SOLAS Metal Fabrication flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Datum edge

A single reference edge or face from which all dimensions are measured. Using one datum prevents cumulative measurement error that builds when each dimension is taken from the previous cut.

Saw kerf allowance

The width of material removed by the saw blade, roughly 1.5 mm for a hacksaw and 2–3 mm for a cold saw. It must be added to the required length when cutting stock.

Bend allowance formula

BA = θ(π/180)(R + K·T), where θ is bend angle in degrees, R inside radius, T thickness, and K the neutral-axis factor, typically 0.33 to 0.5.

Outside setback

The distance from the bend tangent point to the outside mould line, calculated as (R + T)·tan(θ/2). Two setbacks minus bend allowance gives the bend deduction.

Bend deduction

Flat-pattern shortening for one bend: bend deduction = 2 × outside setback − bend allowance. Flat length equals the sum of outside leg lengths minus this deduction.

Neutral axis factor K

The ratio locating the unstretched fibre within the material thickness during bending. K approaches 0.5 for large radius-to-thickness ratios and falls toward 0.33 for tight bends.

Minimum bend radius

The smallest inside radius that can be formed without outside-face cracking. Guide values are about 1T for mild steel and 1–2T for aluminium and austenitic stainless.

Hole-to-bend clearance

Holes should sit at least 2T plus the inside radius from the bend line. Closer placement lets the hole stretch into an oval and distorts the finished part.

Worst-case tolerance stack

For n chained dimensions each with tolerance ±t, the maximum possible total variation is ±n·t. This arithmetic sum is used for fits and safety-critical assemblies.

Root-sum-square tolerance stack

A statistical stack where total variation equals ±t·√n for n dimensions of equal tolerance. It predicts typical assembly variation but not the absolute worst case.

Temper colour straw

A pale straw oxide tint on polished steel indicating roughly 220 °C. It corresponds to the tempering range for high-carbon cutting tools that need maximum hardness retention.

Temper colour blue

A blue oxide tint on steel indicating roughly 300 °C. It signals a spring-temper range where hardness is reduced but toughness is improved compared with straw.

Abrasive wheel speed limit

Every bonded abrasive wheel carries a maximum safe peripheral speed or rpm. Exceeding it can burst the wheel, so the machine spindle speed must never exceed the marked rating.

Welding fume extraction

Local exhaust ventilation capturing fume at the arc. It is required for indoor arc welding because chromium and manganese in fume pose chronic respiratory and neurological risks.

Fire watch duration

A person stationed to watch for ignition during hot work and for at least 60 minutes after it ends, with a further check of the area before leaving the site.

Sling leg tension

For a two-leg sling with included angle 2α, each leg tension = load / (2·cos α). A 120° included angle makes each leg carry the full load.

Flashback arrester

A device fitted to both torch lines that stops a flame from travelling back into the hose or regulator, protecting the cylinder from internal ignition.

Cylinder storage separation

Oxygen and fuel-gas cylinders are stored upright, kept at least 3 m apart or divided by a fire-rated barrier, and secured against falling.

Back-step welding

A distortion-control technique where each weld bead is started ahead of the previous one and run back over it, spreading heat input and reducing angular shrinkage.

Balanced welding sequence

Alternating welds about the neutral axis of the joint, such as opposite sides of a fillet, so shrinkage forces cancel and the part stays straighter.

Presetting against shrinkage

Deliberately setting the joint at an angle opposite to the expected shrinkage direction before welding, so the finished part pulls back to the required flatness.

Vernier calliper resolution

A measuring tool reading external and internal sizes to about 0.02 mm. It is suited to general fabrication checks but not to precision shaft tolerances.

Micrometer use

A precision instrument reading to 0.01 mm, used for shafts and thickness where calliper resolution is insufficient. The ratchet thimble controls measuring force.

Feeler gauge

A set of thin steel leaves of known thickness used to measure gaps and clearances, such as valve lash, joint root gaps, or fit between mating surfaces.

Dial indicator runout

A gauge with a spring-loaded plunger that shows small displacement on a dial. Rotating a part against it reveals eccentricity, runout, or shaft misalignment.

Drawing precedence

The rule that a fabrication drawing governs over general specifications, which govern over standard practice. Conflicts are raised as a technical query before material is cut.

Nonconformance report

A record raised when a part falls outside drawing tolerance or an approved rework allowance, documenting the deviation and the disposition decision rather than hiding it.

Witnessed competence sign-off

Apprentice assessment where a qualified person observes the task and records it only when the finished work meets the drawing tolerance and process specification.

Chained dimensioning

Dimensioning each feature from the previous one rather than a common datum. Each tolerance adds to the last, so error accumulates along the part.

Baseline dimensioning

Dimensioning every feature from one common datum so tolerances do not accumulate. Preferred for parts with several related holes or faces.

Springback

The elastic recovery of metal after the bending force is removed. It is compensated by over-bending and increases with higher yield strength and larger bend radius.

Heat input per unit length

Arc energy delivered per millimetre of weld, calculated as (voltage × current × 60) / (travel speed in mm/min × 1000), in kJ/mm. It controls cooling rate and distortion.