Sheet Metal Glossary: Fabrication Terms Defined
The terms that decide whether a flat pattern is right, a bend cracks, or a quote is comparable. Each entry is written the way our process engineers explain it to a customer — the definition first, then what it changes on the shop floor.
Thirteen terms that decide whether a flat pattern is right, whether a bend cracks, or whether a quote is comparable. Each entry gives the definition, the formula where there is one, and what the term actually changes on the shop floor.
Bend Allowance
The length of the neutral axis through a bend — the arc length you add to the flat legs to get an accurate flat pattern.
K-Factor
The position of the neutral axis inside a bend, expressed as a fraction of material thickness — the single number that makes a flat pattern correct.
Bend Deduction
The amount subtracted from the sum of the outside dimensions of a part to arrive at the correct flat length.
Springback
The partial return of the metal towards its original shape after the punch is withdrawn — the reason a bend comes out a few degrees shallower than commanded.
Kerf
The width of material removed by a cutting process — the gap the tool leaves behind.
Heat-Affected Zone (HAZ)
The band of material next to a cut or weld whose microstructure has been altered by heat, without being melted.
Progressive Die
A multi-station stamping tool in which each stroke performs one operation and the strip advances one station, delivering a finished part at the end of the line.
Deburring
Removing the sharp raised edge left by cutting or punching so the part is safe to handle and dimensions are reliable.
First Article Inspection (FAI)
A full dimensional and documentary check of the first part produced from a new tool or process, before production continues.
CMM Inspection
Dimensional measurement by probing points in three-dimensional space and comparing them to the CAD model or drawing.
PEM Insert
A threaded fastener pressed into a punched or drilled hole and locked there by displaced sheet metal, giving a permanent machine thread in thin sheet.
Grain Direction
The direction the metal was rolled in, which controls how far it can bend before it cracks.
Sheet Metal Gauge
A legacy thickness designation in which a larger number means a thinner sheet — and which means different things for different metals.
Turret Punching
Punching sheet metal with a CNC ram that indexes a turret of fixed tools — fast for holes and simple forms, and the process laser cutting mostly displaced.
Shearing
Straight-line cutting of sheet between a moving blade and a fixed blade — how a full sheet becomes blanks before any forming starts.
Press Brake
The machine that bends sheet metal: a punch presses the sheet into a V-die between two hydraulically or electrically driven rams, one bend at a time.
Air Bending
Bending with the punch stopped above the die walls — the angle is set by ram depth, one die covers many angles, and the tonnage is lowest of the three.
Bend Line
The straight line on a flat pattern where the bend starts — the reference every bending dimension, clearance rule and flat-pattern calculation is measured from.
Piercing
Driving a punch through sheet to cut a hole in one stroke — the hole material comes out as a slug, and the punch size is the hole size.
Blank
The flat, cut sheet piece that forming starts from — the part before it is bent, drawn or stamped into shape.
Strip Layout
The station-by-station plan of a progressive die strip — it decides material utilisation, pilot placement, die size and the cost of every thousand parts.
Transfer Die
Stamping with separate stations and a mechanical transfer system — for parts too large, too deep or too heavy for a progressive carrier to hold.
Compound Die
A die that blanks and pierces in a single stroke, with hole positions held by the tool — for flat parts where hole-to-blank accuracy rules the print.
Die Tryout
The controlled first runs of a new die, where springback, blank flow and pilot wear are corrected against real material before production release.
Weld Distortion
The shrinkage of weld metal as it cools, pulling the part out of square — planned around with sequence, heat input and fixturing, not fixed afterwards.
IP Rating
The IEC 60529 two-digit code for dust and water ingress — IP65 dust-tight and jet-proof, IP67 submersible. Earned by gasket and seam detail, not claimed.
EMC Shielding
A conductive, continuous enclosure that blocks interference — decided at seams, apertures and cable entries, and it must survive the finish.
Tolerance Stack-Up
How feature tolerances accumulate across a chain — three ±0.2 mm features can open a ±0.6 mm gap. Managed with datums, not by tightening everything.
Nesting
Arranging parts on a sheet so they cut in one pass — the layout that decides material utilisation, and a design outcome more than a software setting.
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