The Lincoln K1170 AC225: Why This "Old" Welder Is a Stick Welding Classic

The Enduring Legacy of the “Tombstone”

If you’ve spent any time in an old garage, a farm workshop, or a high school shop class, you’ve probably seen it: a heavy, unmistakable red box, standing about waist-high, with a big crank or a tapped selector on the front.

This is the quintessential American “tombstone” or “buzzbox” welder. And for decades, the LINCOLN ELECTRIC K1170 AC225 has been the archetype of this category.

You might be looking at one for sale online, or maybe you’ve just inherited one. You’ll quickly discover it’s been discontinued. This might lead you to ask, “Is this thing obsolete?”

The short answer is no. This “old” technology is not only relevant, but it also remains one of the most reliable, rugged, and effective tools for learning the craft of stick welding. To understand why, we need to look past the modern, lightweight inverter machines and understand the simple, powerful science inside this red box.

What Exactly Is an AC Transformer Welder?

The K1170 AC225 is, at its heart, a massive and very simple piece of equipment: a step-down transformer. It does one job and does it incredibly well.

• It takes high-voltage, low-current electricity from your wall (more on that later)
• It uses the principle of electromagnetic induction (passing the power through massive copper windings)
• It “transforms” it into low-voltage, high-current electricity that can sustain a welding arc.

This design is the opposite of modern, lightweight “inverter” welders, which use complex electronics, transistors, and high-frequency switching to achieve the same goal.

The inverter is a computer. The Lincoln AC225 is a hammer. It has almost no moving parts (save for a cooling fan) and no complex circuitry to fail. This is why welders from the 1980s, like the one a customer review from 1983 mentioned, are still in service today.

Deconstructing the K1170’s “Tombstone” Specs

When you look at the product data for the K1170, you’re looking at a blueprint for a classic residential-use machine. Let’s break down what those numbers actually mean for you in the workshop.

1. The Power Source: AC 60Hz and “That” 220V Plug

This is the first and most important hurdle. This is not a standard 120V household plug-in tool.

• AC (Alternating Current): The current from the machine alternates its direction 60 times per second (60Hz). This is the standard in North America. It’s simple and effective for many common welding rods.
• The Power Draw: To generate its 225 amps of welding power, this machine needs a massive electrical supply. As one user in the product reviews correctly noted, “You will need a proper 220 plug on a 50 amp breaker.”

This is not a suggestion. This is a requirement. This welder is designed for a 220-240V, 50-amp circuit—the same kind you’d use for an electric stove or a heavy-duty air compressor. If you only have standard 120V wall outlets, you will not be able to run this welder. This is its single biggest barrier to entry for residential use, but it’s also the source of its immense power.

2. The Fire: A Versatile 40-225 Amp Range

This is the machine’s “throttle.” The amperage dial on the front directly controls the “heat” of your arc. The K1170’s range is its key to versatility.

• Low End (40-75 Amps): This is for welding thinner materials. The product description notes it’s for “metals 16-gauge & heavier.” At 40 amps, you can just manage 16-gauge (approx 1/16” or 1.5mm) steel, but as one user review warned, it “will burn through 16 or 18 gauge steel if you are not careful.” This low end is for delicate work and requires a steady hand.
• Mid-Range (75-150 Amps): This is the workhorse range. It’s perfect for welding 1/8” to 1/4” steel, which covers most DIY, farm repair, and hobbyist fabrication projects.
• High End (150-225 Amps): This is where the K1170 shows its power. At 225 amps, you can burn 3/16” or even 1/4” electrodes, allowing you to weld 3/8”, 1/2”, or even thicker steel in multiple passes.

This range is why customers say it “performs well for their needs” and can “get the job done.” It spans from light-duty repairs to heavy-duty fabrication.

3. The Materials: Steel, Stainless, and Cast Iron (And What’s Missing)

The K1170 is a Shielded Metal Arc Welding (SMAW), or “stick,” welder. The materials it can weld are determined by the electrodes (rods) you can use with it.

• Steel (Carbon & Low Alloy): This is its primary function. It will weld mild steel all day, every day. This is its “bread and butter.”
• Stainless Steel: As the product description claims, yes, you can weld stainless steel. You need to buy specific stainless steel electrodes (e.g., 308L-16) that are listed for AC use.
• Cast Iron: This is also possible, but it’s an advanced skill. It requires specialized (and expensive) nickel-based electrodes and a careful process of pre-heating and slow cooling to prevent the iron from cracking. The K1170 provides the power, but the technique is all on you.

The Big Limitation: Aluminum.
A common question, as seen in the product’s Q&A, is “Can it weld aluminum?” The answer with this machine is a definitive no. Welding aluminum with AC requires a high-frequency, stabilized arc and balance control, features found in specialized (and much more expensive) TIG welders. This machine is for ferrous metals (those containing iron).

The “Soul” of a Buzzbox: What It’s Like to Weld

There’s a reason these are nicknamed “buzzboxes.” When you strike an arc, the entire machine hums with a loud, vibrating 60Hz buzz.

The “smooth AC arc” mentioned in the description is a key feature. Because the current reverses 120 times per second (crossing “zero” each time), the arc can be prone to extinguishing. The K1170’s well-designed transformer helps maintain the arc, making it “smoother” and easier for a beginner to control than cheaper, less-refined AC welders.

However, welding with AC forces you to learn excellent technique. You must hold a very tight, consistent arc length. If you pull the rod too far away, the arc will go out.

This is why many welding instructors love these machines. A modern DC inverter welder is “easier” and more forgiving, but it can mask bad habits. The K1170 is a strict but fair teacher. If you can lay down a good bead with this machine, you can weld with anything.

The Verdict: Should You Buy a K1170 AC225 Today?

Even though it’s discontinued, the K1170 and its “tombstone” cousins are frequently available on the used market, often for a very low price. So, is it a good buy?

YES, if: * You have access to a 220V, 50-amp circuit (or can have one installed). * You primarily want to weld steel from 1/8” to 1/2” thick. * You want a machine that is virtually indestructible and has no electronics to fail. * You are on a tight budget and find one for a good price. * You want to learn the fundamental skills of stick welding.

NO, if: * You only have 120V household outlets. * You need to weld aluminum or very thin (20-gauge) sheet metal. * You need a portable machine. The K1170 is “portable” in that it has a handle, but it is very heavy (often 70-100+ lbs). It’s not something you casually move. * You are frustrated easily by a steeper learning curve.

A Final Word: The Responsibility of Power

The K1170 AC225 is a powerful tool, and with that power comes a non-negotiable responsibility. The process of arc welding is fundamentally dangerous if disrespected.

• Arc Radiation: The arc is a “miniature sun.” It emits intense ultraviolet (UV) radiation that will burn your eyes and skin. A quality auto-darkening welding helmet and full-coverage, flame-resistant clothing are mandatory.
• Electrical Shock: This is a high-amperage electrical tool. Never weld in wet conditions, and always check your cables and ground clamp for good connections.
• Fumes and Gases: Welding produces smoke and fumes. Always weld in a well-ventilated area, preferably with a fan or fume extraction.
• Fire and Burns: You are working with molten metal at thousands of degrees. Sparks can travel 30 feet. Always clear your workspace of all flammable materials (wood, paper, gasoline, etc.) and have a fire extinguisher nearby.

This Lincoln welder is a classic for a reason. It’s a simple, powerful, and reliable machine that has taught generations how to join metal. It represents an era of tool building where simplicity and durability were king. If you respect its power and embrace its learning curve, this “obsolete” box might just be the best tool you ever own.