Here’s something they don’t tell you in welding school: there’s no official AWS symbol for tack welds. I know, right? After decades of standardizing everything from fillet welds to spot welds, the American Welding Society just… left tack welds in this weird gray area. It’s like having a dictionary that defines every word except the ones you use most often.

But here’s the thing. We still need to communicate these temporary welds on drawings. Engineers still need to tell welders where to place them. And fabricators still need to understand what’s required before the real welding begins. So what do we do?

We improvise. And over time, certain improvised methods have become industry standards, even if they’re not officially standardized. Think of it like how everyone knows what you mean when you say “Xerox” even though it’s technically a brand name.

Let me walk you through everything you need to know about tack weld symbols, from the basics to the nuances that separate good fabrication drawings from confusing ones.

What Exactly Is a Tack Weld Anyway?

Before we dive into symbols, let’s make sure we’re all talking about the same thing. A tack weld is essentially a short, temporary weld, typically under half an inch in length, that holds parts in their proper position before you lay down the real welds. Think of them as the basting stitches in sewing. They’re not the final seam, they just keep everything from shifting while you work.

The beauty of tack welds is their simplicity. You don’t need full penetration. You don’t need perfect beads. You just need enough fusion to keep parts aligned while you work. A good tack weld does its job and gets incorporated into the final weld. A great tack weld is so small and well-placed that you forget it was ever there.

Now, here’s where it gets interesting. Sometimes tack welds stay temporary. You grind them off after assembly. Sometimes they become part of the permanent joint, getting consumed by the final weld pass. And sometimes, in non-critical applications, they ARE the final weld. This ambiguity is exactly why we need clear symbols.

The Honest Truth About AWS Standards

The AWS A2.4 Standard Symbols for Welding, Brazing, and Nondestructive Examination is the bible for weld symbols. It’s hundreds of pages of meticulously detailed diagrams showing you how to indicate every conceivable welding operation. Except tack welds.

Why? Probably because tack welds were historically seen as part of the welding process itself, not a separate operation requiring documentation. They were considered common practice, something every welder just knew to do. But as fabrication became more complex and quality control more stringent, the need for clearer communication became obvious.

So we’ve developed workarounds. These aren’t random, they’re based on logical extensions of existing AWS symbology. And if you follow these conventions, any competent fabricator or inspector will understand exactly what you mean.

Method 1: The Modified Fillet Symbol Approach

This is probably the most common method you’ll see in the field. Here’s how it works.

You start with a standard fillet weld symbol, that familiar right triangle that sits on your reference line. But instead of specifying a full weld, you indicate a very small size and length. Something like 1/8 inch size with a 1/8 inch length. That tiny specification immediately signals that this isn’t a structural weld, it’s a tack.

Then comes the crucial part: in the tail of the weld symbol (that forked section at the end of the reference line), you write “TACK” in clear letters. This removes all ambiguity. Anyone reading the drawing knows this is a temporary positioning weld, not a undersized structural weld that someone messed up specifying.

The arrow points to the joint location, just like any other weld symbol. If the fillet triangle is below the reference line, it’s on the arrow side of the joint. Above the line? Other side. Need tacks on both sides? Put triangles above and below.

This method has several advantages. It uses familiar symbology that everyone already understands. It provides specific size guidance for the welder. And it clearly differentiates tacks from structural welds through both size and notation.

Method 2: The Simplified Leader Line Approach

Sometimes you don’t need all that detail. Sometimes you just need to tell the welder “put some tacks here.” That’s where the simplified approach comes in handy.

Draw a leader line (a simple arrow) pointing to the joint location. At the end of that line, write “TACK” or “TACK WELD.” That’s it. Clean, simple, unambiguous. The welder uses their judgment for exact size and spacing based on the materials and joint configuration.

This approach works great for experienced fabrication shops where the welders know what they’re doing. It’s less prescriptive, which means faster drawing preparation and more flexibility in execution. But it requires trust in your fabricators’ skill and judgment.

You might see variations like “TACK AS REQUIRED” or “TACK FOR FIT-UP.” These phrases give the welder complete discretion while still documenting that tacking is expected and necessary.

Method 3: When Details Matter (The Detailed Specification)

For critical assemblies or when working with specific material requirements, you might need more information in your tack weld callout. This is where you start adding process specifications.

Your symbol might include:

• Size: 1/8 inch
• Length: 1/8 inch
• Spacing: Every 6 inches
• Process: GMAW (Gas Metal Arc Welding)
• Filler material: ER70S-6

Why specify all this? Because tack welds, even temporary ones, can affect material properties. On certain alloys or heat-treated materials, you need to control the filler metal composition. The welding process matters too. GMAW gives you different heat input than SMAW (Stick welding), which can matter on thin materials or heat-sensitive alloys.

I’ve seen specifications get even more detailed, calling out amperage ranges, travel speeds, and post-tack inspection requirements. It seems excessive until you’re working on aerospace components or pressure vessels where every weld, even temporary ones, needs documentation.

The Tail Note: Your Secret Weapon

That tail section on the weld symbol isn’t just decorative. It’s where you communicate everything the standard symbols can’t capture. And for tack welds, it’s absolutely essential.

At minimum, write “TACK” in the tail. But you can add so much more:

• “TACK – REMOVE BEFORE FINAL WELD”
• “TACK – GMAW ONLY”
• “TACK – SAME FILLER AS FINAL WELD”
• “TACK – INSPECT BEFORE PROCEEDING”

These notes transform a vague instruction into clear, actionable guidance. They prevent mistakes, reduce rework, and ensure everyone’s on the same page.

Think of the tail note as the comment section in code. It’s where you explain the why, not just the what. A welder who understands why you want specific tack placement or removal will execute better than one who’s just following blind instructions.

Common Questions (And Answers Nobody Wants to Give)

Real-World Application (Where Theory Meets Practice)

Let’s say you’re fabricating a structural steel frame. You’ve got 1/4 inch plate that needs to be assembled in a specific configuration before final welding. Your drawing should show:

• Reference line with arrow pointing to each joint requiring tacking
• Small fillet triangle (below line for arrow side)
• Size notation: 1/8 inch
• Length notation: 1/8 inch
• Tail note: “TACK – EVERY 6 IN – GMAW”

This tells the fabricator everything they need to know. Tack size, frequency, and process. No guesswork, no phone calls to engineering, no delays.

Now contrast this with a drawing that just says “tack as needed.” On simple assemblies with experienced welders, that might work fine. But on complex assemblies or with less experienced staff, you’re inviting problems.

The Material Factor (Because Steel Isn’t Just Steel)

Here’s something people forget: not all materials tack the same way. Mild steel? Forgiving. Tack it however you want with whatever process. Stainless steel? More finicky. You need to watch your heat input to prevent carbide precipitation. Aluminum? Even trickier. You need cleanliness and proper filler selection.

This is where specifying your tack parameters matters. On a mild steel fabrication, generic tack symbols work fine. On a stainless pressure vessel or aluminum aerospace component, you need detailed specifications.

When we supply welding wire at Intiroda, we always remind customers that the same quality standards for final welds apply to tacks on critical materials. Using the wrong filler for a tack weld can compromise the entire joint, even if your final weld is perfect. It’s like using cheap primer before expensive paint – the foundation matters.

Quality Control and Inspection

Should tack welds be inspected? Depends who you ask. On non-critical fabrications, probably not. On pressure vessels, nuclear components, or aerospace parts? Absolutely.

Some specifications require visual inspection of all tacks before final welding proceeds. Others require NDT (non-destructive testing) if tacks will remain in place. Your drawing should indicate inspection requirements clearly.

Common inspection criteria include:

• Adequate fusion to base metal
• No cracks or porosity
• Proper size and placement
• Compatible with final weld process
• Free of spatter and contamination

If tacks fail inspection, they need to be removed and redone. This is expensive and time-consuming, which is why getting the symbol and specification right the first time matters so much.

Drawing Standards Across Industries

Different industries have developed their own conventions for tack welds. Structural steel fabricators might use simplified notation. Aerospace manufacturers require detailed specifications. Shipbuilders have their own standards developed over decades.

If you’re preparing drawings for a specific industry, look at their standard practices. The American Institute of Steel Construction has guidance for structural applications. The American Society of Mechanical Engineers covers pressure vessels. Military specifications (MIL-STDs) detail defense applications.

The goal isn’t to memorize every standard. It’s to understand the principles so you can adapt your symbology to the application and audience.

Practical Tips for Drawing Preparation

When you’re adding tack weld symbols to your drawings, keep these principles in mind:

Be consistent. If you use modified fillet symbols with tail notes on one drawing, use the same approach throughout the set. Don’t mix methods unless there’s a specific reason.

Be specific when it matters. Critical assemblies need detailed specifications. Simple structures can use simplified notation.

Be clear about removal. If tacks need to be ground out before final welding, say so explicitly. Don’t assume welders will know.

Consider the audience. Drawings for an experienced fabrication shop can use shorthand. Drawings going to multiple contractors need more detail.

Reference your standards. Add a general note referencing AWS A2.4 or other applicable standards. This provides context for your symbols.

The Future of Tack Weld Specification

Will AWS ever create an official tack weld symbol? Maybe. There’s been discussion in industry committees about standardizing the practice. Until then, we work with the conventions that have developed organically.

The trend is toward more specification, not less. As quality requirements tighten and traceability becomes more important, expect to see more detailed tack weld callouts. Digital fabrication and automated welding systems need precise instructions. They can’t exercise judgment the way skilled welders can.

Wrapping Up (Because Every Joint Starts Somewhere)

Tack welds might seem like a minor detail in the grand scheme of fabrication. They’re small, often temporary, and usually taken for granted. But proper specification through clear symbols makes the difference between smooth production and constant confusion.

Use modified fillet symbols with tail notes for detailed work. Use simple leader lines when appropriate. Always consider your materials, application, and audience. And remember that even temporary welds need the right materials and proper execution.

Whether you’re an engineer preparing drawings, a fabricator reading them, or a welder executing them, clear communication about tack welds prevents problems before they start. It’s not about following arbitrary rules. It’s about making sure everyone understands what’s required.

And when you’re selecting materials for those tacks, whether temporary or permanent, remember that quality matters from the first tack to the final pass. The right welding wire, matched to your application and properly specified, makes every joint stronger and every fabrication more reliable.

Now you know more about tack weld symbols than most people learn in their entire careers. Use this knowledge wisely, document clearly, and may all your tacks hold true until the final weld is complete.