NSSCO Metalwork and Welding 6188 common mistakes
NSSCO Metalwork and Welding 6188 · Understand the traps and how to avoid them.
Leaves the chuck key in the drill chuck, or leaves a spanner on the lathe chuck, and starts the machine without a final check.
Under time pressure the candidate treats the key or spanner as part of the setup and relies on memory rather than a fixed pre-start routine.
What to do instead
Use an attached or spring-loaded chuck key where available, and make a deliberate 360-degree visual and tactile sweep of the chuck and machine before pressing start.
Identifies a metal as mild steel from surface colour alone, then chooses welding current or a heat-treatment cycle from that guess.
Rust, mill scale, paint and galvanising disguise the surface, and the candidate takes the quickest visual shortcut instead of comparing behaviour.
What to do instead
Compare an unknown sample with known samples using a spark test on a grinding wheel and a file test for hardness; remove coatings before welding or heat treatment.
Marks every dimension from a different edge of the workpiece instead of from one datum, and checks square only after cutting.
The candidate treats each edge as equally reliable and does not allow for edge damage, burrs or accumulated marking error.
What to do instead
Establish one true datum edge and one datum end, mark all dimensions from those, and check the try square against a straight edge before any cutting.
Uses a file without a handle and keeps pressure on during the return stroke.
The candidate copies a quick workshop habit and does not connect the missing handle to the risk of the tang piercing the hand.
What to do instead
Fit a correctly seated handle before filing, apply pressure on the forward stroke only, and lift the file slightly on the return stroke.
Drills thin sheet with a standard 118-degree twist drill, without a centre punch and without clamping the sheet.
The standard drill has an aggressive chisel edge, and the candidate underestimates how quickly thin sheet grabs and tears.
What to do instead
Centre-punch the hole, clamp the sheet to a backing board, and use a sheet-metal drill, step drill or reduced-point-angle drill at the correct speed.
Calculates a flat pattern by adding only the outside dimensions, ignoring bend allowance and bend radius, so the folded part comes out short or the holes misalign.
The candidate treats sheet as zero thickness and does not visualise the neutral axis moving during bending.
What to do instead
Calculate bend allowance from the neutral-axis formula, mark bend lines from the same datum, and make a test bend in scrap before cutting the final blank.
Quenches a carbon-steel chisel from a bright orange heat straight into water without normalising or tempering it.
The candidate confuses hardening with the complete heat-treatment cycle and believes a harder tool is always a better tool.
What to do instead
Normalise first, harden from the correct austenitising temperature, then temper immediately to the required colour; use oil where the steel grade requires a slower quench.
Solders a copper joint after only wiping the surface, or keeps the soldering iron on the joint until the flux turns black.
The candidate thinks wiping removes contamination, and believes more heat always improves flow.
What to do instead
Abrade the joint to bright metal, apply fresh flux, heat the workpiece until solder melts on contact, and remove the heat before the flux burns.
Runs a stick electrode with a long arc and fast travel over dirty mill scale, producing undercut, poor penetration and slag inclusions.
The candidate fears sticking the electrode and rushes the bead instead of cleaning the joint and setting a stable current.
What to do instead
Clean the joint to bright metal, set current to the electrode manufacturer's range, hold an arc length close to the electrode diameter, and remove slag between passes.
Starts cutting and folding from a freehand sketch without a cutting list or orthographic views, and mixes first-angle and third-angle projection on the drawing.
The candidate is eager to make the project and does not check the projection symbol or plan the sequence of operations.
What to do instead
Produce a dimensioned drawing with the correct projection symbol, a cutting list, datum dimensions and bend lines; verify the drawing and sequence before cutting material.