Follow these tips for stronger, safer shop welds.
Karen Jones is the machinery executive editor at Successful Farming and Agriculture.com. She joined the Successful Farming team in 2023 following a 19-year career on the communications team of an agricultural cooperative. tig machine
Having the right kind of welder in your farm shop can save time and money on repairs and fabrication. The tried-and-true stick welder, while still useful, has paved the way for MIG welders and even TIG welders. All three have their place, as you’ll read in this article, and general techniques and safety precautions are important for any type of welding.
MIG (metal inert gas) welding, also known as FCAW (flux-cored arc welding), is the popular choice for many farmers because of its ability to produce clean welds on a variety of materials.
1. Properly Clean and Prepare Welding Surface
The number one failure of a MIG weld is porosity, and the most common cause of porosity is welding a dirty, oily, or painted surface. Contaminants become trapped in the weld, resulting in sponge-like holes. Other causes include inadequate shielding gas coverage or improper wire stickout.
“Farmers commonly fail to adequately prepare metal before welding,” says Miller Electric’s John Leisner. “This includes removing paint, rust, dirt, and other surface contaminants, and it also means grinding out cracks.”
Hydrogen is the worst weld-destroying impurity and is a particular challenge for welders because it’s found everywhere (think water, dirt, rust, paint, manure, grease). Careful cleaning can help mitigate hydrogen’s presence in your weld, giving you a stronger and more attractive finished project.
A welding arc requires a smooth flow of electricity through a circuit, and while electrical current flows through any available path, the majority will seek the path of least resistance. If your ground is not placed near the arc, the current may find another path, resulting in poor welder performance. Firmly attach the clamp to bare metal as near as possible to the arc.
If you’ve ever fired up your MIG welder and heard popping or crackling sounds, this could be due to a poor ground clamp, according to Jody Collier, welding educator at weldingtipsandtricks.com. Copper ground clamps are best, especially ones with strong springs. A good clamp makes for a good ground.
3. Pay Attention to Wire Stickout
Wire stickout is sometimes misunderstood. According to the American Welding Society (AWS), it refers to the distance from the end of the nozzle to where the wire melts off. As a general rule, the wire should stick out from the end of the gun’s contact tip between ¼ and 3/8 inch. Too much stickout softens the arc, making the weld pile up; however, in certain situations, such as welding thin sheet metal, a longer stickout is useful.
4. Match Your Technique to Your Metal
“Use both hands when possible,” Collier says. “Rest the crook of the gun neck in one hand and hold the part with the trigger in the other hand.” He recommends heat-resistant, heavy welding gloves for protection.
The most common method is to push the gun toward the direction of the weld, known as the forehand method. Forehand welding produces shallow penetration with a flat, wide, smooth surface. The backhand method – pulling the gun toward you – produces a deep-penetration weld that is narrow and high in the center. The best method to use is determined by the thickness of your metal and how deeply the weld needs to penetrate.
When making out-of-position welds (vertically, horizontally, or overhead), use the smallest possible wire diameter size and keep the weld pool small.
Take a look at your finished welding bead. A convex shape or rope-like bead often indicates your setting is too cold for the thickness of the repair and there isn’t enough heat being produced to penetrate the base metal. A concave shape bead can indicate too-high voltage, too-slow wire feed speed, or too-fast travel speed.
5. Keep Equipment Clean and Check Settings
Make sure to match drive rolls, gun cable liners, and contact tips to the wire size you’re using. Trying to run .030-diameter wire through .035 rolls will have you constantly changing feed speed and never getting the setting right, as the grooves on the rolls are too large. The same goes for the gun cable liner and contact tip sizes.
Clean the gun liner and drive rolls occasionally, and keep the gun nozzle clear of spatter. Replace the contact tip regularly, because worn tips can lead to an erratic arc, Collier says. If a tip enters the molten weld pool, replace it immediately.
Over time, gun liners can become clogged with dust and copper from the wire. You can check the liner for feeding issues by turning off the machine, undoing the spring clamp tensioner on the rollers, and laying the gun lead on the floor, with the contact tip removed. You should be able to push the wire through without having to force it; if not, replace it. New liners are inexpensive and make a noticeable difference.
Your welder should produce a steady buzz while welding. Hissing can indicate your voltage setting is too high, says Miller Electric’s Leisner. A loud, raspy sound can indicate the voltage is too low, while a constantly changing pitch or volume can indicate too long of a wire stickout.
A good auto-darkening helmet can make a huge difference in your final output. Moving even ¼ inch off the welding track when you nod your helmet down can screw things up. With a quality auto-darkening helmet, you can see where your wire is pointing before you pull the trigger. Leather footwear along with flame-resistant clothing without cuffs or open collars are recommended to prevent burns, or places where sparks can hide and smolder.
If you must use an extension cord, use the shortest length and biggest diameter possible.
Ensure your welding equipment is on a flat surface away from flammable materials, including paper, cloth, rags, oil, and gasoline. Avoid working in damp or wet conditions. Keep the work area free from clutter and keep necessary tools nearby. Never pick up hot metal with your hands, even when wearing gloves – use pliers.
Make sure your shop area is well ventilated to protect you from fumes, dust, and particles created during welding. You can use a fan to help pull fumes away from your breathing area.
For MIG welding, an economic and efficient choice of gas is 100% carbon dioxide (CO2). However, when welding thin metal, CO2 may be too hot. Welding educator Collier suggests a mixture of 75% argon and 25% CO2 instead.
There are other shielding gas mixtures, and for certain uses it may make sense to invest in something more expensive:
For most farm shop needs, on-hand gas supplies should include CO2 and an argon-CO2 mixture.
Although the most common welding wire diameters are .035 and .045 inch, a smaller- diameter wire can make it easier to create a good weld. Try an .025-inch wire diameter when welding material of ⅛ inch or less. A smaller-diameter wire produces more stable welds at a lower current, which has less tendency to burn through.
While a lower current and smaller wire can mean greater success on thinner materials, be careful using that approach on materials 3/16 inch or thicker because a .025-inch wire may cause lack of fusion.
More ag equipment is incorporating aluminum, forcing the issue of needing to make repairs to the metal. Any wire welder can handle aluminum, and the process is fairly easy to learn, according to Lincoln Electric. Keep in mind these aluminum welding tips:
The popularity of wire welders has relegated many stick welders to the shop corner to collect dust, but these machines still have a place on the farm.
The modern stick welder can utilize both alternating current (AC) and direct current (DC), providing advantages such as easier starts, less sticking, less spatter, more attractive welds, and easier vertical and overhead welding.
Stick welding also produces deeper welds; excels in outdoor operations, where wind can blow away MIG shielding gas; works well on thick metals; and burns through rust, dirt, and paint. These welders are also portable and simple to operate.
Once only dreamed about by farmers wanting a better way to weld thin metal, aluminum, and stainless steel, TIG (tungsten inert gas) welders are becoming more common in farm shops.
TIG requires three-way coordination using both hands (one holding the heat source in a tungsten electrode and the other hand feeding fill rod into the arc) and a foot (operating a pedal or torch-mounted amperage control for starting, adjusting, and stopping the flow of current).
Miller Electric offers these tips for TIG welding success:
Even novice welders can experience some success, but a few hard-and-fast rules can produce lasting welding repairs.
Gravity is your enemy when working out of position, so counteract its efforts (particularly when wire welding) by using a little less voltage and a lower wire-feed speed to create a smaller puddle. Reversing polarity to concentrate the heat at the electrode tip results in cooler welding, which lets the weld puddle cool faster to prevent dripping. Here are tips on welding out of position:
Welds can crack for one or more of the following reasons:
Rigid parts are more prone to cracking. If possible, weld toward the unrestrained end of such parts and leave a 1/32-inch gap between plates for free shrinkage movement as the weld cools. Peen each bead while it is still hot to relieve stress.
Sponge-like holes or tiny bubbles that appear on the surface of a weld are sure signs that your weld suffers from porosity, welding educator Collier says.
Weld porosity can take many forms, including surface pores, wormholes, crater pipes, and cavities that are seen (on the surface) and unseen (deep in a weld).
Beyond its ugly appearance, porosity predicts a poor, weak weld.
Possible causes of porosity include:
Keep the puddle molten for a longer time to allow gases to boil out of the weld before it freezes.
If you must weld in a location where you can’t prep the surface well, or on a high stress point, reinforcing your weld is important. Reinforcement is also needed if a piece has broken more than once in or near the same place as a previous repair.
Be sure to bevel edges at a 30° angle where the new metal meets the old metal. Doing so provides better welding penetration.
For heavier sections of material, leave a small space at the bottom of the joint. To do this, first bevel the edges and then grind along the bottom of the bevel until it’s the thickness of a nickel.
smaw welding Material over ¼ inch thick should usually be welded in multiple passes.