Using the Arc Welder

The arc welder is used for welding or joining two or more pieces of metal together. The metal is heated to a molten state using electricity which creates an arc. Either AC or DC is used and a welding rod appropriate to the metals being used. The two pieces of metal are heated to a molten state and are fused together as the metals blend and a compatible welding rod is melted and used as a fill.

Controls: The controls on the arc welder in the materials processing laboratory consist of the following:

  • Amperage of the welder is adjusted for the electrode being used. Other welders allow adjustments for polarity; AC or DC or DC reverse.
  • Welding rod is selected based upon the material to be welded, the position of the weld, and the penetration into the metal that is needed. 

Operation: Welding heats metal and using a filler rod, joins two pieces of metal. Refer to the following illustrations.

  • Clean the metal that is to be welded. It should be free of dirt, impurities and flammable materials.
  • Adjust the arc welder to the correct setting for the material and rod being used; AC or DC polarity.
  • Connect the ground clamp to the work piece.
  • Select the proper welding rod for the metal being welded. Place into rod holder.
  • Strike an arc by quickly tapping the welding rod to the work piece or by quickly scratching it across the work piece.
  • Maintain the arc length equal to the diameter of the electrode.
  • Maintain an angle of 15 degrees off vertical with the welding rod.
  • Use a chipping hammer to remove slag from the completed weld.

Stock is being fed into the planer. Notice that the worker is wearing welding helmet for eye protection.

The weld is being cleaned of slag with a slag hammer which forms as the piece is welded.

Potential hazards: The following hazards exist:

  • Materials become hot during welding. Care must be used to avoid touching hot metals.
  • Sparks are created avoid contact with flammable materials.
  • Eyes may burn when looking at the arc. Use a welding helmet with shade 9 glass.
  • A sunburn-type burn is possible on exposed skin; cover arms and neck.

Safety practices: Because of those potential hazards the following safety rules must be followed:

  • Eye protection required. The ultra-violet and infra-red rays which are given off during arc welding will burn the eyes. A shade 9 must be used in the shield.
  • Eye protection must be worn when chipping flux and when cleaning with the wire brush.
  • Electrocution is a possibility with the use of electricity. Avoid standing in puddles or welding while standing on damp ground.
  • Do not touch welded metals as they are hot.
  • Leather gloves and an apron protect from sparks.
  • Wear long sleeves and closed shirt collar to protect arms neck from intense light, spatter and sparks.
  • Do not wear particularly flammable clothing such as chamois and nylon.
  • Tie back long hair.


Graham, Gregory S. (1981). Metalworking : an Introduction. Boston, Mass. : Breton Publishers. p. 315-333.

Walker, John R. (1972). Exploring Metalworking; Basic Fundamentals. South Holland, Illinois: The Goodheart-Willcox Co. p. 125-131.

Zaner, John. (9/9/01). Circular Saw. [Online].  Available: http://www.usm.maine.edu/~zanerj/252/woodprocess/CircSaw.htm.10 Sept. 2001.

ITT 252 - Materials Processing
Department of Technology
University of Southern Maine
Prepared by Joanne Gauley, 11/15/2001