A stitch weld or stitch welding is intermittent welding, that is equal in length and spaced out evenly according to the specification used to join two pieces of metal together. It's just one of the many types of welds out there.
Stitch Weld Symbol:
Miller has a great article on deciphering weld symbols that you can checkout here. Below is the welding symbol for a stitch weld.
In the above image, you can see this weld requires a 1/4" bead height and width. It also requires a 2" fillet weld spaced out 4" from the start of one weld to the start of the next. Your project will dictate what these numbers are.
Unlike seam welding, it is not continuous welding. You can look at it as seam welding with breaks along the weld.
How do you make a stitch weld?
1. Prepare To Weld-
The first thing before any welding is performed is to prep your materials and adjust your welder settings for the particular metal properties. Getting the welder settings right is critical to keep the heat right and prevent unwanted distortion.
Part of any fabrication project requires two things with no glory, material preparation and clean up. Never the less, they're both important steps of the fabrication process for successful welds.
Start by cleaning your metal surfaces with a grinder until it's free of mill scale, rust and dirt on the surfaces to be welded. Wipe down with acetone or alcohol to remove any contaminants.
2. Clamp & Tack Your Workpiece Into Position-
Stitch welding, like any other weld requires positioning the metal to be welded. This can be done using clamps or magnets to hold the proper joint alignment during the welding process.
After tack welding, grind out the tack welds and run a wire wheel or flap disc along a joint and remove any welding splatter and contaminants. This step may seem overkill, but will provide a cleaner and aesthetically appealing weld.
3. Weld your joint-
Lay your first bead in the joint according to the drawing. Next, you'll move down the joint and lay the next bead and continue this process according to the procedure.
Stitch Welding vs. Seam Welding?
Stitch welding is intermittent welding where as seam welding is a continuous weld down the joint. Some applications require a continuous weld like roll cages where standard fabrication welds often just require stitch welding.
Common Stitch Welding Questions-
Is a stitch weld strong?
If the welds are completed properly, it'll be just as strong as if not stronger than the metal being welded.
When do you use a stitch weld?
The stitch weld is usually applied to areas where it is necessary to maintain the strength or to prevent heat distortion. A stitch weld includes two commonly encountered kinds: fillet welds and butt joint welds.
Auto body panels are a good place to use the stitch welding technique. You can start by tacking the joint. Then use stitch welds in super short tacks spread far apart to prevent the thin metal body panels from warping because of too much heat.
As you continue to fill in the open joints and sand it down to smooth metal, it will eventually look like a a solid seam weld.
Why do you stitch weld?
Stitch welds require less filler element and therefore reduces the amount of weight and cost of a weld. This type of weld will prevent warping by having the heat spread over the length of the weld.
Seam welding concentrates a lot of heat down the entire seam weld. This continuous bead requires more filler and cost more.
Final Thoughts on Stitch Welding-
Hopefully this post helped clarify the difference between stitch welding and seam welding. A seam weld is strong, but not always needed. It will cost more, weigh more and quite often warp the material the seam weld is being performed on.
If you don't need to weld the entire length of your next weld, try using a stitch weld.