Welding Practice Test with Answers

Steel bend-test strip bent into a U at the weld, without cracks

This welding practice test has 55 questions with answers, on seven topics: safety, electricity and polarity, stick technique, rods and storage, MIG and flux core, TIG, and weld defects. Answer the question of the day or take a short quiz on one topic; every answer explains why and shows its source.

Checked by Randy Williams, welder for 16 years. Answers last checked on .

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Which fabric is the best choice for welding clothes?

  1. Polyester
  2. Nylon
  3. Wool or heavy cotton
  4. A waterproof rain shell
Show the answer

C. Wool or heavy cotton Natural fibers such as wool, cotton and leather smolder when a spark lands, so you can pat it out. Rain gear and other synthetics are the wrong choice for welding.

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Welding test questions and answers

Every question in the practice test, by topic. Open one to see the answer, why it’s right, and where it comes from.

Safety and protective gear

Which fabric is the best choice for welding clothes?
  1. Polyester
  2. Nylon
  3. Wool or heavy cotton
  4. A waterproof rain shell

Answer: C. Wool or heavy cotton. Natural fibers such as wool, cotton and leather smolder when a spark lands, so you can pat it out. Rain gear and other synthetics are the wrong choice for welding.

Source: Introduction to Welding 3.4; Introduction to Welding 3.5

Where should the legs of your work pants go?
  1. Tucked into your boots
  2. Over the top of your boots, not rolled or cuffed
  3. Rolled up above the ankle
  4. It doesn’t matter

Answer: B. Over the top of your boots, not rolled or cuffed. Pant legs go over the boots, and pants and sleeves are never rolled or cuffed, so sparks have nowhere to collect.

Source: Introduction to Welding 3.5

What should you take out of your pockets before you weld?
  1. A pencil
  2. A lighter
  3. A tape measure
  4. Soapstone

Answer: B. A lighter. Anything flammable, a lighter above all, comes out of your pockets before you strike an arc.

Source: Introduction to Welding 3.5

How should you choose the shade of your welding lens?
  1. The lightest shade that feels comfortable
  2. Start too dark to see the weld, then go lighter, never below the minimum
  3. Always use shade 14
  4. Any shade, as long as it is auto-darkening

Answer: B. Start too dark to see the weld, then go lighter, never below the minimum. Begin with a shade so dark you can’t see the weld zone, then step lighter until you can see it well, without going below the minimum for your process and amps.

Source: OSHA 29 CFR 1910.133; Introduction to Welding 3.2

Learn more: Welding lens shade chart

What is OSHA’s minimum lens shade for stick welding at 60–⁠160 amps?
  1. 5
  2. 8
  3. 11
  4. 14

Answer: B. 8. Shade 8 is the minimum from 60 to 160 A. The American Welding Society recommends 10–⁠12 in that range for comfort.

Source: OSHA 29 CFR 1910.133

Learn more: Welding lens shade chart

What is welder’s flash (arc eye)?
  1. A spark that lands in your eye
  2. A sunburn-like burn of the eye from the arc’s ultraviolet light
  3. An infection from welding fumes
  4. Glare that goes away when you look away

Answer: B. A sunburn-like burn of the eye from the arc’s ultraviolet light. Ultraviolet light from the arc burns the surface of the eye. It often hurts only hours later, and people walking past an arc can get it too.

Source: Introduction to Welding 3.2; Randy Williams, Welding Tribe

Learn more: Does welding hurt your eyes?

You lift your helmet to grind. What eye protection do you need?
  1. None, grinding is not welding
  2. Sunglasses
  3. Safety glasses and a clear face shield
  4. A dark shaded face shield only

Answer: C. Safety glasses and a clear face shield. With the hood up for grinding or cutting, you wear safety glasses and a clear face shield over them.

Source: Introduction to Welding 3.2

Is a paper dust mask enough protection from welding fumes?
  1. Yes, for any welding
  2. No: it only partly seals; ventilate, and use a NIOSH-certified respirator that seals
  3. Yes, but only outdoors
  4. Only for TIG welding

Answer: B. No: it only partly seals; ventilate, and use a NIOSH-certified respirator that seals. Ventilation comes first. A dust mask doesn’t seal around the nose and mouth; a respirator must seal, fit under the helmet and be NIOSH-certified, with N95 as the minimum filter.

Source: Introduction to Welding 3.7

Electricity and polarity

What kind of power do stick and TIG welders put out?
  1. Constant voltage (CV)
  2. Constant current (CC)
  3. Constant wattage
  4. High-frequency only

Answer: B. Constant current (CC). Stick and TIG run on constant current. MIG and flux core use constant voltage, so the machine holds the arc length for you.

Source: Introduction to Welding 5.1

With no voltage knob on a stick welder, how do you change the voltage?
  1. With the amperage knob
  2. With your arc length: a longer arc means more voltage
  3. With the rod angle
  4. You can’t

Answer: B. With your arc length: a longer arc means more voltage. On constant current, the arc length is your voltage control. Lengthen the arc and the voltage rises; shorten it and the voltage drops.

Source: Introduction to Welding 5.1; Introduction to Welding 8.4

What does a welding transformer do to the power from the wall?
  1. Raises the voltage and lowers the amps
  2. Lowers the voltage and raises the amps
  3. Raises both
  4. Turns DC into AC

Answer: B. Lowers the voltage and raises the amps. A welding transformer is a step-down transformer: it trades the wall’s high voltage for the high amperage welding needs.

Source: Introduction to Welding 5.2

DCEP used to be called…
  1. Straight polarity
  2. Reverse polarity
  3. Alternating polarity
  4. Ground polarity

Answer: B. Reverse polarity. DCEP (direct current, electrode positive) was called reverse polarity; DCEN (electrode negative) was straight polarity.

Source: Randy Williams, Welding Tribe

Learn more: Welding polarity chart

On DCEP, which terminal does the electrode holder go on?
  1. Negative
  2. Positive
  3. Either one
  4. It clamps to the work

Answer: B. Positive. Electrode positive: the holder goes on the positive terminal and the ground clamp on the negative. Most stick welding runs DCEP.

Source: Randy Williams, Welding Tribe

Learn more: How to hook up stick welding leads

Which polarity does most gasless (self-shielded) flux core wire use?
  1. DCEP
  2. DCEN
  3. AC
  4. Any of them

Answer: B. DCEN. Most gasless wires (E71T-⁠11, E71T-⁠8, E70T-⁠7) run electrode negative (DCEN); E70T-⁠4 runs DCEP, so check the spool. On the wrong polarity it spatters heavily.

Source: Miller Electric; Hobart Brothers

Learn more: Welding polarity chart

Which current do you use to TIG weld aluminum?
  1. DCEN
  2. DCEP
  3. AC
  4. Pulsed DCEN

Answer: C. AC. AC: the electrode-positive half cleans off the oxide and the electrode-negative half melts the metal. On DCEN the oxide stays and ends up in the weld.

Source: Miller Electric

Learn more: Welding polarity chart

What should you do before you change the polarity on a welder?
  1. Turn the machine off
  2. Run a test bead
  3. Turn the amps down
  4. Nothing

Answer: A. Turn the machine off. Switch the machine off first, whether you move the cables or flip a polarity switch.

Source: Randy Williams, Welding Tribe

Learn more: How to hook up stick welding leads

Why is welding in the rain dangerous?
  1. The rods dissolve
  2. Water conducts, so the current can flow through you
  3. The arc gets too hot
  4. It isn’t

Answer: B. Water conducts, so the current can flow through you. Wet skin, gloves and ground can make you part of the circuit instead of the ground clamp. Moisture also brings porosity and cracking.

Source: Randy Williams, Welding Tribe

Learn more: Welding in the rain

Stick welding technique

In stick welding, what does CLAMS stand for?
  1. Current, arc Length, Angle, Manipulation, Speed
  2. Clean, Light, Amps, Metal, Shade
  3. Current, Load, Arc, Metal, Slag
  4. Cable, Lead, Amps, Machine, Stinger

Answer: A. Current, arc Length, Angle, Manipulation, Speed. CLAMS is current, arc length, angle, manipulation and travel speed: the five things you control on every stick weld.

Source: Introduction to Welding 8.4

About how long should a stick welding arc be?
  1. The rod touching the plate
  2. About one rod diameter
  3. About an inch
  4. Three times the rod diameter

Answer: B. About one rod diameter. Hold a gap of about the rod’s diameter. Too long and the arc gets violent, spatters and undercuts; too short and the rod sticks and the bead rolls over cold.

Source: Introduction to Welding 8.4

Learn more: Welding troubleshooting

Which is a way to keep the rod from sticking when you strike the arc?
  1. Press the rod firmly into the plate
  2. A quick, light scratch, like striking a match, then lift to arc length
  3. Turn the amps down
  4. Hold the rod still on the plate until it lights

Answer: B. A quick, light scratch, like striking a match, then lift to arc length. Strike quickly and lightly: the harder you press, the more likely the rod sticks. Scratching is easier than tapping for beginners.

Source: Introduction to Welding 8.4; Randy Williams, Welding Tribe

Learn more: Why welding rods stick

The rod keeps sticking and the arc sputters as if it’s about to go out. What is most likely?
  1. Amps too high
  2. Amps too low
  3. Lens shade too dark
  4. Travel too slow

Answer: B. Amps too low. A hard start, constant sticking and a sputtering arc point to amperage that is too low.

Source: Introduction to Welding 8.4

Learn more: Stick welding amperage chart

The weld pool is long and shaped like a teardrop instead of an oval. What does that tell you?
  1. Amps too high
  2. Amps too low
  3. Arc too short
  4. The rods are damp

Answer: A. Amps too high. A long teardrop pool means the amperage is too high. Expect a flat, wide bead, undercut and spatter as well.

Source: Introduction to Welding 8.4

Learn more: Stick welding amperage chart

You see undercut, lots of spatter and a violent arc. What is the usual cause?
  1. Arc too long
  2. Arc too short
  3. Rod too small
  4. Wrong lens shade

Answer: A. Arc too long. A long arc runs hot and violent: it spatters and digs grooves along the edges. Bring it back to about one rod diameter.

Source: Introduction to Welding 8.4

Learn more: Welding troubleshooting

Your bead piles up and rolls over the edges of the joint. What should you change first?
  1. Travel faster
  2. Travel slower
  3. Hold a longer arc
  4. Use a bigger rod

Answer: A. Travel faster. Traveling too slowly lets the weld pile up and overlap the edges. Too fast does the opposite: a narrow bead and undercut.

Source: Introduction to Welding 8.4

Learn more: Welding troubleshooting

On DC, the arc keeps bending to one side near the end of the joint. Which fix helps?
  1. Move the ground clamp, or switch to AC
  2. Turn the amps up
  3. Hold a longer arc
  4. Weld faster

Answer: A. Move the ground clamp, or switch to AC. That is arc blow. Move the ground clamp or use more than one, switch to AC, use the lowest amps that work and hold a tight arc.

Source: Introduction to Welding 8.4

Learn more: Welding troubleshooting

Welding rods and storage

In E7018, what does the “70” mean?
  1. Run it at 70 amps
  2. At least 70,000 psi tensile strength
  3. 70% iron in the coating
  4. A 7.0 mm rod

Answer: B. At least 70,000 psi tensile strength. The first two digits give the weld metal’s minimum tensile strength in thousands of psi: 70 means 70,000 psi.

Source: Introduction to Welding 8.3

Learn more: Welding rod chart and number decoder

In E7018, what does the “1” (third digit) mean?
  1. All positions
  2. Flat position only
  3. One pass only
  4. DC only

Answer: A. All positions. A 1 in the third place means the rod welds in all positions. A 2 means flat and horizontal only.

Source: Introduction to Welding 8.3

Learn more: Welding rod chart and number decoder

Which rod has a deep, digging arc that copes with rust and dirt, and is used a lot for root passes?
  1. E6010
  2. E6013
  3. E7024
  4. E7018

Answer: A. E6010. E6010 digs deep and freezes fast, which suits root passes, tacking and less-than-clean steel. E6013 is the soft, shallow one for sheet metal.

Source: Introduction to Welding 8.3

Learn more: Welding rod chart and number decoder

Your welder only does AC. Which of these rods can you run?
  1. E6010
  2. E6011
  3. E7015
  4. None of them

Answer: B. E6011. E6011 is essentially E6010 that also runs on AC. E6010 and E7015 need DC electrode positive.

Source: Introduction to Welding 8.3

Learn more: Welding rod chart and number decoder

At what temperature should an opened can of 7018 rods be stored?
  1. Room temperature
  2. 100–⁠130°F
  3. 250–⁠300°F
  4. 700°F

Answer: C. 250–⁠300°F. Low-hydrogen rods are held in a rod oven at about 250–⁠300°F (120–⁠150°C) once the can is open. 700°F is for re-drying, not storage.

Source: Randy Williams, Welding Tribe

Learn more: Welding rod oven temperature chart

About how long can standard 7018 sit out of the oven before it picks up too much moisture?
  1. 30 minutes
  2. About 4 hours
  3. About a week
  4. As long as you like

Answer: B. About 4 hours. About 4 hours. Moisture-resistant rods (with an R in the name) can last about 9 hours. Take out only what you’ll use.

Source: Randy Williams, Welding Tribe

Learn more: Why welding rods need to be heated

What can moisture in low-hydrogen rods cause?
  1. Nothing, the arc boils it off
  2. Porosity and hydrogen cracking
  3. Deeper penetration
  4. A brighter arc

Answer: B. Porosity and hydrogen cracking. Moisture brings hydrogen into the weld, which leads to porosity and cracking, such as cracks at the toes.

Source: Randy Williams, Welding Tribe

Learn more: Welding rod oven temperature chart

Can you re-dry 7018 and 6013 together in the same oven?
  1. Yes, at the higher temperature
  2. Yes, at the lower temperature
  3. No, they need different temperatures
  4. Only for an hour

Answer: C. No, they need different temperatures. Don’t mix low-hydrogen rods with other rods when re-drying: each family has its own temperature range.

Source: Randy Williams, Welding Tribe

Learn more: Welding rod oven temperature chart

MIG and flux core

How far should MIG wire stick out past the nozzle, at most?
  1. 1/8 in
  2. 1/2 in
  3. 2 in
  4. 4 in

Answer: B. 1/2 in. No more than about 1/2 in. Longer stickout brings porosity and spatter.

Source: Miller Electric

Learn more: Welding troubleshooting

What is a typical shielding gas flow for MIG welding?
  1. 5–⁠10 CFH
  2. 30–⁠40 CFH
  3. 80–⁠100 CFH
  4. As high as the regulator goes

Answer: B. 30–⁠40 CFH. Lincoln Electric gives about 30–⁠40 CFH, set on a flowmeter. Too much flow is turbulent and pulls air into the weld.

Source: Lincoln Electric

Learn more: Welding troubleshooting

Which gas spatters less than straight CO2 for MIG on steel?
  1. 75% argon, 25% CO2 (C25)
  2. Pure oxygen
  3. Nitrogen
  4. Compressed air

Answer: A. 75% argon, 25% CO2 (C25). C25 spatters less than 100% CO2.

Source: Introduction to Welding 10.4

Which drive rolls does flux core wire need?
  1. Smooth U groove
  2. Knurled V groove
  3. Flat rolls
  4. Any rolls

Answer: B. Knurled V groove. Flux core wire is soft and hollow, so it needs knurled V-groove rolls. Smooth V groove is for solid steel wire, U groove for aluminum.

Source: Hobart Brothers; Introduction to Welding 9.2

Learn more: Welding troubleshooting

With flux core, should you push or drag the gun?
  1. Push
  2. Drag
  3. Hold it straight up
  4. It makes no difference

Answer: B. Drag. Drag it. Pushing lets slag run ahead and get trapped in the weld. Hobart gives 15–⁠45° of drag in most positions, 5–⁠15° vertical up.

Source: Hobart Brothers

Learn more: Welding troubleshooting

Worm tracks on a flux core bead usually mean…
  1. The voltage is too high
  2. The stickout is too short
  3. The wrong gas
  4. The wire speed is too high

Answer: A. The voltage is too high. Too much voltage for the wire speed. Lower it half a volt at a time until the marks stop.

Source: Hobart Brothers

Learn more: Welding troubleshooting

With the welding output off, you can stop the wire by pinching it at the gun. What do you do?
  1. Add drive roll tension
  2. Reduce drive roll tension
  3. Raise the voltage
  4. Change the gas

Answer: A. Add drive roll tension. If your fingers can stop it, the rolls are too loose: add tension until they can’t. Too much tension flattens the wire and causes birdnests.

Source: Lincoln Electric

Learn more: Welding troubleshooting

Your MIG arc makes a steady hiss and the weld undercuts. What is likely wrong?
  1. Voltage too high
  2. Voltage too low
  3. Gas flow too low
  4. The wrong drive rolls

Answer: A. Voltage too high. A steady hiss means too much voltage, which undercuts. A loud, raspy arc means too little. A good short-circuit arc buzzes steadily.

Source: Lincoln Electric

Learn more: Welding troubleshooting

TIG welding

Which shielding gas do you use to TIG weld steel?
  1. C25 (argon and CO2)
  2. 100% argon
  3. 100% CO2
  4. Oxygen

Answer: B. 100% argon. TIG uses pure argon (or argon-helium for thick aluminum). A MIG mix with CO2 contaminates the weld right away.

Source: Miller Electric

Learn more: Welding troubleshooting

What gas flow does Miller suggest for most TIG work?
  1. 5 CFH
  2. 15–⁠20 CFH
  3. 40–⁠50 CFH
  4. As much as possible

Answer: B. 15–⁠20 CFH. About 15–⁠20 CFH. More flow is not better: it becomes turbulent and pulls air in.

Source: Miller Electric; Introduction to Welding 11.2

Learn more: Welding troubleshooting

Your tungsten touches the weld pool. What should you do?
  1. Keep welding, it burns clean
  2. Stop and regrind or replace the tungsten
  3. Turn the gas up
  4. Switch to DCEP

Answer: B. Stop and regrind or replace the tungsten. Fix a contaminated tungsten straight away: welding on with it makes the arc wander and dirties the weld.

Source: Introduction to Welding 11.4

Learn more: Welding troubleshooting

How do you avoid a crack in the crater at the end of a TIG weld?
  1. Snap the arc off quickly
  2. Ease the current down while you keep adding filler
  3. Pull the filler away early
  4. Add more gas

Answer: B. Ease the current down while you keep adding filler. Stopping abruptly leaves a crater that can crack. Taper the current while still feeding filler, or use the machine’s crater fill.

Source: Miller Electric; Introduction to Welding 11.4

Learn more: Welding troubleshooting

Black flakes like pepper appear in your aluminum pool on AC. What helps?
  1. Give the AC balance more electrode-positive (cleaning) time
  2. Switch to DCEN
  3. Raise the gas to 40 CFH
  4. Use a MIG gas mix

Answer: A. Give the AC balance more electrode-positive (cleaning) time. The oxide isn’t being cleaned off. More electrode-positive time in the AC balance cleans it (on Miller-style controls, a lower balance setting); too much of it balls the tungsten.

Source: Miller Electric

Learn more: Welding troubleshooting

What should you clean aluminum with before TIG welding?
  1. The same wire brush you use on steel
  2. A stainless brush kept only for aluminum, right before welding
  3. Nothing, AC cleans it
  4. A grinding disc used on steel

Answer: B. A stainless brush kept only for aluminum, right before welding. Brush off the oxide just before welding with a stainless brush that is used on nothing else, so it carries no other metal onto the aluminum.

Source: Introduction to Welding 21.2; Miller Electric

The back of your stainless TIG weld comes out rough and crusty (sugared). How do you prevent it?
  1. Back purge the joint with argon
  2. Add more filler
  3. Raise the amps
  4. Use CO2

Answer: A. Back purge the joint with argon. Sugaring is oxidation on the back side. Shield it with an argon back purge, and keep the amps down.

Source: Miller Electric

Learn more: Welding troubleshooting

Weld defects and inspection

What is porosity in a weld?
  1. Gas pockets trapped in the weld metal
  2. Slag trapped between passes
  3. A groove along the edge
  4. A crack in the crater

Answer: A. Gas pockets trapped in the weld metal. Porosity is gas caught in the metal as it freezes, seen as pinholes on the surface or voids inside.

Source: Introduction to Welding 19.2; Miller Electric

Learn more: Welding troubleshooting

What is undercut?
  1. A weld that is too small
  2. A groove melted into the base metal along the toe and left unfilled
  3. Weld metal hanging below the joint
  4. Spatter under the weld

Answer: B. A groove melted into the base metal along the toe and left unfilled. Undercut is a groove melted beside the toe of the weld that the weld metal doesn’t fill. It weakens the edge of the weld.

Source: Hobart Brothers

Learn more: Welding troubleshooting

What is cold lap (overlap)?
  1. Weld metal that rolls over the edge without fusing to the plate
  2. A weld done in cold weather
  3. Two passes on top of each other
  4. A weld cooled with water

Answer: A. Weld metal that rolls over the edge without fusing to the plate. The weld spills over the toe and lies on the plate without melting into it, usually from traveling too slowly or welding too cold.

Source: Introduction to Welding 19.2; Miller Electric

Learn more: Welding troubleshooting

Why can a short-circuit MIG weld look good and still be bad?
  1. It can lack fusion that you can’t see
  2. MIG welds are always weak
  3. The color fades
  4. It can’t be bad if it looks good

Answer: A. It can lack fusion that you can’t see. In short-circuit transfer the pool can melt without fusing to the plate. It is hard to spot by eye, so it is checked with a bend test or ultrasonic testing. Dye penetrant only finds flaws that reach the surface.

Source: Lincoln Electric

Learn more: Welding troubleshooting

What is the most common cause of porosity in MIG welding, according to Lincoln Electric?
  1. Oil, rust, paint or grease on the metal
  2. Too much wire speed
  3. The wrong lens shade
  4. A low duty cycle

Answer: A. Oil, rust, paint or grease on the metal. Surface contamination comes first, then poor gas coverage. MIG has no slag to clean up dirt, so clean to bright metal.

Source: Lincoln Electric

Learn more: Welding troubleshooting

You strike the arc on the plate outside the joint. Is that a problem?
  1. No, it grinds off
  2. Yes: an arc strike is a discontinuity inspectors look for
  3. Only on aluminum
  4. Only with TIG

Answer: B. Yes: an arc strike is a discontinuity inspectors look for. Arc strikes outside the weld are listed among weld discontinuities. Strike the arc inside the joint, where the weld will cover it.

Source: Introduction to Welding 19.2

What helps prevent slag inclusions in a multi-pass weld?
  1. Cleaning every pass fully before the next
  2. Welding colder
  3. Pushing the gun or rod
  4. Skipping the root pass

Answer: A. Cleaning every pass fully before the next. Clean each pass, leave room for the next bead, drag rather than push, and keep the heat high enough for slag to float out.

Source: Hobart Brothers

Learn more: Welding troubleshooting

About the test

Who is this practice test for?

Welding students and beginners: the questions cover what a first welding course teaches, from safety and polarity to reading a bad weld.

Is this the welder certification test?

No. It is a study aid. Welder certification is a hands-on weld test taken at a test facility, not a quiz like this one.

How does the question of the day work?

Everyone gets the same question on the same day, and it changes at midnight your time. Answer one each day to build a streak.

Is my score saved?

Only in this browser on this device. Nothing is sent to Welding Tribe, and clearing your browser data resets it.

  • Questions written for Welding Tribe from the facts in “Introduction to Welding”, Washington State Board for Community and Technical Colleges, CC BY 4.0 (sections 3.2, 3.4, 3.5, 3.7, 5.1, 5.2, 8.3, 8.4, 9.2, 9.4, 10.4, 11.2, 11.4, 19.2 and 21.2). The textbook’s authors did not write or review them.
  • Lens shades: OSHA 29 CFR 1910.133(a)(5).
  • Lincoln Electric, “GMAW: Common MIG Problems and Remedies”; Miller Electric, “Tips for Troubleshooting Common MIG Weld Defects” and “Common TIG Welding Problems”; Hobart Brothers, “Troubleshooting Common Self-Shielded FCAW Problems”.
  • Randy Williams’s guides on this site: welding and your eyes, hooking up stick leads, welding in the rain, and heating rods.

Answers checked on by Randy Williams against the sources below. Spotted a mistake? Tell us.

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