Knowing which size contact tip to select is a crucial part of getting your MIG welding equipment set up correctly. Here you will find a guide on selecting a contact tip for your MIG welder.
How do I know which sized contact tip to select for my MIG welder? Manufacturers recommend that you match the size of the contact tip to the size of the wire. For example, you would choose a 0.023” contact tip for a 0.023” wire. There are certain situations where it is an advantage to either oversize or undersize a contact tip.
Those special circumstances will be discussed later in the article. We have also included a simplified chart, including the recommended applications for the common MIG welding wire sizes.
Table of Contents
What Does The Contact Tip Do?
I’m going to briefly touch base on the significance of the contact tip and the role it plays in the MIG welding process for those who are new to MIG welding.
The contact tip is located at the nozzle of the MIG welding gun. The wire is fed through the contact tip to the weld. The contact tip transfers current to the wire so that the wire can create the arc, which then melts metal pieces together.
If you are a visual learner like me, I recommend watching this video below, which explains the crucial components of the MIG welding machine.
Contact tips come in a range of sizes. Selecting the correct contact tip for the job is crucial because you want to create optimal conditions in which the wire feeds through the tip with minimal resistance.
Selecting the right contact tip is the difference-maker between laying down a quality weld the first time and having to grind off bad welds to try again.
Choose A Contact Tip That Matches The Size Of The Wire
In the majority of circumstances, choosing a contact tip that is most compatible with the size of the wire will yield the best results.
In select circumstances, choosing an undersized contact tip can improve the quality of the weld. This applies to cases in which you are using a wire fed from a drum weighing 500 pounds or more.
In the vast majority of applications, using an undersized contact tip will increase friction. In MIG Welding, increased friction leads to a lack of control over the wire feeding process.
This results in evident burnback at the tip, characterized by the formation of a weld inside the contact tip itself.
On the opposite end of the spectrum, choosing a contact tip that is oversized for the wire leads to a decrease in the amount of current transferred from the contact tip to the wire.
Choosing an oversized contact tip also leads to an increase in the temperature at the contact tip. This can also lead to burnback.Too much heat can also reduce the lifespan of the contact tip. This can run up your operating costs as you have to replace parts more often than you normally would have to.
What Is Contact Tip Recess?
On a MIG Welding Contact Tip sizing chart, you will notice a column that says “Recess/Extension.” Understanding this measurement is crucial for being able to pick out the right contact tip for your work, although it is often an overlooked factor.
The contact tip recess is a measurement of the position that the contact tip takes within the nozzle. The greater the recess value, the longer the wire sticks out at the end of the nozzle.
Adjustable Recess Vs. Fixed Recess
Contact tips are manufactured with either an adjustable recess or a fixed recess. Adjustable recess contact tips can offer advantages if you are working on a variety of projects. The downside to adjustable recess is that they leave room for error.
If you are in a situation where multiple people are using your MIG welding equipment every day, then you might want to avoid potential confusion by rolling with fixed recess contact tips rather than the adjustable ones, as is recommended in Fabricating & Welding magazine.
How Are MIG Welding Contact Tips Sized?
Looking at contact tip sizes can be like reading a foreign language if you don’t know what you should be looking for. Contact tip thread size is reported in both inches and millimeters.
MIG Welding contact tips are selecting according to:
- The size of wire that the particular tip is compatible with
- Type of Wire Being Used
- The cast of the wire
- The quality of the wire
You can learn more about why it’s important to select the right contact tip thread size in The Weldermagazine.
Size of Wire
Contact tip thread size is often expressed in terms of the size of wire that it is compatible with. If your wire is 0.030 inches in diameter, then you will want to seek out a contact tip, such as this Miller MIG Contact Tip, that is rated 0.030 inches.
Type of Wire
The American Welding Society (AWS) Code 5.18 allows some flexibility on the contact tip; you can select for a certain type of wire.
If your wire is solid, the code states that there is a +/- 0.001” tolerance range for 0.045” wire. In other words, if the wire in your machine is a 0.045” wire, then you would only be able to operate with a contact tip sized from 0.044-0.046” to be in accordance with AWS code.
There is a +/- 0.002” tolerance for tubular wires. Tubular and aluminum type wires are known to perform best with either standard or oversized contact tips. On the other hand, the solid type of wire can be paired with undersized contact tips because the rigid structure leads to fewer problems with feeding the wire through the tip.
The Cast Of The Wire
The cast of the wire also determines what size of contact tip is compatible with your MIG welding setup. The cast of the wire is basically its curvature.
This is more of a factor if you are buying your wire in bulk packages such as drums or reels. Wires in bulk packages have a larger cast value (or more straight curvature) than wires packed in spools or coils.
This means that you can more readily pairundersized contact tips with wire found in drums or reels.
The Quality of the Wire
High-quality wires give you more leeway as far as being able to choose an undersized contact tip.
Standard MIG Contact Tip Sizing Chart
Here you can see a standard chart for MIG Welding Contact Tips. This chart has been adapted from the one here. As stated earlier, manufacturers recommend matching the contact tip size to the wire size, though there are situations in which it is beneficial to either oversize or undersize the contact tip.
Those situations are discussed above. For the sake of simplification, this chart has been standardized and includes a column on the recommended usage for each wire size.
|Wire Size||Recommended Contact Tip Size (Standard Duty)||Recommended Usage|
|0.023”(0.6 mm)||0.023”(0.6 mm)||tight fit joint (less space between gap), delicate materials such as stamp steel|
|0.030”(0.8 mm)||0.030”(0.8 mm)||Railing, cap rails, small angle iron pieces|
|0.035”(0.9 mm)||0.035”(0.9 mm)||Most common size for fabrication shops|
|0.045”(1.2 mm)||0.045”(1.2 mm)||Galvanized sheet metal|
|0.052”(1.3 mm)||0.052”(1.3 mm)||Plate steels with moderate amounts of rust or mill scale|
For a more detailed look into the wire size sand corresponding contact tip sizes, you should be rolling with, be sure to look at the chart on the back of your machine or at the user manual for your machine.