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Forge

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A forge is a specialized type of hearth designed to heat metals to extreme temperatures. It can also refer to the entire workshop where this work happens, which is called a smithy.

0 typical smithy in finland
0 typical smithy in finland

The primary purpose of a forge is to make a workpiece, or the piece of metal being worked, malleable. When metal reaches a specific temperature, it becomes much easier to shape through forging. Heating also prevents work hardening, a process where metal becomes harder and more brittle as it is worked.

Muzeum Bierkowice-kuznia 1726
Muzeum Bierkowice-kuznia 1726

By controlling heat, a blacksmith can change the metallurgical properties of the metal, such as through annealing, tempering, or hardening.

To create this intense heat, a smith must carefully manage the relationship between fuel and air. Most traditional forges use bituminous coal, industrial coke, or charcoal as fuel.

Coal-forge-diagram
Coal-forge-diagram

The design relies on a hearth, which is the container for the burning fuel. A key component is the tuyere, a pipe that allows air to be forced into the fire. This air is provided by a blower or a set of bellows. When more air is introduced through the tuyere, the fuel consumes faster and burns much hotter. In a typical coal forge, the smith maintains a "coke heart," which is a ball of burning coke located in or above a firepot. The smith manages the fire's shape by surrounding the hot core with layers of unburnt coke or damp, tightly packed raw coal. This structure ensures the coal "cooks" into coke before burning directly.

There are several distinct types of forges used depending on the desired outcome. A gas forge uses propane or natural gas instead of solid fuel. These forges often feature a cylindrical chamber lined with refractory materials, such as a ceramic thermal blanket or hard castable ceramic. A burner tube mixes the gas and air, which is then ignited at the tip. While gas forges are easier for novices to use and provide a clean, consistent heat, they are less versatile than coal forges. They cannot easily be reshaped to accommodate very large or oddly shaped pieces.

Lotyšské etnografické muzeum v přírodě (17)
Lotyšské etnografické muzeum v přírodě (17)

Other specialized versions include the finery forge, which is a water-powered mill used to refine pig iron into wrought iron.

Once the metal is heated, the blacksmith uses specific tools to manipulate it. Tongs are essential for holding the hot workpiece securely; a smith may own twenty or more pairs in different shapes, such as flat, rivet, or gad tongs.

Eddystone, Pennsylvania - Railroad parts. Baldwin Locomotive Works. Blacksmith forging and hammering tools. - NARA - 518729
Eddystone, Pennsylvania - Railroad parts. Baldwin Locomotive Works. Blacksmith forging and hammering tools. - NARA - 518729

The metal is then moved to an anvil, which serves as the blacksmith's workbench. A high-quality anvil is made of cast or wrought iron with a tool steel face welded on. This steel face is vital because it provides "rebound." Rebound is the ability of the anvil to project between 50% and 99% of the hammer's energy back into the workpiece.

Anvil, labelled en
Anvil, labelled en

Anvils also feature specialized holes: the square hardy hole for holding tools and the smaller pritchel hole, which can be used as a bolster for punching holes.

Various hammers are used to strike the metal, ranging in weight from half an ounce to nearly 30 pounds. These include hand hammers like the ball-peen or cross-peen, as well as heavy sledgehammers used by a striker.

Turaidas muižas kalves darbarīki
Turaidas muižas kalves darbarīki

Other tools include fullers, which are used to create grooves or hollows, and chisels made of high carbon steel. Chisels are specifically designed with a hardened, tempered cutting edge and a softer head to prevent cracking under impact. Blacksmiths use both hot chisels for heated metal and cold chisels for working metal at room temperature.

After the shaping process, the metal often requires rapid cooling, a process known as quenching. This is done in a slack tub, which is a large container of water. Quenching can be used to harden steel or to cool the work so it can be handled by hand. In specialized tool-making or bladesmithing, this is often called a quench tank, and the smith might use oil or a salt brine instead of plain water. The term "slack" likely comes from the word "slake," meaning to slake the heat.

In modern industrial settings, forging can move beyond the handheld hammer to heavy machinery. One such method is drop forging, which uses a power hammer to shape complex parts. These hammers can be powered by hydraulics, air, or mechanics. The striking force of a drop hammer is immense, ranging from 11,000 to 425,000 pounds. The workpiece is placed between dies, and the impact forces the metal to conform to the die's shape. Sometimes, excess material is pressed out of the sides, creating what is known as flash, which is later trimmed away from the finished part.

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🖼️ Images & Media (8)
File:0 typical smithy in finland.JPG
0 typical smithy in finland.JPG
File:Muzeum Bierkowice-kuznia 1726.JPG
Muzeum Bierkowice-kuznia 1726.JPG
File:Lotyšské etnografické muzeum v přírodě (17).jpg
Lotyšské etnografické muzeum v přírodě (17).jpg
File:Coal-forge-diagram.svg
Coal-forge-diagram.svg
File:Schmiedefeuer 2.jpg
Schmiedefeuer 2.jpg
File:Anvil, labelled en.svg
Anvil, labelled en.svg
File:Turaidas muižas kalves darbarīki.jpg
Turaidas muižas kalves darbarīki.jpg
Eddystone, Pennsylvania - Railroad parts....
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