Tacking it up...Tack Welding Basics

One of the first skills learned in welding that is as much of an art as it is a precise science is tack welding.  Tack welding requires a degree of practice, and an understanding of proper fitup and the character of the metal as to how it likes to draw and move as heat is applied.  While there are many types of tack welds, ranging from the small spot weld that is used for putting auto body panels together to the inch long welds that are used to hold heavy plate weldments or oil field pipe in place.   To tack properly it’s important to have plenty of clamps so that the metal is held in place so that the tack weld can be applied without the metal slipping or moving out of place.   It is also important not to overuse tack welds as it becomes difficult to properly finish the part if a long weld is required and will possibly require the grinding out of the tack welds so that the weld can be laid in properly.   While many people want to make sure their weldment is secure before they start welding, too any tacks can ruin the final results.  It’s important to carefully space tack welds out evenly.  A  good way to do this is to use a  marking pin and tape measure before hand to ensure that the welds are properly spaced.  This will ensure a quality result.  Often though when something is tacked without alternating the tack positions and just tacking consecutively making one tack right next to the other, the metal will draw.  You must space out the tacks on opposing sides to begin with if possible.  This means moving from one end to the other end or other side and then splitting the difference and repeating the process from end to end to keep things from drawing and pulling on one side.   Tacking takes patience and practice.  Unless there is a specified procedure given for tacking, it is something that is up to the individual to determine what is appropriate.  Practice will eventually make perfect, but be prepared to have a few failed tacks before you get it right.