ITI/NCVT Welder (Fab & Fit) (AITT Theory) common mistakes
ITI/NCVT Welder (Fab & Fit) (AITT Theory) · Understand the traps and how to avoid them.
Choosing an electrode current setting from memory of a 'typical' value for the electrode diameter instead of reading the manufacturer's recommended current range printed on the electrode packet or data sheet, then reporting that remembered number as the answer.
Trainees practice with one or two electrode sizes on one machine, so a single current value gets anchored as 'the' correct answer for that diameter; they do not realise the recommended range depends on electrode classification (e.g. E6013 versus E7018), coating type and polarity, and that exam questions test the range, not a personal habit.
What to do instead
Before answering any current-setting question, state the electrode classification and diameter, recall that the answer must be a range spanning roughly 10-20 A around a mid-value, and check whether the question specifies polarity and position, since vertical-up and overhead work use the lower end of the range. Build a personal table of classifications (E6013, E7018, E6010) against diameter with the low/mid/high current values and revise it until you can quote the range boundaries, not a single figure.
Describing a weld defect by its visual appearance only ('it looks like a crack') without naming the correct term, its position in the joint (toe, root, throat, HAZ) and its most probable cause, when the question asks for identification and cause.
Candidates learn defect names as a vocabulary list and match them to pictures, so they never link each defect to a mechanism: they cannot distinguish lack of fusion from lack of penetration, or porosity from a gas pocket formed by a specific contaminant, and they lose the cause-and-remedy marks.
What to do instead
For each defect build a three-column card: name and defining feature, location and how it is detected (visual, radiography, ultrasonic, bend test), and the process-specific cause with its remedy. Group them by mechanism instead of alphabetically: gas entrapment (porosity, blowholes), solidification (hot cracking, crater pipes), incomplete melting (lack of fusion, lack of penetration), and stress/geometry (lamellar tearing, distortion cracks). Practise writing the cause in process terms, e.g. 'damp E7018 electrodes and excessive arc length in SMAW', not 'bad welding'.
Reading a drawing's dimension as the finished size when the question involves a weld preparation or a fit-up allowance, and so giving a root gap, root face or edge preparation dimension that ignores the drawing's stated tolerance or the shrinkage allowance.
Trainees treat every number on a drawing as a single true value and forget that fit-up dimensions are nominal with tolerances, and that cutting and welding change the dimension; they also confuse the root gap with the root face and the included angle with the bevel angle.
What to do instead
Before calculating, annotate the drawing: mark which dimensions are finished-part sizes and which are preparation sizes, and write the tolerance beside each. Learn the standard single-V vocabulary as a set of four separate numbers (root gap, root face, included angle, bevel angle) and draw a sketch for each question. Where a shrinkage allowance is asked for, state the direction of contraction (transverse versus longitudinal) and apply the allowance to the dimension that actually changes.
Answering weld-symbol questions by describing the symbol's shape ('a triangle means a fillet') without stating the side of the joint, the arrow-side versus other-side rule, whether the symbol sits on a solid or dashed reference line, and the meaning of the tail and the size/length/pitch positions.
Symbols are memorised as pictures rather than as a positional code, so the candidate cannot say which side of the joint gets the weld, or confuses the size of a fillet (leg length) with its throat thickness, and misreads supplementary symbols such as the all-around circle or the field-weld flag.
What to do instead
Learn the reference line as a coordinate system: arrow side is below the line, other side is above, both sides means symbols on both; solid line means the arrow side of the joint, dashed means the other side. Then learn the standard left-to-right order of information on the symbol (size, then length and pitch after the symbol) and the tail for process or reference. Practise by taking ten symbol descriptions in words and drawing each, then reversing the exercise; the throat of a fillet is 0.707 times the leg, so check whether the question asks for leg or throat before answering.
Treating 'distortion control' as a single answer ('weld with less heat' or 'weld symmetrically') and giving only one technique when the question asks how a specific distortion type is prevented in a specific joint.
The topic is taught as a list of methods with no link to the type of distortion or the mechanism of residual stress, so candidates cannot select the appropriate technique: back-step welding, balanced welding, pre-setting, preheating, peening, stress relieving and fixture restraint all appear interchangeable to them.
What to do instead
Separate the two questions: residual stress (reduced by preheat, stress relief after welding, peening, low heat input, correct sequence) and distortion (controlled by pre-setting, balanced or back-step sequence, minimum passes, restraint, and allowing shrinkage direction). For each distortion type (longitudinal, transverse, angular, bowing, buckling) write the specific cause and the one or two methods that address it, then practise choosing between methods for a given plate thickness and joint, because thick sections need preheat and stress relief rather than peening.
Mixing up gas welding and cutting parameters: giving an acetylene pressure or a cutting-oxygen pressure for the wrong plate thickness, or confusing the neutral, oxidising and carburising flame and when each is used.
Candidates memorise 'about 0.5 bar' without the thickness context, and learn flame types from a picture without the oxygen-to-acetylene ratio or the application, so they cannot answer why a carburising flame suits aluminium or a slightly oxidising flame suits brass.
What to do instead
Learn flame types by ratio and consequence: neutral is roughly 1:1 oxygen to acetylene with a well-defined inner cone, oxidising has excess oxygen and a shorter hissing cone, carburising has excess acetylene with a feathery secondary cone and is used for high-carbon steel, aluminium and hardfacing. Learn that cutting is a separate process from welding: the cutting oxygen jet does the work and the heating flame only starts the cut, so cutting-oxygen pressure rises with plate thickness while the heating-flame pressures stay low. Tabulate nozzle size and pressure against plate thickness and revise the table, and always state the thickness in your answer.
Giving a single safety answer to a hazard question ('wear PPE') instead of naming the specific hazard, the specific control and the reason, and failing to separate the hazard from the control hierarchy.
Safety is revised as slogans, so candidates cannot match the control to the hazard: they answer 'use a screen' for a fume question or 'open a window' for an electric-shock question, and they miss that fume extraction, earthing of the return lead, flash screens, cylinder segregation and hot-work permits each address different hazards.
What to do instead
Build a hazard-control matrix: fume and gases (local exhaust ventilation, extraction at the arc, respiratory protection as a last line), radiation (screens, filter shade number matched to process and current), electric shock (earth the workpiece and return clamp, dry gloves, no damaged cable, isolated supply), fire and explosion (cylinder separation, flashback arrestors, hot-work permit, fire watch), and noise and burns. For each, state the hazard, the engineering control first, then PPE, and the reason; examiners award marks for the reason, not just the item.
Confusing TIG and MIG/MAG variables: using a constant-current characteristic or a scratch-start technique for the wrong process, or giving a shielding-gas flow rate and electrode polarity that belong to the other process.
Both are 'wire or rod plus gas' processes to a trainee, so the distinctions blur: TIG uses a non-consumable tungsten electrode with a separate filler and a constant-current supply, while MIG/MAG uses a consumable wire with a constant-voltage (flat) characteristic; polarity and gas differ too, and DCEP is standard for MIG/MAG while DCEN is usual for TIG on steel.
What to do instead
Learn each process as a fixed set of five attributes: power-source characteristic, electrode type and polarity, filler form, shielding gas, and typical current range. Write them side by side for SMAW, GTAW, GMAW and FCAW, and add the special cases (AC for TIG on aluminium, DCEP for MIG/MAG, self-shielded FCAW needing no external gas). When a question names a process, answer only in that process's attributes and check polarity and gas before finalising.
Answering inspection and testing questions by naming a test without matching it to the defect it can find, the joint type it suits, and whether it is surface or volumetric, or by confusing destructive with non-destructive methods.
The tests are learned as a list of acronyms (VT, PT, MT, UT, RT, bend, nick-break, macro) with no link to detectability, so candidates claim ultrasonic testing finds surface porosity or that dye penetrant works on any material, and they cannot answer which test proves root penetration.
What to do instead
Build a table with rows for each test and columns for what it detects (surface or internal), materials it suits (PT not for porous or rough surfaces; MT only for ferromagnetic materials), joint access needed, and typical weld application. Learn that bend and nick-break tests are destructive checks of procedure and workmanship, that radiography suits volumetric internal defects and ultrasonic suits planar internal defects such as lack of fusion, and that visual inspection comes first in every sequence. Answer by naming the test, what it detects and why it suits the stated joint.
Making fabrication and pipe/tube layout errors: calculating a bend allowance or a cut length without the neutral-axis radius, or marking a pipe branch without a wrap-around pattern, and giving a flat length that ignores the bend deduction.
Candidates use the outside or inside radius for the bend and forget that the neutral axis sits at about half the thickness, and they treat pipe branch marking as a linear measurement instead of a developed curve; they also forget to convert units and to account for kerf in shearing.
What to do instead
Learn the flat-length formula as three steps: bend allowance equals the angle in radians times the neutral-axis radius (inside radius plus half the thickness), then flat length equals the sum of the straight legs minus the bend deduction, with the deduction derived from the allowance and the setback. For pipe branches, learn that the branch intersects the main at a curve that must be developed and wrapped, and practise laying out a 90-degree branch on paper with a wrap-around strip. Always write the units at each step and check the kerf allowance in cutting and shearing questions.
Leaving employability and industrial-practice answers generic ('work as a team', 'follow instructions') when the question asks about a specific workplace behaviour such as 5S, a job card, a permit-to-work, or reporting a near miss.
The section is treated as filler and skimmed, so candidates cannot name the specific practice, its purpose or the correct sequence: they do not know what 5S stands for, what a hot-work permit authorises, or why a near miss is reported even when no one is hurt.
What to do instead
Learn each practice as a definition plus a purpose plus an action: 5S as sort, set in order, shine, standardise and sustain with the workshop benefit; permit-to-work as written authorisation for hot work with gas test, fire watch and isolation; near-miss reporting as recording an event that could have caused harm so the cause is removed. Practise converting each generic phrase into a named practice with a concrete example from a welding shop, and revise the standard first-aid and fire-extinguisher classes for a welding workshop.