Metalworking Glossary: Cutting, Grades, Finishing and Ordering Terms Explained

Metal suppliers use a lot of shorthand, and it is easy to feel lost when a spec sheet mentions temper, kerf or a grade code you have never seen. This metalworking terms glossary gives you a plain English definition of each one, with a more technical note where it helps. The terms are grouped by theme, so the page reads naturally from cutting through to ordering, and where we already have a full guide, we link to it rather than repeat it.

• Alloy
• Anodising
• Bar Against Rod
• Box Section
• Brushed Finish
• BS/EN Grade Designation
• Chamfer
• CNC Cutting
• Cut-to-Size
• Deburring
• Ductility
• Extrusion
• Ferrous
• Flat Bar Against Strip
• Galvanising
• Gauge
• Guillotine Cutting
• Kerf
• Laser Cutting
• Malleability
• Mill Finish
• Non-Ferrous
• Passivation
• Patina
• Polished Finish
• Powder Coating
• RHS
• Sheet Against Plate
• SHS
• Temper
• Tensile Strength
• Tolerance
• Yield Strength

Group 1: Cutting and Fabrication Terms

Every project starts with a cut, so this first part of the metalworking terms glossary covers the words you are most likely to meet when metal is sized and prepared.

Kerf

What is kerf? Kerf is the width of material removed by the cutting process itself, such as the thin slot left behind by a saw blade. It matters because the finished piece always ends up slightly smaller than the stock it came from, so a cutting list needs to allow for it whenever several pieces are taken from a single length.

Tolerance

Next, what is metal tolerance? Metal tolerance is the amount a finished measurement is allowed to vary from the size you ordered. Our general cutting tolerance is + or - 2mm, which keeps parts accurate without holding up your project. For a fuller explanation, read our guide to what metal cutting tolerance means for your project.

Deburring

Deburring is the removal of the sharp, raised edge (known as a burr) that cutting can leave behind. Because a burr can catch on skin or snag against a neighbouring part, smoothing it makes the piece safer to handle and easier to fit.

Chamfer

A chamfer is a small, angled edge cut onto a corner in place of a sharp right angle. It is used for safety, because it removes a point that could catch or cut, and for finish, because it gives the piece a neat, deliberate edge.

CNC Cutting

CNC stands for computer numerical control, and CNC cutting means a machine follows a programmed path to cut the metal. The result is consistent, repeatable accuracy from one piece to the next, which makes it a good fit when several parts all need to match.

Laser Cutting Against Guillotine or Shear Cutting

Laser cutting uses a focused beam to melt through the metal, which allows fine detail, curves and intricate shapes with a clean edge. Guillotine cutting, also called shear cutting, uses a straight blade to slice through sheet along a line, which is quick and well suited to straight-edged pieces.

In practice, the finish and tolerance you get depend on the machine, the material and its thickness, so the right method is the one that suits the shape you need. Guillotine cutting is one of the services we offer here at Click Metal.

Group 2: Material and Grade Terms

These terms describe what a metal is made of and how it will behave when you bend, load or fix it, so they are worth understanding before you settle on a grade or thickness.

What Does Gauge Mean in Metal?

Gauge is a non-metric way of describing thickness, and you will still see it on some spec sheets and older supplier documents. The catch is that a higher gauge number means thinner metal, and the same number can mean a different thickness depending on the metal and the gauge standard used.

For example, 16-gauge steel is roughly 1.5mm, while 16-gauge aluminium is closer to 1.3mm. It is therefore safest to convert to millimetres before you order, and if you are unsure, our team can help.

What is Metal Temper?

Temper describes the heat-treatment or work-hardening state of a metal, usually shown as a code such as H14 or T6. It affects both strength and formability: a harder temper is stronger but less forgiving when bent, while a softer one is easier to shape. If you plan to fold or form aluminium, it is worth checking the temper before you order.

Tensile Strength and Yield Strength

Tensile strength is the most pulling force a metal can take before it breaks, while yield strength is the point at which it starts to bend permanently and will not spring back. Put simply, yield strength tells you when a part begins to deform and tensile strength tells you when it fails. For most projects, yield strength is the more useful figure, because a part that has bent out of shape has usually stopped doing its job.

Ductility and Malleability

Ductility is how far a metal can be stretched or drawn out, for example into wire, before it breaks. Malleability is how far it can be hammered, rolled or pressed into shape without cracking. Both describe how forgiving a metal is when it is bent or formed, so a metal that scores well on both is generally easier to work by hand.

Alloy Against Pure Metal

A pure metal contains only one element, whereas an alloy is a metal blended with other elements to change its properties. Aluminium is a good example: 1050A is close to pure, which makes it soft and easy to form, while 6082 is alloyed with elements such as magnesium and silicon, which makes it considerably stronger. Our UK aluminium grades comparison shows how the common grades stack up.

Ferrous Against Non-Ferrous

Ferrous metals contain iron, while non-ferrous metals do not, and that difference affects both rusting and magnetism. Most ferrous metals will rust if left unprotected and are magnetic, so mild steel needs a coating or paint, whereas aluminium and brass are non-ferrous and resist rust.

Stainless steel is ferrous too, although its chromium content gives it strong corrosion resistance and, in some grades, only weak magnetism. If you are choosing between grades, our guide to stainless steel grades explained shows how they differ.

Sheet Against Plate

In this sheet metal glossary, the key point is thickness. Sheet is the thinner product, and plate is the thicker one, with the dividing line commonly sitting at around 3mm. The distinction matters when you order because thickness affects how the metal is cut and handled, which is why our services include both guillotine cutting and aluminium plate sawing. If your project falls close to 3mm, check the stated thickness rather than relying on the name alone.

Group 3: Finishing and Coating Terms

Finishing terms describe the surface of a metal and any treatment applied to it. This part of the metalworking terms glossary begins with the two coatings people most often compare.

Anodising

Anodising is an electrochemical process that thickens the natural oxide layer on aluminium, making the surface harder and more resistant to wear and corrosion. Unlike paint, the layer becomes part of the metal itself. You can see how it measures up in our full guide to anodising vs powder coating.

Powder Coating

Powder coating is a finish in which dry coloured powder is applied to the metal and then baked, forming a tough, even layer in a wide range of colours. It sits on top of the surface rather than becoming part of it. For a side-by-side look, read our article on which aluminium finish lasts longest.

Galvanising

Galvanising is the process of coating steel with zinc to protect it from rust. Hot-dip galvanising lowers the steel into molten zinc, which builds a thick, durable layer, while electro-galvanising uses an electric current to apply a thinner, smoother layer of zinc. If you are weighing up anodising vs galvanising meaning, the short version is that anodising treats aluminium, whereas galvanising protects steel.

Mill Finish

Mill finish is the natural, unfinished surface a metal has straight from production. It can show light marks or slight variation from one batch to the next, and it can always be painted, polished or coated later if you want a different look.

Brushed Finish and Polished Finish

A brushed finish has fine parallel lines that give a soft, matt appearance and help hide fingerprints and light scratches. A polished finish is smooth and reflective, which looks striking but shows marks more easily. The satin effect you see on kickplates and kick strips is a brushed-style finish, so it is a practical choice for surfaces that get regular use.

Patina

Patina is the natural surface change that some metals, particularly brass and copper, develop over time as they react with air and moisture. It can add depth and character, although some people prefer to polish brass regularly to keep it bright.

Passivation

Passivation is a chemical treatment used on stainless steel after fabrication to restore its corrosion resistance. Cutting and machining can leave tiny traces of free iron on the surface, and passivation removes them so that the protective chromium oxide layer can form again.

Group 4: Ordering and Specification Terms

These last terms are the ones you will see on product pages and order forms, which is where a small misunderstanding can cost the most time.

Cut-to-Size

Cut-to-size means the metal is cut to the exact length and width you specify, rather than supplied as a standard stock length that you trim yourself. At Click Metal, we offer this service as standard, with a general tolerance of + or - 2mm and no minimum order charge, so there is less waste and no extra cutting to do at your end.

Box Section, RHS and SHS

Box section is hollow metal tube with a square or rectangular cross-section. RHS stands for rectangular hollow section and SHS for square hollow section, so SHS is simply the square version of box section and RHS the rectangular one. Both are popular for frames, supports and furniture because they are strong for their weight.

Flat Bar Against Strip

Flat bar is rectangular metal that is thicker, and it is used where strength or stiffness matters, such as brackets, frames and supports. Strip is thinner and often supplied in narrower widths, which suits trim, edging and lighter work. There is no single universal cut-off between the two, so check the stated thickness and width rather than relying on the name.

Bar Against Rod

Bar is a general term for solid lengths of metal in profiles such as round, square, hexagonal or flat, whereas rod usually means a thinner, round solid length. The two words are often used loosely, and some suppliers treat them as interchangeable, so go by the stated diameter and profile instead of the name.

Extrusion

Extrusion is a process in which heated aluminium is pushed through a shaped opening, called a die, to form a long section with a constant profile. It is how aluminium channel, angle and tee sections are made, and it means one profile can be produced in long lengths and then cut to your size through our extrusion cutting service.

BS/EN Grade Designation

A BS/EN grade designation is the letter-and-number code that identifies a metal's composition and properties under British (BS) or European (EN) standards, such as EN AW-6082 for an aluminium alloy. You do not need to memorise the system. Our metal grade and specification reference hub explains how to read it.

Finding the Right Term for Your Order

That covers the main terms you are likely to meet when specifying metal, from kerf and tolerance through to finishes and grade codes. Keep this metalworking terms glossary handy while you browse, and when you are ready to choose your sizes, you can order online from our shop with every piece cut to your measurements.

If a term on a drawing or spec sheet is not listed here, we are happy to explain it. Give us a call on 01794 526090 or fill out our online contact form, and we’ll answer any questions you have.