A recessed tip stays cooler, which increases tip life and weld quality, when welding these rigmats using .052-in. metal cored wire with a spray transfer process.

Contact tip recess isn’t usually the first thing welders think about when they contemplate getting the best performance from their MIG welding equipment. Using the wrong contact tip recess, however, can make a quality weld difficult with even the best equipment and technique.

Incorrect contact tip recess can lead to a variety of problems, including excessive spatter, burn through and warping, insufficient penetration and porosity. Companies unfamiliar with the impact of contact tip recess might assume that encountering these problems and maintaining an extensive post-weld operation to remedy them are just inevitable parts of the welding process. Or, in extreme cases, they might even focus their troubleshooting efforts on expensive equipment upgrades. In many situations, however, there is a less expensive solution.

MIG consumables cost the same regardless of their recess, so purchasing the correct contact tip doesn’t add any cost at all to the overall operation and it can greatly reduce the amount of time spent performing functions that don’t add to the profitability or throughput of a product.

And with roughly 85 percent of a welding operation’s costs attributable to labor, any time a welder spends grinding, blasting or otherwise reworking a part translates into money that could be more wisely spent welding.

Types of contact tip recess

MIG gun consumables generally consist of three primary parts: the diffuser, the tip and the nozzle. The diffuser attaches directly to the MIG gun neck and carries the current through to the contact tip and directs the gas into the nozzle. The tip connects with the diffuser and transfers the current to the wire as it guides it through the nozzle and to the weld puddle. The nozzle attaches to the diffuser and serves to keep the shielding gas focused on the welding arc and puddle. (see graphic) Together, each component plays a vital role in overall weld quality, and needless to say, higher quality components produce higher quality welds and last longer than lower quality components.

MIG consumables are available with either fixed or adjustable contact tip recess. Adjustable contact tip recesses can be adjusted infinitely through the range of recess depths and extensions, usually by adjusting the position of the nozzle as needed or through a locking mechanism that secures the tip at a given recess. These consumables have the advantage of being able to meet the recess demands of a variety of applications and processes, but they also increase the potential for human error.

Since the key to achieving consistent results between operators lies with standardizing weld parameters, some weld engineers prefer fixed-recess tips as a way to ensure weld uniformity. Different manufacturers make consumables to accommodate a variety of contact tip recess depths, typically ranging from a 1/4-in. recess to a 1/8-in. extension.

Fixed recess tips are available in a variety of recess options. Shown here are the positions of a 1/4-in. and a 1/8-in. recess, a flush tip and an extended tip in relation to the nozzle.

The effects of contact tip recess

Tip recess affects a number of factors that can translate into differences in weld quality. The major factor that varies based on contact tip recess is wire stick out—the length of the wire between the end of the contact tip and the work surface. The greater the recess, the longer the wire stick out.

Electrically speaking, as the wire stick out increases, the voltage increases and amperage decreases. Increased voltage and decreased current tends to destabilize the arc, and can cause excessive spatter, arc wander, poor heat control on thin metals and slower travel speeds.

Another variable affected by contact tip recess is radiant heat from the welding arc. Heat increases electrical resistance, which in turn reduces the contact tip’s ability to pass current along to the wire. Poor conductivity can cause insufficient penetration, spatter and other problems that could result in an unacceptable weld.

Excessive heat also reduces the working life of the contact tip, which can increase a company’s overall consumables costs and the time operators spend changing tips. Because labor is almost always the highest cost in a manufacturing operation, any time an employee spends doing something other than their core duties—changing tips, grinding, applying spatter guard, etc.—adds up to unnecessary increases in production costs.

Shielding gas coverage can also be affected by contact tip recess. Because flush and extended tips position the nozzle farther away from the arc and weld puddle (given the same wire stick out), they are more susceptible to breezes that can blow away the shielding gas. Poor shielding gas can lead to porosity, spatter and insufficient penetration.

Which recess for which application

Always be sure to check the manufacturers recommendations when determining what contact tip recess is right for an application. Under most conditions, the general rule is that as current increases, so should recess. For spray transfer, pulse welding and other applications over 200 amps, an 1/8-in. or 1/4-in. contact tip recess is recommended. Short circuit transfer and low current pulse welding should be used with a flush contact tip. Extended tips are usually reserved for a very limited number of short circuit applications with difficult to access joint configurations, such as deep and narrow V-Groove joints in pipe welding.

The importance of tip recess is often overlooked as a source of weld quality.

Because the shorter the wire sticks out, the more stable the arc and the better the low voltage penetration, the best wire stick out length is typically the shortest one recommended for the application. For short circuit and other relatively low current applications, a flush contact tip with a wire stick out of roughly 1/4-in. is generally recommended. The stable arc provided by relatively short stick out length allows short circuit transfer to weld thin materials without risking burn through or warping and with less spatter. (Note: check wire manufacturers recommendations)

For higher current applications, however, such as those joining thick metals, using large diameter wire or using metal cored wire with a spray transfer process, a recessed contact tip is recommended to keep the contact tip away from the increased heat of the arc. A longer wire stick out for these processes also reduces the occurrence of burn back and spatter, thereby extending contact tip life. (see graphic)

Recess/Extension	Amperage	Wire Stick Out	Process	Notes
1/4-in. Recess	>200 amps	1/2 – 3/4-in.	Spray, High Current Pulse	Metal Cored wire, spray transfer, argon-rich mixed gas
1/8-in. Recess	>200 amps	1/2 – 3/4-in.	Spray, High Current Pulse	Metal Cored wire, spray transfer, argon-rich mixed gas
Flush	<200 amps	1/4 – 1/2-in.	Short Circuit, Low Current Pulse	Low argon concentrations or 100 percent CO2
1/8-in. Extension	<200 amps	1/4-in.	Short Circuit, Low Current Pulse	Difficult to access joints

A Final Thought

Often mistaken as an insignificant variable in MIG welding, contact tip recess should be one of the first places a company looks when troubleshooting excessive spatter, burn through, warping or insufficient penetration. If contact tip recess is the source of those problems, buying the right tips won’t cost any more than buying the wrong tips and will actually save money over the life of the consumables. Moreover, getting the right contact tip recess for your application can help provide higher quality welds and minimize rework. Using the right contact tip recess for the application can also result in significant savings in labor costs through reduced time spent changing contact tips, grinding spatter, applying spatter guard, and other unessential functions.