Skip Weld Symbol – How To Read And Apply Intermittent Weld Callouts
A skip weld symbol, technically known as an intermittent weld symbol, tells a welder to place short segments of weld at specific intervals rather than one continuous bead. It is identified by a fillet weld triangle followed by two numbers (e.g., 2-5), where the first number is the length of each weld and the second is the pitch, or center-to-center distance.
Using these symbols correctly prevents metal distortion, saves on consumables, and reduces project time by focusing strength only where it is required for the joint design.
Walking into a shop and looking at a fresh set of blueprints can feel like trying to read a foreign language. If you are a DIYer or a hobbyist welder, you might be comfortable laying down a bead, but those technical markings on the page can be intimidating. One of the most common markings you will run into is the skip weld symbol, which is vital for structural integrity and aesthetics.
When you first encounter a skip weld symbol on a drawing, it is usually because the designer wants to manage heat or save weight. If you weld a long seam entirely from end to end, the heat can pull the metal out of square, leaving you with a warped project that doesn’t fit together. Learning to “skip” correctly keeps your work flat, professional, and strong enough for the task at hand.
In this guide, I am going to walk you through exactly how to decode these symbols, the math behind the layout, and the shop tricks I use to make sure my marks are accurate every time. Whether you are building a custom trailer or a simple workbench, mastering the intermittent weld will elevate your metalworking game to a professional level.
Understanding the skip weld symbol on Shop Drawings
The skip weld symbol is part of the standard AWS (American Welding Society) system of weld callouts. It consists of a reference line, an arrow pointing to the joint, and specific numbers placed to the right of the weld type symbol. Usually, you will see the triangle symbol for a fillet weld, which represents the most common type of joint used in skip welding.
The layout follows a very specific order: the length of the weld segment comes first, followed by a hyphen, and then the pitch distance. For example, if you see “3-10,” it does not mean you weld for three inches and then stop for ten inches. It means each segment is three inches long, and the distance from the center of one segment to the center of the next is ten inches.
Understanding this distinction is the most important part of the process. If you mistake the pitch for the gap between welds, your weld spacing will be much wider than intended. This can lead to a joint that is significantly weaker than the engineer or designer planned, which is a major safety concern in structural projects.
Breaking Down the Reference Line
The reference line is the horizontal line that carries all the information. If the skip weld symbol is placed below the line, you weld on the “arrow side” of the joint. If it is placed above the line, you weld on the “other side.”
In many DIY projects, you will see symbols on both sides of the line. This indicates that the skip welds need to happen on both sides of the plate or T-joint. Knowing which side to start on ensures that you don’t accidentally put all your structural support on the wrong face of the metal.
The Role of the Fillet Symbol
The little triangle you see is the fillet weld symbol. It tells you the cross-sectional shape of the weld you are about to lay down. When combined with the length and pitch numbers, it creates the full instruction for your intermittent bead.
Always check the size of the fillet, which is usually written to the left of the triangle. This tells you how thick the weld “leg” should be. Combining the correct size with the correct skip pattern is the secret to a high-quality, professional weldment.
The Math Behind Length and Pitch
To apply a skip weld symbol correctly, you have to do a little bit of shop math. Don’t worry; it’s mostly basic addition and subtraction, but getting it right is crucial for a symmetrical layout. The two numbers you need to focus on are the length and the pitch.
The length is the actual distance you will be pulling the trigger or moving your rod. If the symbol says 2-6, you are making two-inch beads. The pitch is the center-to-center distance, which in this case is six inches. To find the actual “gap” or space between the ends of your welds, you subtract the length from the pitch.
Using our 2-6 example: 6 inches (pitch) minus 2 inches (length) equals a 4-inch gap. This means you will have a 2-inch weld, a 4-inch empty space, and then another 2-inch weld. Always double-check this math before you start marking your metal with soapstone.
Why Center-to-Center Matters
Using center-to-center measurements instead of “gap” measurements is a standard in the industry because it makes the layout more consistent across long spans. It allows the welder to use a tape measure more effectively without compounding small errors over a twenty-foot beam.
If you were to measure just the gaps, a 1/16th inch error on every gap would eventually lead to a weld being inches off-target by the end of the piece. By sticking to the pitch defined by the skip weld symbol, you ensure the structural load is distributed exactly as intended.
Calculating the Number of Welds
Sometimes you need to know how many segments will fit on a specific piece of steel. To do this, take the total length of the joint and divide it by the pitch. This gives you a rough idea of how many “cycles” of the skip weld you will perform.
Keep in mind that you almost always want a weld at the very beginning and the very end of the joint for strength. You may need to adjust the spacing slightly if the math doesn’t work out perfectly, but always stay as close to the specified pitch as possible.
Chain vs. Staggered Intermittent Welds
When you are working on a T-joint where both sides need welding, the skip weld symbol will tell you how to orient the beads relative to each other. There are two main patterns: chain and staggered. Each has its own specific look and structural purpose.
A chain intermittent weld means the segments on one side of the joint line up perfectly with the segments on the other side. If you looked through the metal, the welds would be stacked on top of each other. This is common for heavy structural beams where maximum rigidity is needed in specific zones.
A staggered intermittent weld is different. In this pattern, the welds on the “other side” are offset so they fall in the gaps of the “arrow side” welds. The symbol for this will show the triangles on the top and bottom of the reference line shifted away from each other rather than being stacked.
When to Use Chain Welds
Chain welds are great for projects where you need symmetrical stiffness. They are often easier to layout because you can mark both sides of the plate at the exact same time. Use these when the blueprint specifically shows the symbols aligned on the reference line.
However, chain welds can sometimes concentrate heat in one spot, which might lead to more localized warping if you aren’t careful. I usually recommend tacking the entire length of the chain before laying down the full segments to keep everything pinned in place.
The Benefits of Staggered Welds
Staggered welds are excellent for preventing distortion. Because you are alternating the heat input from one side of the plate to the other, the stresses tend to cancel each other out. This results in a much straighter finished product.
Staggered patterns are also visually appealing and provide a very consistent “hold” across the entire length of the material. If you are building something like a utility trailer frame, staggered skip welds are often the preferred method for attaching cross-members or long fenders.
Why Skip Welding is a Game Changer for DIYers
Many beginners think that more weld is always better. They want to weld every inch of every seam. While that might feel “safer,” it is often unnecessary and can actually ruin your project. Learning to follow the skip weld symbol saves you time, money, and a lot of frustration.
The biggest enemy in the welding shop is heat distortion. When metal gets hot, it expands; as it cools, it contracts. A continuous bead puts a massive amount of heat into the joint, which can cause a flat plate to curl up like a potato chip. Skip welding limits that heat input significantly.
By only welding where it is required, you keep the base metal much cooler. This means your gates stay square, your table tops stay flat, and your hinges don’t bind up. It is the hallmark of an experienced fabricator who understands how metal behaves under the torch.
- Reduced Material Cost: You use less wire, less gas, and fewer electrodes.
- Faster Cleanup: Fewer inches of weld mean less time spent with a flap disc or grinder removing spatter.
- Better Aesthetics: Clean, spaced-out welds often look more professional than a long, shaky bead that wandered off-track.
Step-by-Step: How to Layout Skip Welds
Once you’ve read the skip weld symbol and done the math, it’s time to mark the metal. Don’t try to “eye-ball” it. Precision in the layout phase makes the actual welding phase much smoother and ensures you meet the design requirements.
- Clean the Surface: Use a wire brush or grinder to remove mill scale and rust. Marks show up better on clean steel.
- Mark the Start and End: Always place a weld at the very start and very end of the joint. Mark these first using soapstone or a silver streak pencil.
- Measure the Pitch: Hook your tape measure at the center of your first intended weld. Mark every interval based on the pitch (the second number in the symbol).
- Mark the Length: Go back to each pitch mark and measure out half of the weld length in both directions. This centers your weld on the pitch mark.
- Highlight the “Weld Zones”: I like to draw a quick “X” or a squiggle in the areas where the bead goes. This prevents me from accidentally welding in the gaps when I have my hood down.
If you are doing a staggered pattern, repeat the process on the other side, but offset your first mark by half of the pitch distance. This ensures your beads land perfectly in the center of the gaps on the opposite side. Pro Tip: If you have a lot of identical pieces to weld, cut a “spacer block” out of a scrap piece of wood or metal that matches your gap distance. You can slide the block along the joint to quickly mark your start and stop points without pulling the tape measure every time.
Common Pitfalls and Safety Tips
Even with a clear skip weld symbol, things can go wrong if you aren’t paying attention. One common mistake is “cratering” at the end of each segment. Because you are starting and stopping frequently, you have more opportunities to leave a weak point at the end of your bead.
Always pause for a split second at the end of your weld segment to fill the crater before breaking the arc. This prevents “crater cracks,” which can spread and cause the entire weld to fail under stress. It’s a small habit that makes a huge difference in structural integrity.
Another issue is heat buildup over time. Even though you are skipping, if you move from one segment to the next too quickly, the heat can still accumulate. If you notice the metal starting to glow a deep red or the beads getting excessively wide, stop and let the piece cool down.
Safety First in the Shop
Since skip welding involves a lot of starts and stops, your auto-darkening helmet is your best friend. Ensure the sensors are clean and the delay is set correctly so you don’t “flash” yourself between segments. Constant arc strikes can be hard on the eyes if your gear isn’t dialed in.
Always wear your leather welding gloves and protective sleeves. Because you are moving around the piece more than you would with a single long bead, you are more likely to accidentally touch a recently welded (and very hot) segment. Stay mindful of your surroundings.
Checking for Penetration
Because skip welds are shorter, you need to ensure you are getting good penetration right from the start of the arc. If your machine is set too “cold,” the beginning of each segment might just be sitting on top of the metal rather than fusing into it. Run a few test beads on scrap of the same thickness to dial in your voltage and wire speed.
Frequently Asked Questions About the skip weld symbol
What does a 2-4 skip weld mean?
A 2-4 callout means you should make a weld that is 2 inches long, with a center-to-center distance (pitch) of 4 inches. This results in a 2-inch weld followed by a 2-inch gap.
Can I skip weld with a MIG welder?
Absolutely. MIG welding is actually one of the best processes for skip welding because the starts and stops are very clean and fast. It is much easier to manage than Stick welding, where you have to worry about slag inclusion at every restart.
Is skip welding as strong as a continuous weld?
While a continuous weld is technically stronger in terms of total load capacity, a skip weld is often more than sufficient for the design. If a skip weld symbol is provided, it means the engineer has calculated that the intermittent beads are strong enough for the intended use while providing benefits like weight reduction and distortion control.
What if there is no pitch number, only a length?
If you only see one number, it usually isn’t a skip weld. It might be a instruction for a single “tack” or a specific length of weld at a certain location. A true intermittent weld symbol almost always requires two numbers separated by a hyphen.
How do I handle the ends of a joint?
Standard practice is to place a weld at the very ends of the joint, regardless of where the pitch marks fall. These “end welds” provide extra security against peeling or shearing forces that usually start at the edges of a workpiece.
Final Thoughts on Mastering the Skip Weld
Learning to interpret the skip weld symbol is a major milestone for any DIY metalworker. It moves you away from “guessing” and into the realm of intentional fabrication. By following the length and pitch requirements, you ensure your projects are built to professional standards.
Remember that the goal of welding isn’t just to stick two pieces of metal together; it is to do so while maintaining the geometry and integrity of the material. Skip welding is your best tool for fighting warp and keeping your workshop projects looking like they came out of a high-end fabrication shop.
Next time you are at the welding table, take those extra few minutes to layout your marks with a tape measure and soapstone. Your finished project will be straighter, cleaner, and you’ll have the satisfaction of knowing you did the job right. Now, grab your welding hood, fire up the machine, and start practicing those intermittent beads!
