MMA Welding Diagram Explained: Circuit, Parts, Polarity & Setup Guide

A first-year apprentice once told me he spent two hours trying to strike an arc because his boss had handed him a machine with the leads swapped — the electrode holder was clamped to negative and the earth lead to positive on an E6010 rod that needed DCEP. Nothing in the machine was broken; the diagram in his head was simply wrong. That is exactly why understanding the MMA welding diagram matters: every stick weld you will ever make is governed by the circuit, the components and the polarity drawn in that simple-looking schematic.

What Is an MMA Welding Diagram and Why Does Every Welder Need One?

If you have spent any time in a fabrication shop, you have heard the same process called three different things. An old-school welder says “stick,” a welding inspector says “SMAW,” and a college textbook says “MMA.” They are all describing Manual Metal Arc welding: a consumable, flux-coated electrode that carries the current, strikes the arc, and melts into the joint to become the weld metal. In AWS/ANSI terminology it is Shielded Metal Arc Welding (SMAW); in shop slang it is stick welding; in European and ISO documents it is MMA. Same process, three names, one diagram.

An MMA welding diagram is the schematic that shows how that process actually works on paper. It maps the welding circuit (power source, cables, holder, electrode, arc, workpiece, and earth clamp), the direction of current flow, the polarity of the terminals, and often the joint geometry the weld is being made into. It is the picture that lives behind every dial setting and every electrode choice you make at the machine.

Who Actually Searches for This Term, and Why?

The people looking up “MMA welding diagram” are rarely browsing for fun. They are usually:

• Students and apprentices preparing for theory exams where they must draw or label the welding circuit and explain polarity.
• DIYers and hobbyists who just bought a stick machine and are staring at two leads, two terminals, and a pile of rods, unsure what connects where.
• Technicians and maintenance workers troubleshooting a machine that arcs poorly, burns rods, or won’t strike at all.
• Fitters and layout workers trying to decode joint details and weld symbols on a fabrication drawing before the torch ever comes out.

All four groups are really asking the same question: what is supposed to be connected to what, and what happens to the current when it gets there?

Three Different Diagrams People Confuse

Part of the confusion is that “MMA welding diagram” can mean three genuinely different drawings, and mixing them up causes real mistakes on the shop floor.

A welder who can read all three is a welder who can set up a machine, strike a stable arc, and produce a joint that passes inspection. This article walks through all of them, one layer at a time.

Why Standardized Diagram Language Matters

Diagrams only work if everyone reads them the same way. The American Welding Society, founded in 1919, has spent more than a century advancing the science and application of welding worldwide, and it is AWS that standardizes the terminology, symbols, and classifications that appear on welding diagrams in the United States and beyond. When a drawing says E7018, DCEP, or a fillet weld symbol on the arrow side, there is exactly one correct interpretation, and it is the same in every shop that follows AWS standards. Free references like the Open Washington welding textbook chapter on SMAW are a good starting point for students who want the formal definitions behind the sketch.

The safety side of the diagram is not merely advisory, either. OSHA groups MMA welding hazards under 29 CFR 1910 Subpart Q for general industry and 29 CFR 1926 Subpart J for construction, which means the ventilation, PPE, and electrical protection elements shown on a welding diagram are legally regulated requirements. The helmet, gloves, leathers, fume extraction, dry work area, and insulated holder are not optional accessories drawn in for decoration; they are the compliance layer of the schematic. Our Welding PPE: The Complete Guide to Protective Gear Every Welder Needs covers that layer in depth, and OSHA’s own welding, cutting, and brazing fact sheet summarizes the core hazards you are protecting against.

If you are brand new to the process and wondering whether stick welding is even worth learning, our honest take is in Is Stick Welding Hard? An Honest Beginner’s Guide. Spoiler: the machine is easy to understand. The diagram, once it clicks, makes the rest of it make sense.

With the definitions settled, we can start tracing the actual current path, component by component, exactly as it appears on the schematic.

Anatomy of the MMA Welding Circuit: A Part-by-Part Diagram Walkthrough

Strip away every label on an MMA welding diagram and you are left with one idea: a loop. Current leaves the power source, travels down a cable, passes through the electrode holder into the consumable rod, jumps the arc into the workpiece, then climbs back through the earth clamp and return cable to where it started. Break that loop anywhere and the arc dies. Understand it fully and most “mysterious” stick welding problems stop being mysterious.

The Series Loop, Step by Step

Trace the circuit in the order the current actually flows:

1. Power source. The machine that converts incoming supply into welding current. Older units use a transformer plus rectifier diodes; modern inverters use electronics to switch at high frequency, giving a lighter box and finer control.
2. Welding lead (secondary cable). Carries current from the machine to the holder. It is short, flexible and heavily insulated because it handles hundreds of amps.
3. Electrode holder, or stinger. The insulated clamp that grips the bare end of the rod and delivers current into it.
4. Consumable electrode. The rod itself: a core wire that melts into the weld pool, wrapped in a flux coating that shields and stabilises the arc.
5. The arc. The plasma gap between rod tip and metal. This is where the electrical energy becomes heat, typically around 6,000 °F or more at the arc core.
6. Workpiece. The parent metal, which carries current away from the puddle.
7. Work clamp (earth/ground clamp). Bolted or clamped to the workpiece close to the weld, it collects the returning current.
8. Return cable to the power source. Completes the loop back to the machine.

If any element in that chain is missing or poor, the circuit pays for it. A rusty, loose earth clamp forces current through a resistive contact, the arc wanders, the machine sputters, and the clamp itself gets hot enough to burn the operator.

Why Amperage Ratings Must Match

Every component in the diagram carries an ampere rating, and those ratings must meet or exceed the machine’s maximum output. Undersized cables have too little copper cross-section for the current, so resistance turns the jacket into a hot, sagging hazard and the lost voltage never reaches the arc. That voltage drop shows up as a soft, unstable arc even though the dial reads correctly.

Guidance from the American Welding Society’s educational materials and trade references is consistent: match lead gauge to output, inspect insulation, and keep connections tight. The same logic applies to holders and clamps. A 300 A-rated holder on a 200 A machine is fine; a 100 A holder on a 200 A machine is not, and the overheating usually starts at the jaw contact rather than the cable.

The U.S. Occupational Safety and Health Administration is explicit on this point: 29 CFR 1926.351(a) requires manual electrode holders to be specifically designed for arc welding and cutting and rated for the maximum current they will carry. The rule exists because undersized and generic holders are a documented ignition and shock hazard on job sites.

Connector quality deserves its own mention, because the quick-disconnect points between cable and machine are a frequent failure zone. If you are choosing or replacing them, our guide to welding connectors explained covers selection, installation and the signs of a bad joint.

Where the Primary Side Fits

Do not confuse the two halves of the diagram. The primary side is the incoming supply feeding the machine: wall receptacle, plug, breaker or generator. The secondary side is the welding circuit you just traced. A correctly sized welding lead means nothing if the primary circuit is starving the machine, so technicians read both sides when troubleshooting. On generator-driven sites, this is the most common cause of an arc that “worked yesterday.”

Finally, remember that the same loop logic appears across processes: the current path in how a spot welder works is a closed secondary circuit too, just clamped rather than struck as an arc. Once you can read the MMA diagram as one continuous loop with rated components, you can diagnose most setup faults before you ever strike the rod.

Reading Polarity on the Diagram: AC, DCEP and DCEN Explained Simply

Polarity is the single most misread line on an MMA welding diagram. It looks like a tiny ‘+’ or ‘–’ next to a terminal, yet it decides whether your arc digs deep or sits on the surface, whether your root run burns through, and why a rod that ran beautifully yesterday refuses to cooperate today.

What the Symbols Actually Mean

On a DC machine, the diagram marks two terminals: the negative (–) post and the positive (+) post. Cables connect to them, and the polarity is defined by which terminal the electrode is attached to, not which one the work clamp sits on. That distinction is exactly where the apprentice in our opening story went wrong.

• DCEN (Direct Current Electrode Negative), historically called DCSP (Direct Current Straight Polarity): the electrode is on the – terminal, the work clamp on the +. Electrons flow from the electrode into the workpiece.
• DCEP (Direct Current Electrode Positive), historically called DCRP (Direct Current Reverse Polarity): the electrode is on the + terminal, the work clamp on the –. Electrons flow the other way, out of the workpiece toward the electrode.

Those old names still appear on older machine faceplates, WPS documents and trade-school handouts, so it pays to know both vocabularies. TWI’s technical guidance on MMA electrode polarity confirms the naming: DCEP was historically referred to as Direct Current Reverse Polarity, and DCEN as Direct Current Straight Polarity. If your diagram says DCRP or DCSP, it means exactly the same thing as DCEP and DCEN respectively.

Where the Heat Goes

On DCEN, roughly two-thirds of the arc heat concentrates at the workpiece side, giving a broad, shallower bead. On DCEP, more heat stays at the electrode tip, producing a more focused, penetrating arc. In practice, according to TWI:

• DCEP generally gives greater penetration — useful on heavier joints where you want to avoid lack of fusion between passes.
• DCEN gives reduced penetration and lower dilution of the weld metal with the base metal — which is exactly what you want on an open root run where burn-through is the enemy.

This is why a thin-gauge stick welding thin metal job often behaves better on DCEN with a fast-freeze rod like E6010, while a heavily beveled structural joint runs more comfortably on DCEP or a low-hydrogen E7018.

AC: The Compromise Setting

AC alternates polarity many times per second, splitting its behaviour roughly between the two. It’s the fallback when you’re welding dirty, rusty or painted steel and the arc keeps wandering, or when you’re running an AC-only rod such as a cellulose-sodium E6011 on an AC/DC machine. The trade-off is that AC is generally less stable than DC on a given electrode and gives neither the full penetration of DCEP nor the gentle root behaviour of DCEN.

Electrode Compatibility: Check Before You Strike

Not every rod runs on every current. Most common stick electrodes carry their recommended current in the AWS classification, which we decode in the next section. Some run AC/DC, some are DC-only, and a few are AC-only. Running a DC-only low-hydrogen rod on AC usually means a rough, sputtering arc and contaminated weld metal.

Before every job, confirm three things against your diagram: which terminal the electrode holder is on, which current your electrode requires, and whether your WPS allows either polarity. Our practical walkthroughs on 3/32 E7018 amperage and polarity and electrode selection show how much difference this single decision makes in real settings. Get polarity right on the diagram, and the arc will usually tell you the rest.

The Electrode and Its Diagram Notation: Decoding AWS A5.1 Classifications

The electrode is the one part of an MMA circuit that is both conductor and consumable, and on shop drawings it never appears as a picture. It appears as a code. Reading that code is the difference between grabbing the right rod off the rack and spending an hour fighting an arc that was never meant to run the way you are running it.

How Electrodes Show Up on Diagrams and Spec Sheets

On an equipment layout diagram the electrode is usually a line labelled with its classification, something like E7018, 1/8 in, DCEP. On a fabrication drawing the process sits in the tail of the welding symbol, and the filler metal classification travels with the welding procedure specification that governs the job. The diagram tells you where the rod goes; the classification tells you what the rod is, what current it wants, and what positions it can legally be welded in. For the long version of rod selection, our guide to electrode types, numbers and polarity walks through the whole family tree.

Decoding E6010, E6011, E6013 and E7018

The American Welding Society publishes the classification system under AWS A5.1, the specification for carbon steel electrodes for shielded metal arc welding. A full designation such as E7018 breaks down into four positions, plus optional suffixes:

• E — electrode. It conducts current from the holder into the arc.
• First two digits (60, 70, 80…) — the minimum tensile strength of the deposited weld metal in thousands of pounds per square inch. E60xx rods produce weld metal rated at 60,000 psi; E7018 produces 70,000 psi. That is why E7018 is the default structural rod on mild steel.
• Third digit (position) — 1 means all-position, weldable flat, horizontal, vertical and overhead. 2 means flat and horizontal only, common on iron-powder rods like E7028 that deposit fast in the downhand position. 4 covers flat, horizontal, vertical-down and overhead, a key distinction for positional work such as overhead fillet and groove welds.
• Fourth digit (coating and current) — the chemical family of the flux covering, which dictates compatible current. This is where E6010, E6011, E6013 and E7018 part ways.

Lincoln Electric publishes an excellent AWS electrode classification chart that expands this into every digit and suffix, and it is worth printing and pinning above your rod rack. For practical settings on the most common structural rod, see our deep dive on 3/32 in E7018 amperage and polarity.

Suffixes: H4, H8, H16 and R

Real-world designations rarely stop at four digits. A rod stamped E7018-H4 carries a maximum diffusible hydrogen of 4 millilitres of hydrogen per 100 grams of deposited weld metal. The scale runs H8, H4, H2 and H1, with lower numbers meaning drier weld metal and less susceptibility to hydrogen-induced cracking. Because low-hydrogen coatings absorb moisture from the air, rods also carry an R designator for a moisture-resistant covering that can be stored longer before baking, and many carry an -1 suffix indicating compliance with an impact-toughness requirement at low temperature.

This suffix work matters on the diagram more than beginners realise. An E7018 rod that has sat out in a humid shop is functionally a different electrode from the one the WPS approved, which is why low-hydrogen rods come sealed in plastic and get held in a rod oven. Getting hydrogen control wrong shows up later as cracking, and the crack usually gets blamed on technique.

The Practical Takeaway for Reading Your Diagram

When you read the electrode callout, three questions answer themselves instantly. What tensile strength am I depositing? What positions can this rod run in? What current does the machine need to be set to? If the drawing says E7018 on DCEP and the machine is wired DCEN, you are not just making a weak weld, you are making a fundamentally wrong one, which brings us back to the polarity symbols in the previous section. Once the code becomes second nature, the diagram stops looking like hieroglyphics and starts looking like instructions.

Joint Design and Groove Diagrams: Where the MMA Diagram Meets the Blueprint

Everything so far has been electrical. But the first drawing your boss hands you in a fabrication shop usually isn’t a circuit schematic at all — it’s a blueprint covered in arrows, angles and small numbers running along a joint. That is the other half of the term “MMA welding diagram,” and it is the half that decides whether your part fits after it cools.

The Five Basic Joints Every Drawing Uses

Every joint you will ever weld is one of five arrangements. Fabrication drawings assume you recognise them on sight, because the symbol sitting on the arrow tells you what to do with that joint, not which joint it is.

Butt and T joints carry the vast majority of structural MMA work. The OpenWashington welding joints chapter walks through these configurations with the same terminology used on shop drawings.

Groove Preparations: Where Metal Gets Removed

Worth memorising: AWS describes a groove weld as a weld made in the groove between two members, where metal has been removed from one face (a single-groove weld) or from both faces (a double-groove weld). Remove it from one side and you get a single-V, single-bevel or single-U. Remove it from both and you get a double-V or double-bevel, which lets you weld from alternating sides on thick plate and keep distortion balanced.

The groove types that show up on MMA drawings are:

• Square groove — edges butted flush with no bevel; thin material or heavy backing.
• V-groove — both members angled into a V; the workshop default for plate.
• Bevel groove — only one member is angled, the other stays square.
• U-groove — curved faces, less filler volume on very thick sections.
• J-groove — one side curved, one square.
• Flare-V and flare-bevel — the groove formed by the natural radius of rolled shapes or bent plate, not by cutting.

Reading the Numbers Along the Joint

Four dimensions do most of the work, and mixing them up is a classic apprentice error:

• Root opening — the gap between the members before welding. Too tight and you get lack of fusion at the root; too wide and the arc blows through, which is exactly what our stick welding thin metal guide warns about on light gauge.
• Groove angle — the total included angle of the groove. If the drawing says 60°, both bevels share it at 30° each on a symmetrical V.
• Bevel angle — the angle cut into a single member. A 30° bevel each side makes the 60° included angle.
• Depth of bevel / depth of preparation — how far down from the face the cut runs, usually leaving a small root face (land) of about 1/16–1/8 in at the bottom. It matters when only part of the thickness is machined and the rest stays square.

On pipe drawings the same numbers appear alongside schedule and wall thickness, which is why pipe welding procedures spend so much time on fit-up tolerances: a perfect root pass is impossible if the root opening closes up as you tack.

Fillet Welds: Leg Size Versus Throat

On T, lap and corner joints the drawing gives a fillet size, and that size means leg length, measured from the joint root to the toe of the weld. The dimension that actually carries load is the throat: for an equal-leg fillet with a flat profile, theoretical throat = 0.707 × leg, so a 1/4 in fillet has a theoretical throat of about 0.177 in. A convex fillet adds metal above that line; a concave one, common in overhead work, can leave the actual throat below the nominal figure. That is one reason overhead stick welding technique focuses so heavily on controlling heat and profile.

Which Joints Suit MMA Best

MMA handles thick section, positional and root-pass work beautifully: butt grooves in plate and pipe, structural T joints, and any joint exposed to wind where shielding gas is unreliable. It is slower and messier on thin sheet and on high-volume flat production, where MIG or submerged processes earn their keep. In practice, most MMA drawings you see will be a butt groove, a T-joint fillet, or a corner joint on heavier plate — master those three and you can read most of what comes out of the shop.

How to Read AWS Welding Symbols on MMA Drawings (A2.4 Reference)

A welder I once trained could run a textbook 3G root pass but went blank the moment a fabricator handed him a print. The symbol was a simple fillet with a number and a small flag; he guessed the leg size and burned a weld that failed visual inspection before lunch. Reading symbols is not office work. The symbol is the only place on the drawing that tells you what to weld, where to weld it, how big it must be, and under which procedure.

In the United States the authority behind those symbols is ANSI/AWS A2.4, Standard Symbols for Welding, Brazing, and Nondestructive Examination. The current edition, ANSI/AWS A2.4:2012, governs American fabrication, pressure vessel and structural drawings. Whether you are studying for an exam, writing a WPS or reading a shop print, A2.4 is the rulebook you are being tested against.

The Four Anchors of Every AWS Symbol

Every AWS symbol is built from four parts, and once you can spot them you can decode almost anything:

• Reference line. The horizontal backbone that everything hangs from. AWS uses a single reference line.
• Arrow. The leader pointing from the reference line to the joint. The side it touches is the arrow side; the far side is the other side.
• Weld symbol. The geometric shape (fillet, groove, plug and so on) sitting above or below the line. This tells you the type of weld.
• Tail. The forked bracket at the end of the line, drawn only when you need to note a process, specification or WPS number, such as SMAW, A5.1 E7018. No tail, no special process note.

Arrow Side and Other Side: The Rule That Catches Everyone

This is the single most tested rule in A2.4, and the most misread one in the shop:

• A symbol placed below the reference line means the weld goes on the arrow side.
• A symbol placed above the reference line means the weld goes on the other side.
• Symbols on both sides mean weld both sides, sized independently.

Note what does not matter: the direction the arrow points. Rotating the arrow does not flip the symbol. Only the position relative to the reference line decides.

Basic Weld Symbols You Will See on MMA Prints

Groove welds require metal removed from one or both faces to create the preparation; fillets do not. Spot symbols belong to resistance-welded sheet assemblies, which is why it helps to understand how a spot welder works before assuming every circle on a print belongs to your stick machine.

Dimensions, Length, Pitch and the Little Flags

• Size, left of the symbol. For a fillet, the leg size. For a groove, the depth of preparation; a second number to the right is the effective throat.
• Length, after the symbol. The weld length in inches.
• Pitch, in parentheses. Intermittent welds at that center-to-center spacing. 3 (10) reads as 3-inch welds at 10-inch centers.
• Weld-all-around. A small circle at the arrow-and-reference-line junction means weld the entire perimeter, common on pipe-to-flange and tube work.
• Field weld. A small flag at that same junction means the weld is made on site, not in the shop.
• Contour and finish. A straight line above the symbol means flush, convex means reinforcing, concave means underflush. A letter alongside names the finishing method, such as G for grinding or C for chipping.

ISO 2553 vs AWS A2.4: Why International Prints Confuse American Welders

European and international drawings follow ISO 2553, which uses dual reference lines: one solid, one dashed. The symbol sits on the solid line for the arrow side or on the dashed line for the other side. AWS A2.4 uses a single reference line and relies entirely on above-or-below placement. Read an ISO drawing with AWS assumptions, or the reverse, and your weld lands on the wrong side of the joint. If you see a dashed line running parallel to the reference line, stop and confirm the standard before you strike an arc.

For a visual walkthrough of the symbol elements, Miller’s guide to reading and understanding weld symbols is an excellent companion, and the National Board’s welding symbol reference is the one pressure vessel inspectors rely on.

Worked Example and the Mistakes That Cost You a Rework

Take a fillet triangle below the reference line, “1/4” to its left, “3 (P 8)” to its right, and a flag at the arrow junction. That reads: a 1/4-inch leg fillet on the arrow side only, 3 inches long at 8-inch centers, welded in the field. Read it again before setting the machine, because the usual shop errors are all symbol-reading errors: reversing arrow side and other side, missing the all-around circle on a tubular joint, ignoring the tail and loading the wrong rod, skipping a stated root opening, or treating an ISO dashed line as an AWS tail. For pipe work especially, symbols tie straight into the WPS, passes and inspection plan in our pipe welding procedures guide.

The habit that fixes all of this takes thirty seconds: find the reference line, identify the arrow side, check for the all-around circle and field flag, read the tail, then confirm size and length. Do that on every joint and the print stops being a puzzle. And once you know the joint a symbol calls for, our stick welding sheet metal guide shows how that changes your amperage and rod choice.

MMA vs MIG, TIG and FCAW: How the Diagrams Differ

All four of these arc welding processes do the same job: pushing current through an arc to fuse metal. However, when you look at their circuit diagrams, the hardware drawn tells a very different story. Being able to spot those differences at a glance is one of the fastest ways to read any shop schematic.

The MMA Diagram: One Consumable, No Gas Bottle

The most stripped-back of the four is MMA (SMAW). A standard diagram will only show a power source, two leads, an electrode holder, a bare-end stick electrode, an arc, a workpiece and an earth clamp. What isn’t there matters just as much: no gas cylinder, no regulator, no flow meter and no gas hose.

That’s because the flux coating around the electrode provides its own shielding. As it heats, it creates a protective gas envelope and leaves behind a slag layer. With everything it needs attached to the consumable, the electrical side is all that matters. For that reason, TWI’s guidance on MMA electrode polarity focuses on current and electrode selection, not gas delivery.

MIG and MAG: The Wire-Feed Expansion

Swap that stick for a continuous spool of solid wire and you’ll need to feed it. A MIG (GMAW) or MAG diagram will add a wire feed motor, drive rolls, a spool, a gas solenoid valve, a gas cylinder and a hose running from the regulator to the gun. Polarity is also usually set to DCEP, with the gun on positive and the work clamp on negative.

For most mild steel work, an external shielding gas such as a 75% argon / 25% CO₂ mix is used. All of those added fittings create more potential leak points, so setup is more involved. Our MIG welder setup guide covers that process in full, and our welding connectors explainer breaks down the hardware that holds it all together.

TIG: Precision With a Separate Filler

A TIG (GTAW) diagram looks minimal, but its key change is the electrode. The tungsten in the torch is non-consumable, meaning it carries current without becoming part of the weld. The filler rod is drawn separately and fed by hand with no electrical connection. Paired with an argon cylinder and current control, such as a torch valve or foot pedal, this gives precise heat control. For thinner materials, that control is crucial, which is exactly what our TIG sheet metal guide focuses on.

FCAW: The Best of Both Worlds

Flux-cored arc welding (FCAW) reads like MIG on a schematic. It still uses a spool, drive rolls and a continuously fed gun. The difference is the wire: a hollow steel tube filled with flux instead of solid wire. From there, it splits into two variants:

• Gas-shielded FCAW (FCAW-G): Keeps the cylinder and hose for external shielding, much like MIG.
• Self-shielded FCAW (FCAW-S): Removes them entirely, as the flux inside generates its own shield. This is the wire-feed equivalent of MMA.

These distinctions are reflected in electrode designations, and structural flux-cored wires conform to AWS A5.20. For real-world runs, check out our flux core wire welding tips.

Reading the Diagram in Practice

When scanning an unfamiliar schematic, use this three-point check: look for a cylinder, a wire spool and the electrode. No cylinder and a bare-end stick means MMA. Cylinder plus wire means MIG or gas-shielded FCAW. Tungsten with a separate filler rod means TIG.

That simplicity is also why MMA shines in the field. It’s wind-resistant, tolerates dirty or rusty plate and only requires two cables and a power source, making it ideal for remote work. For those runs, our 3/32 E7018 settings, 5/32 E7018 guide, overhead stick welding handbook and pipe welding procedures guide cover the techniques in depth.

Setting the Machine: Amperage, Arc Voltage and Electrode Diameter Charts

Knowing the circuitry of an MMA welding diagram is one thing, but translating it to the dials on your machine is another. Many beginners stare at an amperage knob, a few symbols, and feel lost. With a few reliable rules, you can match your diagram to real settings with confidence.

The 1 Amp per 0.001 Inch Rule

The most consistent starting point for mild steel is the rule of thumb: 1 amp of current for every 0.001 in of electrode diameter. For example, a 1/8 in rod (0.125 in) typically starts around 110 to 130 A, a 3/32 in rod (0.094 in) around 80 to 100 A, and a 5/32 in rod (0.156 in) around 140 to 160 A.

This range is a guide, not a fixed number. Joint prep, position, material thickness, and root passes will all shift it. For thinner stock, lower the amperage to prevent burn-through. For thick plate in the flat position, you can move closer to the top end. If you’re working with very thin material, our dedicated article on stick welding thin metal goes further into the adjustments needed.

Reference Settings: E6013 and E7018

Two electrodes cover most everyday jobs. E6013 is a rutile rod that runs smooth on AC or DCEP at moderate amperage, making it ideal for sheet metal. E7018 is a low-hydrogen electrode best known for its strength in structural work, commonly run on DCEP or AC. Use these ranges as a starting baseline:

For a closer look into the reasoning behind these numbers, check out our guides on 3/32 E7018 amperage and 5/32 E7018 amperage, covering polarity and technique in more depth.

Stick-Out, Arc Voltage and Open-Circuit Voltage

Stick-out is the bare length of electrode from the holder tip to the arc. A good starting point is roughly equal to the core diameter of the electrode. Shortening it slightly increases current, while lengthening it decreases amperage and raises arc voltage.

With MMA, arc voltage isn’t directly dialled like MIG. Instead, open-circuit voltage (OCV) plays the biggest role. Older transformer machines sit around 60 to 80 V OCV, while modern inverters provide a higher striking voltage with less power draw, allowing for much easier starts, especially with E7018. For proper polarity selection based on your electrode, refer to TWI’s guidance on electrode polarity selection.

Hot Start and Arc Force on Inverter Panels

Many modern inverter machines introduce two settings not found on classic transformers:

• Hot start – A short amperage boost at the moment of strike. This helps prevent the rod from freezing, but should be lowered when welding thin material to avoid blow-through.
• Arc force – An automatic amperage boost when the arc shortens. It’s useful for root passes and out-of-position work, but too much can create excessive spatter.

Treat these as fine-tuning tools. Get your amperage, polarity, and electrode choice correct first. To better understand electrode classifications before choosing, our electrodes explained guide is a great resource to reference.

Finally, no dial setting can compensate for poor preparation. Keep your work clamp secure, cables in good condition, and PPE intact. Start conservatively, run a test bead on scrap, adjust only one variable at a time, and let the bead tell you if your interpretation of the diagram was correct.

Safety Layer of the Diagram: PPE, Ventilation and Electrical Protection

Every MMA welding diagram carries an invisible layer on top of it. The schematic shows where current flows, but it does not announce the ultraviolet radiation, molten spatter and metal fumes that arc is about to produce. Treating safety as part of the drawing rather than an afterthought is what keeps a controlled weld from becoming an emergency.

PPE: The Barrier Between You and the Arc

Start at the operator. A stick arc at 100 amps produces enough UV to burn cornea tissue in seconds, so shade 10 is a common minimum helmet shade for MMA work, rising to shades 11 to 13 for higher amperage and out-of-position runs. Auto-darkening lenses are convenient, but a fixed-shade passive lens never fails on you with a dead battery.

Gloves must be full-leather gauntlets, not thin TIG gloves, because stick spatter lands and stays. Flame-resistant leathers, a cap under the helmet and safety glasses worn underneath complete the base kit. Our guide to welding PPE and protective gear breaks down every item and why it matters.

Ventilation: The Part of the Diagram You Cannot See

Shielding is not a concern in MMA the way it is in MIG or TIG, but fume is. Stick electrodes release oxide fumes containing manganese, chromium and nickel depending on the base metal and coating. OSHA’s fact sheet Controlling Hazardous Fume and Gases during Welding (FS-3647) points employers to the general welding, cutting and brazing standards in 29 CFR 1910 Subpart Q and 29 CFR 1926 Subpart J, all built on one rule: ventilation first, respiratory protection second.

The numeric requirement in construction is 29 CFR 1926.353: where general ventilation cannot hold contamination below acceptable limits, mechanical local exhaust must be used, and where that is still not enough, welders must wear respiratory protection. Practically, that means welding upwind where you can, holding a fume extractor arm close to the arc, and moving air across the workspace rather than letting fume pool at head height.

Why This Layer Got Stricter

The stakes changed in 2017, when the International Agency for Research on Cancer reclassified welding fume as a Group 1 carcinogen. Reviews since have repeatedly noted that welders carry roughly a 40% greater risk of lung cancer than workers in other professional groups. None of that appears on a schematic, which is why ventilation belongs on your checklist every single job, not only when the bay smells bad.

Respiratory decisions should never be improvised either. Our MIG welding safety precautions guide applies the same fume principles to wire processes, and those habits carry straight over to stick.

Electrical Protection on the Circuit

Back on the schematic itself, three components carry safety duties:

• Insulated cable. The secondary leads run at low voltage but high current, so cracked insulation or an exposed conductor near the work clamp is both a shock and a fire hazard. Size cables to the machine’s output, keep them out of walkways and inspect them before every session, as we cover in welding connectors and cable care.
• Insulated electrode holder. The stinger body must be undamaged and fully closed around the electrode, so the live end cannot be touched accidentally during repositioning.
• Work clamp placement. Clamp to clean, sound metal as close to the joint as possible. A clamp on painted or rusty plate forces current through a poor path, causing arcing at the clamp, overheating and burns where you do not expect them.

Dry Conditions and Fire Watch

Water and welding leads do not mix: damp floors, wet gloves and sweaty hands all lower the effective resistance between you and the circuit. Work on dry boards, keep the machine off wet ground and never drag cables through puddles. On the other side of the hazard ledger, spatter ignites what you cannot see, so clear a radius around the work, cover combustibles, and post a fire watch with an extinguisher for at least 30 minutes after the final arc. Hot slag smoulders quietly.

Add these habits to the circuit you learned in the anatomy section and the diagram becomes complete: current path, component path, and the human path that keeps all of it survivable.

Common MMA Diagram Mistakes, Troubleshooting Fixes and Practice Tips

You can memorize every symbol in a schematic and still burn a hole through your workpiece on Monday morning. Almost every stick welding problem traces back to one thing: the diagram in the welder’s head doesn’t match the diagram in the machine. These errors are repeatable, recognizable, and fixable once you know what to look for.

The Six Mistakes That Ruin Good Joints

• Reversed polarity. The single most common setup error. An E7018 wants DCEP; an E6013 runs happily on AC or DCEP. Swap the leads and you get weak penetration, excessive spatter, or an arc that simply won’t stay lit. Check the ‘+’ and ‘–’ terminals against your electrode’s classification before you strike. Our guide to electrode types, numbers and polarity breaks down which rods accept which current.
• A dirty, rusty, or badly placed work clamp. The hidden saboteur of arc stability: the work clamp closes the secondary circuit, and if it’s clamped to paint, mill scale, rust, or a thin flange that can’t carry return current, the arc wanders, stutters, and stalls even though your rod and amperage are perfect. Clean a bright metal spot, clamp close to the joint, and confirm the cable is tight at the lug. Loose connectors cause the same symptom; properly installed cable connectors matter as much as the rod in your hand.
• Undersized or overextended cables. A 4/0 lead on a 250 A machine is fine; two runs of 2/0 at 40 feet are not. Voltage drop heats the cable instead of the arc, and the diagram’s “ideal conductor” becomes a glowing resistor.
• Welding on galvanized, painted, or oily base metal. Beyond the porosity and inclusions, burning zinc produces the classic metal fume fever chills and nausea. Grind, wipe, or chemically clean the joint zone first. The same discipline applies to avoiding undercut and other defects that thrive on contaminated edges.
• Misreading the arrow side. On an AWS symbol, a bevel groove symbol placed on the arrow side means the bevel goes on the member the arrow points to. Put it on the other side and your fitter has machined the wrong plate. Always confirm against the fabrication drawing before tack-up, especially on procedural pipe welds where rework is expensive.
• Skipping the root opening. A tight-fit butt joint with no root face or gap gives you a cold, unfused root, and no amount of amperage fixes geometry you never created.

Troubleshooting Table: Symptom, Diagram Cause, Fix

Practice That Actually Builds Skill

Run beads on plate in all three positions before you ever touch a joint. Write the polarity, electrode, and amperage on the back of each coupon so you can correlate appearance with settings. Deliberately run one weld with a badly placed clamp, then one with it properly seated; the difference teaches you more than any paragraph. Keep the safety layer non-negotiable: helmet shade, leathers, ventilation, and dry footing are part of the circuit too, because a welder who gets hurt stops the current faster than any machine. Our welding PPE guide covers the full kit, and burn prevention and first aid is worth reading before your first long session. OSHA’s hazard and ventilation standards make the same point from the regulatory side (OSHA welding, cutting and brazing hazards; 29 CFR 1926.353).

The bottom line: an MMA welding diagram is not decoration. It defines the power source, cables, electrode holder, consumable, workpiece, return clamp, polarity, joint geometry, and the symbol language on the drawing. Read it before you set the machine, and nine out of ten “bad rod” complaints disappear. If stick still feels intimidating, our honest beginner’s guide to stick welding sets realistic expectations, and the rest of this series fills in the detail for every step.

Frequently Asked Questions

What is an MMA welding diagram?

What is the difference between MMA and SMAW?

Which polarity should I use for MMA welding?

What do the numbers in an AWS electrode classification like E7018 mean?

How do I read a welding symbol on an MMA drawing?

What size electrode and amperage should I start with?

Why is my arc unstable even though the machine is on?

Does MMA welding need shielding gas?

What are the main safety hazards shown around an MMA welding diagram?

Where can I find the official standard for welding symbols?