is needed. Beginning welders tend to make them too small. One inch is the standard length of a tack weld. A tack should be as strong as the weld itself as it becomes and integral part of the finished weld.
What is a joggle joint?
See Figure 4–17. Joggle joints are used where a strong joint and flat surface is needed to join two pieces of sheet metal or light plate. There are hand tools available to put the joggle into sheet metal. They are useful whenever a finished surface concealing the weld is needed and where a butt joint would not work with thin sheet metal.
Figure 4–17Joggle weld joint preparation
What is the difference between a stringer bead and a weave bead?
In a stringer bead the path of the electrode is straight, with no appreciable side to side movement, and parallel to the axis of the weld, while a weave bead has a side-to-side motion which makes the weld bead wider (and the heat-affected zone larger) than that made with a stringer bead.
What is padding or overlaying and what is it used for?
Padding is when weld filler metal is applied to a surface to build up a plate or shaft, to make a plate thicker, or to increase the diameter of a shaft. It is used either to restore a dimension to a worn part or to apply an extra hard wear surface. See Figure 4–18A shaft, bar or pipe and 4–18B is resurfacing a plate.
Figure 4–18AResurfacing on shaft, bar or pipe axial and circumferential welds
Figure 4–18BResurfacing on a plate
What is the purpose of surfacing welds?
Surfacing, also called hard surfacing, is the application of extra hard weld metal (padding) to surfaces subject to severe wear and abrasion. The teeth, buckets, and blades of earth moving equipment are often surfaced, as are the interior chutes of rock crushers. SMAW, GTAW, FCAW, and GMAW processes can all perform surfacing given the proper electrode metal composition.
What does the term boxing mean?
Boxing is when a fillet weld is continued around a corner. Normally a fillet weld is made from one abrupt end of the joint to the other abrupt end of the joint. See Figure 4–19.
Figure 4–19Boxing weld
Welding on Thick Plates
What is a root pass weld and where is it used?
A root pass uses weld filler metal to close the root space between the weld faces. It is especially helpful in welding pipe and thick plates where only one side of the weld is accessible and no backing material is used.
What is a back weld?
A back weld is applied after a groove weld is completed. The back weld is made to insure full penetration through the material being joined. Before we apply the back weld we must grind or gouge into the bottom of the groove weld until we reach sound weld metal then we may apply the back weld to the bottom of the groove weld. See Figure 4-20.
Figure 4–20-21Back weld and backing weld
What is a backing weld?
A backing weld is applied to the bottom or root of a groove weld before the groove weld is applied. Because the root or bottom of the weld is made first it becomes a backing for the groove. The difference between a back and backing weld is the sequence of welding. Before the groove weld is completed the backing weld must be ground or gouged to sound weld. See Figure 4–20-21.
Why are weld backing plates used and what materials are used for them?
A backing plate is used to contain the large weld pool when joining two thick sections that are accessible from only one side. It takes the place of a root pass. The backing plate also shields the weld pool from atmospheric contamination coming in from the back of the weldment. Backing plates are usually tack welded to the two sections of the weld, but there are proprietary ceramic tapes and metal-glass tapes that perform the same function and do not need to be tacked into place. Copper and other materials are also used as backing plates. See Figure 4–22.
Figure 4–22Weld backing plate
What is a runoff plate or tab and why are they used?
It is a plate of the same material of the work being joined which is tack welded to the joint at the start and/or end of the groove joint. The runoff plate contains a groove like the pieces being joined. It prevents the discontinuities caused by beginning and ending the welding process. See Figure 4–23.
Figure 4–23Runoff plate or tab
How can a large weld be made when the electrode deposition is much smaller than the weld width?
By using multiple passes of parallel weld beads. See Figure 4–24.
Figure 4–24Multiple passes to join thick material
Slag Removal
Why is slag removal between weld bead applications important?
Slag must be fully removed between weld passes or the remaining slag will form inclusions within the weld metal and weaken it. Slag is usually removed with a slag hammer and wire brush angle grinders or pneumatic peening tools may also be used. Sometimes a wire wheel is used. Pipe welding, grinders and power wheels are used between each welding pass to assure a slag-free surface on which to begin the next pass.
Welding Cable Sizing
How do you determine what size welding cable is adequate for a task?
For copper cables, look up the cable size required in welding lead sizing chart based on the power
