The joining of metal components by a localized fusion is a technique used with a number of arc welding processes; it can be accomplished with both manual and mechanical procedures.

Early applications used the older, established processes of bare metal arc welding (with light flux-coated metal electrodes) and submerged arc welding. With these processes, welding was predominantly limited to the heavier gages and thinner plate thicknesses. In some cases to insure penetration, the welding was done through a prepared hole in the upper member of the joint; this is commonly referred to as plug welding. Although arc spot welding using the above-mentioned processes was not extensively used as a prime process, it was used for repairs and for tacking components together to hold them in relation for subsequent processing.

Later process developments of gas tungsten-arc welding, gas metal-arc welding and gas metal-arc flux-cored welding have greatly extended the application of arc spot welding. These more recent process developments allow arc spot welding of metal thicknesses of from 0.005 in. to heavy plates 3/8 in. thick. What process is best suited for a specific application depends on the material being welded as well as the metal thickness and joint description.

A major feature of arc spot welding is that only one side of the joint need be accessible. This advantage, coupled with the fact that normally no force is needed, allows the designer and engineer to conceive product designs which cannot be practically produced by any other welding process. Other advantages of arc spot welding to be considered are:

1. Lowe initial equipment cost compared to resistance spot welding equipment of sufficient capacity to process equivalent metal thicknesses.
2. Low electrical power demand.
3. Simplified fixturing requirements
4. Greater portability of equipment
5. Minimum operator skill required
6. No practical restriction in thickness ratio in welding light (upper part) to heavy metal gages
7. Shunting of welding currents is not encountered. The center-to-center weld distance is limited only by the associated heat-affected zones.
8. Consistency of results once suitable conditions have been established and are maintained.
9. Housekeeping is improved over submerged melt or stick welding, but is no better than with the "fine wire" process.