2T vs. 4T vs. S4T in Welding

Welding is a fantastic metal joining method that allows you to adjust dozens of parameters to improve performance. You can adapt amperage, voltage, wire feed speed, pulsing, you name it.

Did you know you can also adjust the way your trigger works? Trigger adjustments are carried out through features known as 2T, 4T, or the latest S4T. Most renowned welders provide these features to make everyday welding easier.

If you are new to welding or didn't bother too much to explore trigger settings, don't worry; we've got you covered. In this article, we will explain the fundamentals and applications of 2T vs. 4T vs. S4T in welding.

YesWelder DP200 Dual Pulse MIG Welding
Source: https://www.youtube.com/watch?v=qMAUAQ-eK8k

Trigger Controls in Welding (2T/4T/S4T in Welding)

While browsing through your welder's features, you probably noticed a small button with the markings 2T/4T or S4T (present on newer welders). In the feature, the "T" stands for touches. Therefore, we have:

• 2T - Two Touches

• 4T - Four Touches

• S4T - Special Four Touches

By default, your welder is set to the 2T option. In 2T, you press the trigger, and the arc appears. The arc is present as long as you are holding the trigger. Once you release it, the arc stops.

In a nutshell, you press the trigger to start and hold it as long as you are welding. Once you release it, you end your welding. If you count, this operation gives us the total amount of 2 touches to start and finish the welding, ergo the name 2T.

The 4T stands for four touches, meaning you will need four touches to start and finish the welding. You press and release the trigger to initiate the arc (two touches) and press and re-release it to terminate the arc (two more touches). The most significant difference compared to 2T is that you don't need to hold the trigger to weld. This is particularly helpful during long runs when holding the trigger can cause hand fatigue.

However, these are just the basics of 2T/4T welding. Depending on the welding method (MIG or TIG), the number of touches can affect how the arc starts and is carried out.

Torch Button TIG Welding
Source: https://www.youtube.com/watch?v=p2X_e2bZJYU

2T/4T in TIG Welding

Many seasoned welders use a foot pedal to control the arc during TIG welding. However, using 2T/4 T mode can reduce hand fatigue and affect the quality of your welds.

Welders consider TIG (GTAW) welding to be one of the most complex welding methods. That's because welding machines allow you to set each part of the welding process, from starting amps to ramp up, peak amps, ramp down, and end amps.

In the process of reaching start to end, the 2T/4T trigger can have a crucial effect on the weld. Let's see how.

2T In TIG Welding

Like other welding methods, 2T in TIG welding is pretty straightforward and the default setting of the torch. There are no shenanigans here.

You press the trigger on your torch to start an arc, which immediately reaches the working amps. As long as you hold the trigger, the arc is present, and you are welding. Once you are at the end of the joint, you release the trigger. The arc stops, and you are done welding.

The foundations are straightforward. However, you can add a ramp-up rate to gradually increase the amperage toward the working amps or a ramp-down rate to decrease the amps gradually at the end.

As noted, 2T is the default option for TIG welding, and it is perfect for short welds on mild steel.

4T In TIG Welding

4T in TIG welding is a bit more complex. The first two and last two touches won't just turn on and off the arc; they will also affect the start and end of the arc. Here is how.

To start a weld in 4T TIG, you press and release the trigger. Once you press and hold the trigger (1st touch), the shielding gas starts, and the arc emerges at starting amps. The starting amps can be lower than the working amps to avoid rapid metal overheating.

Once you release the trigger (2nd touch), the machine begins the preset upslope cycle until it reaches total operating amperage. Gradually gaining the working amps prevents metal from quickly overheating and burning through.

When initiated by the first two touches, the arc runs at the working amperage. You don't need to hold the trigger. You can use the foot pedal to adjust the amperage as you go, but your finger is free, reducing hand fatigue during the long welds.

Once you are close to the end of the joint, you need two more touches to terminate the arc. When you press and hold the trigger (third touch), the welder turns to the ramp-down procedure. The amperage decreases to the end amps, which are lower than the operating amps, allowing you to fill the crater appropriately. A crater is a nasty defect that appears at the end of the joint if you prematurely finish the weld. Lowering the end amperage will help you deal with this issue.

Finally, you release the trigger (fourth touch) to terminate the arc. The post-flow occurs to promote the torch cooling and extend the consumable life.

4T TIG Welding Operation Modes
Source: https://www.youtube.com/watch?v=uzPrZb0oXT4

2T/4T/S4T in MIG Welding

MIG welding is a relatively straightforward method and a favorite of many beginners. Fundamental MIG welders, such as YesWelder MIG205 DS, don't have many setting options and welding parameters. However, they often feature 2T or 4T.

Nonetheless, 2T/4T in MIG welding is much more straightforward. Since ramp-up and ramp-down settings are rarely available, this feature is mainly used to reduce hand fatigue and improve welding convenience.

2T In MIG Welding

Like with TIG, 2T in MIG welding is a default, and many consider it a non-feature. Once you press the trigger, the welding wire starts at the preset wire feed speed. As long as you hold the trigger, the wire runs, and you are welding.

Once you release the MIG gun trigger, the wire stops, the arc extinguishes, and you are finished welding. As you can see, it is not rocket science. 2T in MIG welding is something you have been doing all along, but you didn't know it.

Compared to TIG welding, basic MIG welding and 2T have no ramp-up or ramp-down rates. Therefore, this is a straightforward method many beginners will use. You cannot go wrong with 2T MIG on a wide variety of metals, including mild steel, stainless steel, or aluminum.

MIG Welding Stainless Steel
Photo by @Ablessedwelder (TikTok)

4T in MIG Welding

Unlike with TIG, 4T in MIG welding is a relatively simple feature. Its primary function is to make long welding runs more convenient and reduce hand fatigue.

To operate 4T in MIG, you also need the four touches to start and end an arc. To start an arc, you press and release the trigger (2 touches). However, the essential MIG welders don't have advanced options such as start amps or ramp-up. As a result, once you release the trigger, the current immediately reaches the working amps, and you are welding.

To terminate the arc, you press and release the trigger once again (2 more touches). Since there are no ramp down or end amps, releasing the trigger will immediately terminate the arc, and the welding stops.

Therefore, welders primarily use 4T in MIG welding for long runs. Not having to hold the trigger throughout the weld joint can significantly reduce hand fatigue and help you focus on your weld puddle.

Advanced Settings in MIG Welding and S4T

MIG welding has evolved significantly in the last few years, so we are seeing significant improvements in weld control. In addition to pulsing, MIG welders such as our YesWelder DP200 Pulse and Dual Pulse MIG welder allow you to control the entire process, just like state-of-the-art TIG welders.

If you like to fine-tune your MIG welding performance, you will have to adjust the advanced settings. Advanced MIG welding settings include starting amps (% of the base amps), start slope (0-10 seconds), crater slope (ramp down 0-10 seconds), crater amps (end amps % of base amps), burn back and post flow.

As a result, you get a TIG-like control with your MIG welder. This advantage is ideal when welding heat-sensitive metals such as aluminum or stainless steel. Additionally, you can use them to fill the crater and adequately finish the welds.

MIG Welding Stainless Steel on S4T Mode (Advanced MIG)

S4T in MIG Welding

Special four-touch trigger control (S4T) is typically reserved for advanced MIG welders. Instead of just turning the arc on and off with four touches, S4T is quite similar to 4T in TIG welding.

S4T Advanced MIG Setting

To initiate the arc, you press and release the trigger. Once you press and hold the trigger (1 touch), the gas starts, and the current starts at the beginning amps. The starting amps are typically represented as a percentage of the working amps, ranging from 0% to 200%.

Anything from 1 to 100% means you are using a low-current start to reduce heat buildup and burn-through on thin metal. However, you can go over 100% to use a hot start. The hot start delivers a boost of amps at the beginning of the cycle to preheat thick or heat-sensitive pieces right before the welding.

Releasing the trigger (2nd touch) initiates a starting slope in periods of 0-10 seconds. Since MIG supports a hot or low-amp start, this is called a starting slope rather than an upslope or downslope. In a nutshell, it takes that period to turn to work amps from starting amps.

Terminating the Arc in S4T

As with TIG welding, the arc remains even though you're not holding the MIG gun trigger. To stop it, you will need two more touches, but in MIG, that's known as crater setting. The crater settings involve reducing the end amperage to allow welders to fill in the joint.

Therefore, pressing and holding the trigger (3rd touch) will commence a crater slope (0-10 seconds). You can adjust the time the arc takes to turn down from working amps into the crater amps. As long as you hold the trigger, the welder will run at crater (low) amps, allowing you to fill the end of the joint.

Once you release the trigger (4th touch), the arc stops. The welder initiates a burnback (if set), where welding wire retracts back into the welding gun, preventing it from sticking to the workpiece or a nozzle. The post-flow starts to cool down the torch and extend the consumable lifespan.

Brief Overview of 2T vs. 4T vs. S4T

Best Applications For Each Trigger Mode

If you are unsure which one to use for your specific welding applications, here are some practical recommendations.

• Use 2T for easy applications: 2T is a default mode, and you can use it for any household project and home applications. This should be your go-to trigger mod for easy and convenient mild steel welding, both TIG and MIG. If you are still learning how to weld, stick to 2T.

MIG Welding DIY Roses
Photo by @mya_simpson1 (TikTok)

• Use 4T MIG for long welds: Frequently running long MIG weld beads in 2 T can cause hand fatigue. Holding the torch button throughout the day can even cause repetitive strain injuries, so switch to 4T to rest your hand. Since basic MIG has no advanced settings, 4T is just an easy way around the welds.
• Use S4T for advanced MIG welding: S4T will provide you with a TIG-like control with your MIG welder. Use the first two touches to weld at starting amps, whether hot or low-amp start. The start slope will help you gradually reach the welding amps. Use the last two touches to reach crater amps and weld at lower amps gradually. Like TIG, S4T MIG is ideal for tricky and difficult-to-weld metals, but it requires more skill to operate.
• Use 4T TIG for best control: 4T in TIG welding allows you to control the entire welding process manually. Weld at the starting amp for the first two touches to reduce heat buildup and the risk of burn-through, gradually reaching the working amp. The last two touches reduce the amp and adequately fill the joint. In conjunction with the foot pedal, 4T is beneficial when welding heat-sensitive metals such as aluminum or stainless steel.

TIG Welding with a Foot Pedal
Source: https://www.youtube.com/watch?v=VNx9-Ho21xE&t=845s

Final Thoughts

2T/4T/S4T are trigger control modes you can use to make your everyday welding much more convenient. The "T" stands for the number of touches you need to start and end the arc, and the choice will depend on specific applications.

2T is a default mode and a best friend for most everyday DIY and hobby welders. Unless your projects require welding exotic and heat-sensitive metals, you are likely to use it even as a seasoned welder.

4T is used to reduce hand fatigue on the long runs, but it can also help you control the arc performance. Seasoned welders use it when they need to weld tricky metals with TIG or advanced MIG welding, but it takes skill to master.