers to the power supply (AC or DC polarity); coating contains and iron powder, 30% faster metal deposit than most rods, producing low splatter and easy slag removal, and less chance of sticking.

  • Fast fill and fast freeze electrode, used where high speed is necessary
  • Easy to start
  • Very good for mild steel

Rod Size and Length

Rods vary in size for different thicknesses of metals and the amperage being used. Typical rod length is 14”     

 Electrode Diameter (inches)
 110-150 (1/4” to 3/8” plate)
 5/32  140-190
 3/16  180-260
 7/32  250-325
 1/4  300-400

Arc Welding Basics

Arc Length

Keep the tip of the rod 1/8” off the base metal (i.e., the thickness of the rod)

Angle of Electrode

Perpendicular to the metal and 20º – 30º in the direction of travel.

Striking the Arc

Two methods to strike the arc are used: scratching and tapping.

Scratching is similar to striking a large match.

Tapping is a straight up and down tapping motion

Strike the arc by moving the electrode down until it touches the base metal. When a burst of light appears, move the electrode up ¼”, hold for a few seconds, then lower the electrode to 1/8” off the base metal.

Types of Machines

There are three main types of machines used in arc welding.

  1. An AC (Alternating Current) machine has the electric current flow in one direction but then reverses direction at regular intervals. This is a transformer-type machine (often called a “buzz box”).
  2. A DC (Direct Current) machine has the current flow in one direction only. This is a rectifier-type machine.
  3. An AC/DC machine is a combination of the first two mentioned.
  • DC welders permit the widest choice of electrodes and current range and the best arc stability. It is usually used for out-of-position welding (uphand, vertical, overhead, and horizontal), sheet metal work, pipe welding, hard surfacing, stainless welding, and more.
  • AC welders have greater freedom from arc blow (a condition where the arc wanders while in corners on heavy plate or when using large rods – solution is to put ground closer to work and/or change the direction of travel), produce less splatter, and are lighter and smaller machines. They also require less electricity and require less maintenance. They are ideal for downhand welding on heavy plate using large electrodes. An AC transformer has an arc boost switch for easy arc starting.
  • An AC/DC welder offers the advantages of both.
THE ELECTRIC ARC (click image for larger size)

Materials: welder, electrodes, leathers (jacket and gloves), shielded hood.

Commissioning: Were you successful in this project when you tried it out?

Evaluation: Did this project work as you expected it to?

Reflection: Did you enjoy this project? What were you most proud of? What would you do differently next time?