tack welding

How To Tack Weld

How could anyone possibly screw up tacking? The truth is, you could be tacking wrong and never know it. This is because most of the problems with tacking incorrectly often don’t become apparent until much later in the process. As a result, tacking often goes overlooked when troubleshooting issues. But with a few simple tricks, you can rest easy knowing you’re tacking the right way. Take a look below, where we break down what tack welding is and how to do it right. 

What Is Tack Welding?

Tack welding is a welding technique used to hold parts in place temporarily.  It's called "tack" welding because of the tacks, or small welds, used along a welding joint to keep components aligned and fixed in position. These tack welds ensure that the parts don't move during the welding process, which helps maintain the accuracy and alignment of the final weld. Tack welding is commonly used in fabrication and assembly processes, particularly when working with large or complex structures.

Spot Welding vs. Tack Welding

Tack welding and spot welding are two distinct welding techniques often confused due to their similar applications in holding metal parts together. Tack welding, as we already explained, is used to temporarily hold parts in place before the final welding is performed. Spot welding, on the other hand, creates a permanent joint between two metal surfaces.

Despite these differences, tack welding and spot welding are often used interchangeably because both methods involve creating welds at specific points to hold metal parts together. However, it is essential to recognize that tack welding is a temporary solution primarily for alignment purposes, while spot welding is a permanent method used for joining metal surfaces.

Tack Weld Symbol

A weld tack symbol is a notation used in welding blueprints and drawings to show the welder where tack welds should be placed. Unlike most other welding techniques, there is no official tack welding symbol. Instead, it's common practice to use the spot welding symbol, which is a circle.

Features of a Weld Tack Symbol

  1. Symbol: The tack weld symbol usually consists of a small circle or a dash placed on the reference line of the welding symbol.
  2. Placement: The symbol is positioned at the specific points where the tack welds are required.
  3. Context: It is often accompanied by additional information such as the length of the tack welds or the spacing between them.

Using More Than You’d Think

Often, welders worry about tacking too much or making their tacks too large (potentially causing warpage). In fact, many welders have been taught that tacking shouldn’t penetrate your workpiece at all but instead hold the pieces together by resting on top like a piece of scotch tape. This leads to weak tacks, which can make the pieces shift or break apart.

If you’re using clamps and tacking in the correct spots (tips #2 and #3), you won’t have to worry about too much tacking. When tacking, you need to get enough heat to penetrate both pieces. Otherwise, fusion won’t occur, and your tack won’t stay.

Many welders think of a tack as a quick weld that can be done on the surface to hold two components in place. However, these surface welds, also called bridge tack welds, don't penetrate deep enough into pieces to truly join them together.  When you’re tacking, penetration is key (just as normal welding). This can be done by doing a circular motion (vs. welding in one single spot) or a U-shaped motion. Regardless of which approach you choose, the goal is to make sure both pieces of metal are being fused together.

Dealing with Warpage

When metal is heated, its molecules expand. Then, when it cools, they contract in a different place than where they started. This is why welding pieces at perfect 90-degree angles can be a nightmare. Every time you weld, the metal changes its composition.

In an attempt to avoid warpage, many welders will do quick tacks that don’t get a lot of penetration. This leads to a host of other problems (tip #1). There’s a better solution. First is to pay attention to where you’re tacking. While every situation is a little different, a decent guideline is to try and tack all sides of the piece equally. In a perfect world, this would mean your piece was affected equally on all sides and should, therefore, be fairly close to its original position before you started tacking. Of course, we don’t live in a perfect world, which leads us to tip #3:

Clamping and Re-Measuring

We all do it. We try to use tacks instead of clamps. While a tack might hold your pieces together like a clamp, it can’t replace a clamp’s ability to regulate warpage. Good welding clamps are designed to hold your pieces in the correct spot even when warpage occurs. Some experts will tell new welders to even think of metal as elastic. If you don’t have it strapped down while it’s being heated, it’ll going to move on you. With workpieces that require a lot of precision, it’s not uncommon to have more clamps than metal.

No matter how many clamps, tacks, or any other trick (pre-heating, etc.) you use, your pieces will often shift during tacking. If your project requires precise angles and distances, it’s vital to make sure you check your measurements after taking each side. If you notice an issue early on, you can often use a clamp, brute force, or tack the opposing side to correct the issue. If you’re not re-checking your measurements, you could end up tacking a piece not well enough. The only way to fix it is with your old friend, the grinder.

Tacking Is an Essential Part of a Welder's Toolset

Unfortunately, there’s not enough bandwidth on the internet to explain every situation you might face when it comes to where and how much you should tack. But by even paying a little more attention while tacking, you’ll find your pieces are easier to weld and don’t end up crooked or shift positions.

If you’ve needing some new clamps that are perfect for dealing with warpage, make sure you check out strong hand clamps. Click the button below to learn more, or visit our store to shop for the best welding equipment!