Metalwork

[edit] Introduction

Metalwork is a general term for the act or process of shaping items from metal either by hand or by machine, as such it covers a broad range metal related activities. It is also used to describe final items after processing, these metalwork items can range from fine crafts and jewellery to railings and structural building elements.

[edit] Metal cutting

Cutting metal is a primary part of working with it. Different methods achieve different accuracy, types of cuts and finish:

Milling - a process of removing precise amounts of metal using a rotating cutting or scraping machine. A mill rotates whilst the object being cut is fixed, a CNC mill is the same but computer controlled.

Turning- a process of removing precise amounts of metal linearly by turning the item on a fixed blade. A lathe (also found in metal work shops) uses this process, which can make use of CNC machines to do similar tasks.

Grinding- using abrasion to remove material, normally at the later finishing stages of processing. Bench grinders are fixed machines whilst angle grinders are hand held. Modern CNC machines can perform similar tasks.

Drilling- a drill press or handheld drill, with a lubricant makes accurate holes. CNCs can also do this.

[edit] Metal joining

Joining is required to build anything of more than a single piece or type of metal:

Welding - a process that joins various materials through pressure and heat. There are 5 different ways to weld, Flux, Paslma-arc,Oxy-acetylene, Stick or Arc, TIG and MIG welding.

Soldering -a fine process that joins various materials by melting a filler metal using a soldering iron or a gas-powered torch. It creates an electrical bridge and is used in electronics, plumbing and general metalwork.

Riveting- a hot or cold process using metallic cylinders with a head on one end driven through a hole to create a permanent mechanical fixing. It is used for structural elements for buildings, such as high rise steel frames.

[edit] Metal forming

Forming is required to create products from single or multiple metals and involves one of the oldest metalwork crafts:

Forging- a hot process used to form and shape metal with a forge and hammer such as by a blacksmith. Forging can also be carried out as a cold process using pressure to form shape (also called cold forming)

Roll forming- a hot or cold process that continuously bends a long strip of sheet metal through a roll forming mill. Hot-rolled steel means that the steel is rolled after being heated to above it's recrystallization temperature.

Rolling- a hot or cold process that continuously thins metal through a roll forming mill producing sheets or strips of a desired thickness. Cold-rolling can improve the uniformity and finish of the sheet material.

[edit] Metal casting

Reusable permanent moulds - made of a preheated metal with a higher melting point than the metal being cast. Fluid metal is poured into mould, no pressure, must simple and not thin. so it can be withdrawn.

Reusable semi-permanent moulds - same as above but the cores might be non reusable and do not need to remain in tact. Often a sand core can be shaken or vibrated free from the cast.

Reusable slush casting - hollow castings made without the need for cores by coating the inside of the mould with a metal layer or skin that sets.. Zinc, aluminium, and pewter are metals often use this approach.

Reusable centrifugal casting - a symmetrical mould such as a tube is rotated around its central axis whilst liquid metal poured in. Centrifuge spreads the metal over the inside surface of the mould in an even layer. Casts are normally defect free, seamless and strong. Asymmetrical moulds by the same method are pressure casts.

Reusable pressure casting - this method uses air or gas, vacuums, mechanical, or centrifugal forces to control the flow of metal into the mould. This allows the rate at which a mould fills to be more precisely controlled.

Reusable die casting - consists of a basin with molten metal, a metallic mold or die on two plates, and an injection system to draws and forces the material under pressure into the die. Cold-chamber die casts with a syringe that pushes contents into the die. Hot-chamber or gooseneck die casting immerses the chamber into the molten metal, refilling the injector, pushing the material into the mold with a piston or with air pressure. Hot-chamber systems, prone to corrosion usually use aluminium or aluminium-zinc alloys with lower melting points. Cold-chambers can be used for the higher temperatures of brass and bronze.

Continuous Casting - this process creates simple shapes, called blooms, billets, and slabs by extrusion, and is used to create the raw material for worked steel. Molten metal is fed into a funnel that control casts a simple shape, as it leaves the form it solidifies but is still pliable so it can be bent, wheels guide it horizontal to be cut.

Non-reusable sand casting - is one of the oldest methods. Runners and gates direct the metal into a mould cavity with a sand core, a vibrating table.removes the sand. It is rough and imprecise but good for large casts.

Non-reusable shell molding - sand casting with better tolerances as the sand is mixed with a resin and poured over each half of a hot metal molding pattern. This melts and cools into a shell which is brought together as a mould. These shell cores may be hollow, created in a hot metal mold in a process like slush casting. The two halves of the core mold are clamped and heated, and then filled with resin coated sand.

Non-reusable investment casting (lost-wax) - this is a precision-casting process as an alternative to sand casting that works with most grades of metal but avoids the challenges. An accurate metal die is used to cast wax or plastic patterns, which create a shell, this is covered in slurries to set, then heated releasing the wax and again to harden creating an accurate mould which will be used to cast the metal pieces.

Non-reusable full mold or foam - a combination of sand and investment cast processes using a foamed polystyrene pattern. The pattern might be removed prior to filling, or left to vaporize when hot metal is poured in. It is ideal for casting runs of one or a few pieces, but sometimes using mass-produce foam patterns.

[edit] Metalworkers

A metalsmith (also known as a smith) is one of the oldest trades and involves the heating and shaping of metal into required products, the name of the smith usually reflects either the metal being used or the products being made such as;

Blacksmiths work with iron or steel - also called Ironsmith ( farrier specifically horse shoes).

Goldsmiths work with gold ( and silver aswell as platinum and palladium).

Silver smiths work with silver.

Copper smiths work with copper and brass - also called brownsmith or brasier.

Pewtersmiths work with silver-tin alloys, also called a pewterer.

Tinsmiths work cold with tin, also called tinker, tinman, tinner, whitesmiths, or tinplate worker.

Arrowsmiths work with iron or steel making arrowheads.

Bladesmiths also called swordsmith.

Gunsmiths work with a variety of metal for weaponry.

Locksmiths work with a variety of metal for locks.

Many of the smithing trades are now less common although some such as blacksmith, locksmith and goldsmiths continue.

Today many other types of metal workers might be defined that are not related directly to the trade of smith some of these related to the processing described above such as a die caster, rivetor or welder a few examples are listed here but the list is not exhaustive;

Steelworker / Ironworker or steel erector - structural framework assemblers, working on new frames, as well as repairing and renovating old structures.

Welder- A worker who specialises in joining materials with the method by the same name metals, this includes steel, aluminium, brass, stainless steel but also varieties of plastic or polymer.

Pipe fitter-a tradesman who installs, assembles, and maintains mechanical piping systems, this involves cutting, threading, grooving, bending, and welding various pipes for sealing and continuity.

Rigger - A worker who specialises in erecting metal structures, permanent and temporary such as lighting or stage rigs.

Dry liners - A tradesman who erects and lines interior wall systems, these are commonly made from extruded aluminium.

Window framer - A fabricator who assembles window frames from different metal extrusions which can be made of alloys, aluminium and as well as steel.