Metalwork & finishing glossary.

A

Annealing

A heat treatment that softens metal and relieves internal stress: the metal is heated and then allowed to cool slowly. It makes a part easier to form or machine and reduces the risk of cracking.

Anodising

An electrochemical finish used on aluminium. It grows a hard, corrosion-resistant oxide layer into the surface, which can also be dyed in a range of colours. It's used on aluminium rather than steel.

B

Bend allowance

The extra length of flat material a fold consumes, because metal stretches around a bend. We calculate it from thickness, angle and inside radius so that a folded part finishes to the correct size — it's why a flat blank is slightly different in length from the sum of its folded faces.

Brake (press brake)

The machine that folds sheet metal. A top tool (the punch) presses the sheet down into a V-shaped die to form a crisp, repeatable bend. The press brake is what turns a flat laser-cut profile into a 3D bracket, tray or enclosure.

Brushed finish

A directional, satin texture made with abrasive belts or pads, leaving fine parallel lines. On mild steel it's usually sealed with lacquer to slow rusting; on stainless it's a popular standalone finish. See our care guide for looking after it.

C

Carbon steel (mild steel)

An iron-carbon alloy that is strong, easily welded and economical — the mainstay of most fabrication. It will rust if left bare, so it's normally powder coated, galvanised or lacquered. Our shop range is mostly 1.5–3mm mild steel.

CNC

Computer Numerical Control — a machine driven by a digital file rather than by hand. CNC cutting, folding and machining give precise, repeatable results, which is what lets us reproduce a part identically across a batch.

D

Deburring

Removing the sharp edges and small ridges (burrs) left behind by cutting, so parts are safe to handle and fit together cleanly. It's a standard finishing step before a part is folded, welded or coated.

DXF

Drawing Exchange Format — a 2D CAD vector file that describes flat profiles. It's the standard file we use to drive the laser. If you're supplying your own artwork, a clean DXF is the ideal format; see our guides for preparing one.

F

Flat pattern

The unfolded, flat outline of a part before it's bent, including the bend allowances. The laser cuts the flat pattern, then the brake folds it into the finished shape.

Fold (brake forming)

Bending sheet metal along a straight line to a set angle on a press brake. Folds make the flanges, boxes, brackets and trays that turn a flat sheet into a rigid 3D part.

G

Galvanising

Coating steel with zinc — most durably by hot-dip galvanising, where the part is dipped in molten zinc — to protect it from rust. It's the go-to protection for outdoor gates, railings and frames, and can be powder coated over the top for colour.

Gauge

A traditional numbering system for sheet thickness, where a higher gauge number means thinner metal. It's worth knowing because it still crops up, but modern fabrication usually quotes thickness directly in millimetres to avoid confusion.

Grain direction

The orientation of the rolling lines in sheet metal. Bends made across the grain are stronger and less likely to crack than bends along it, so we orient parts on the sheet with that in mind.

H

HAZ (heat-affected zone)

The band of metal beside a weld or cut whose properties have changed because of the heat, even though it didn't melt. Managing the HAZ matters for the strength and corrosion resistance of a finished joint.

K

Kerf

The narrow width of material removed by a cutting beam or blade. The laser automatically compensates for kerf so that finished holes and outlines hold their stated dimensions rather than ending up slightly undersized.

L

Laser cutting

Cutting flat metal with a focused, high-power laser beam guided by a CAD file. It's fast, accurate and leaves a clean edge, which is why it's the starting point for most of our parts. For cut-only work our sister site Andover Laser handles it.

M

MIG welding

Metal Inert Gas welding — a continuously fed wire electrode melts to join metal under a shielding gas. It's fast and well suited to mild steel fabrication, which makes it our workhorse for structural and production work.

Mill finish

The raw surface metal has as it leaves the mill, before any brushing, polishing or coating. It often carries light scale, oil or markings, so it's normally cleaned up and finished before a part is delivered.

N

Nesting

Arranging multiple parts efficiently on a single sheet before cutting, so as little material as possible is wasted. Good nesting keeps material costs — and therefore your price — down.

P

Pickling & passivation

A chemical treatment for stainless steel that removes scale and embedded iron, restoring the clean, corrosion-resistant surface — important after welding stainless, where the heat can leave it vulnerable to rust if untreated.

Plasma cutting

Cutting electrically conductive metal with a high-temperature ionised gas jet. It's useful for thicker plate, though the edge is coarser than a laser cut and usually needs more cleaning up.

Powder coating

A durable, even finish: dry powder is electrostatically sprayed onto the metal, then cured in an oven to form a tough, coloured film. It's available in matt, satin, gloss, hammered and textured grades and a wide range of RAL colours — our most popular finish for both shop and bespoke pieces.

Powder gun (electrostatic spray)

The handpiece that gives powder particles an electrical charge so they cling evenly to an earthed metal part. The charge is what lets powder wrap around edges and into recesses before the part is cured.

R

RAL

A European colour-matching standard. A RAL number — for example RAL 9005 jet black or RAL 7016 anthracite grey — names an exact colour, so a powder coat finish comes out consistent from one batch to the next and matches across separate parts.

S

Stainless steel

A steel alloyed with chromium so it forms a self-healing oxide layer and resists corrosion without coating. Common grades are 304 for general indoor and dry outdoor use, and 316 for marine, coastal or wet conditions.

STEP file

A neutral 3D CAD format (.stp / .step) used to share solid models of folded or assembled parts between different design programs. It's the format to send when geometry is three-dimensional rather than a flat profile.

T

Tack weld

A small, temporary weld that holds parts in alignment while they're checked, before the full continuous weld is run. Tacking lets us confirm a fit-up is square before committing to the final joint.

TIG welding

Tungsten Inert Gas welding — a precise, clean process using a non-consumable tungsten electrode with separate filler added by hand. It's ideal for stainless, aluminium and fine, visible work where the weld appearance matters.

Tolerance

The amount a finished dimension is allowed to vary from its nominal size. Tighter tolerances cost more to hold, so they're specified only where the fit genuinely demands it — tell us if a dimension is critical.

W

Weld spatter

Small droplets of molten metal thrown out during welding that stick to the surrounding surface. It's cleaned off as part of finishing so it doesn't show through paint or powder.

Z

Zinc primer

A zinc-rich paint applied before topcoat or powder to add sacrificial corrosion protection. It's especially worthwhile on parts that will live outdoors, giving an extra layer of defence under the colour.