NCCER Welding common mistakes
NCCER Welding · Understand the traps and how to avoid them.
Leaves the hot-work area immediately after the arc stops and treats the fire watch as a check for visible flames only.
Sparks and slag can ignite concealed or smoldering combustibles after welding stops, so the candidate confuses 'no flame now' with 'safe.'
What to do instead
Set the fire watch before hot work, clear combustibles or protect them, and continue monitoring during work and for at least the required post-work period, typically 30 minutes under hot-work permit rules.
Uses an oily wrench or a petroleum-based leak-test solution on oxygen regulator fittings.
Oxygen systems must be oil-free; grease or oil can ignite violently when exposed to high-pressure oxygen, but candidates often treat oxygen like compressed air.
What to do instead
Use only oxygen-clean fittings and an approved oxygen leak-test solution; never use oil, grease, or general-purpose soap on oxygen equipment.
Chooses an oxyfuel cutting tip by what fits the torch rather than by plate thickness, then uses the same oxygen pressure and travel speed for every cut.
Tip size, preheat, pressure, and speed are thickness-dependent; using one setup for all plate produces a ragged kerf, incomplete cuts, or excessive slag.
What to do instead
Use the manufacturer's tip chart for metal thickness, set the recommended pressures, preheat properly, and adjust travel speed to maintain a clean kerf and minimal drag.
Holds the cutting tip too high above the plate and travels too fast, then increases oxygen pressure to compensate for a ragged cut.
Excess standoff and speed prevent complete oxidation and washout; raising pressure masks the symptom and can worsen kerf quality.
What to do instead
Set the correct standoff for the tip, bring the plate to the proper preheat, and match travel speed to the cut; inspect kerf drag and adjust speed before changing pressure.
Cleans only the visible weld face and leaves mill scale, paint, oil, or rust on the joint faces and adjacent metal.
Contaminants in the joint produce porosity, incomplete fusion, and erratic arcs, and candidates often think the welding arc will 'burn through' surface dirt.
What to do instead
Clean joint faces and at least the adjacent base metal to bare, dry metal before fit-up; remove coatings, oil, rust, and scale, and re-clean after handling or grinding.
Calls a high-crowned, convex bead good reinforcement and does not evaluate bead profile, toe wetting, or hidden discontinuities.
Excess reinforcement can mask lack of fusion at the toes and is not a sign of a sound weld; candidates often judge quality by appearance alone.
What to do instead
Check bead profile against acceptance criteria, inspect toe lines and tie-ins, and relate visual defects to cause, such as current, travel angle, or travel speed, rather than accepting a 'full-looking' bead.
Selects electrode polarity from habit or from the color of the electrode coating instead of from the electrode classification and manufacturer data.
SMAW electrodes are designed for specific current types and polarities; for example, E6010 is commonly run DCEP while E7018 is commonly run DCEP or AC, and a wrong choice causes arc instability and poor fusion.
What to do instead
Read the electrode classification and follow the manufacturer's current and polarity recommendation; confirm the welding lead connection at the machine before striking an arc.
Runs a long arc and increases travel speed to keep the puddle small or to avoid sticking the electrode.
A long arc loses shielding and heat control, causing spatter, undercut, porosity, and lack of fusion; fast travel prevents proper tie-in at the joint edges.
What to do instead
Maintain an arc length approximately equal to the electrode core diameter, set current within the electrode range, and use a steady travel speed that keeps the puddle at the joint edges without undercutting.
Uses the same polarity and shielding-gas setup for self-shielded FCAW, gas-shielded FCAW, and GMAW because all are 'wire feed' processes.
The wire classification determines whether external shielding is required and which polarity is typical; self-shielded FCAW commonly uses no external gas and DCEN, while gas-shielded FCAW and GMAW commonly use DCEP with the specified gas.
What to do instead
Check the wire classification and manufacturer's data before setup; verify gas requirement, gas flow, and polarity, and do not assume every wire-feed process uses the same leads or gas.
Sharpens tungsten to a long, narrow point and uses it on aluminum with AC without checking the tip shape or contamination.
Tungsten preparation affects arc stability and current capacity; a long point can overheat or transfer tungsten, and contaminated tungsten causes an unstable arc and inclusions.
What to do instead
Grind tungsten longitudinally to the recommended taper for the current and material, keep a dedicated tungsten grinder, and for aluminum AC follow the machine or manufacturer's recommendation for balled or truncated tip shape; replace contaminated tungsten.