This article will take an in-depth look at cold heading and cold forming.
The article will bring more detail on topics such as:
In this chapter, we delve into defining cold forming, the types of materials utilized, and the different tooling methods employed in this production technique.
Cold heading, also known as cold forming, is a manufacturing technique where metal wire is shaped into specific forms without heating. This method uses high-speed hammers, dies, and punches to continuously form the metal.
The cold forming process begins by cutting a slug from a wire or coil, which is then crafted by a cold heading machine using a series of intense hammers and dies. This procedure involves exerting force from a punch onto the end of a metal blank within a die, requiring the force to exceed the metal’s yield strength to trigger plastic flow.
Viewed as a forging process absent of heat, cold heading encompasses operations like blank rolling, piercing, pointing, thread rolling, sizing, and trimming. It is pivotal for crafting metal threaded fittings and fasteners industry-wide.
As a swift forging technique, cold heading slices a wire to precise lengths at ambient temperature and under specific pressure. The cut wire then passes through consecutive die and tooling stages, transforming into a designated product, allowing shifts in feedstock diameters and lengths with operations such as piercing and trimming performing minute material adjustments in an efficient, non-stop procedure.
Originally designed for simple fastener creation, cold heading has evolved into a high-speed, automated, and multi-station method that allows for cost-effective production of composite fasteners and components. Modern cold heading accommodates tougher metals like high-temperature alloys and stainless steels.
Cold headers implement unique methodologies for slicing and gauging wire coil segments. The feeding and cutting techniques vary by machine manufacturer and utilize a cut-off knife to sever the wire from a specific angle. This process requires several components in addition to the cut-off knife.
Dies, larger than punches, sustain significant loads and are positioned on the stationary half of the cold header, typically composed of multiple pieces. The working die tool comprises three to four segments forming the whole working unit. These segments endure elevated pressure within a curved container, known as the casing, preserving the die’s lifespan over multiple cycles.
The die faces immense radial pressure per blow. Proper support averts premature failure, with the die forced tightly into the larger casing, which absorbs and spreads the pressure, ensuring die longevity through reuse before replacement.
Each die has a centered hole for part alignment. To counteract high-pressure part ejection, a knock-out pin array at the die’s rear holds the part early in the stroke, releasing it post-forming stroke. This precision system secures part removal after complete shaping.
Punches, attached to the movable section of the cold heading machine, handle less pressure than dies and are encased in punch casings despite their smaller size, managing significant loads.
Punches mold or form the screw heads, with typically one for initial and another for final impact. They also support pins pushing parts into the die, aiding trapped extrusions or recess pin accommodation, facilitating recessed part backward extrusion.
The transfer system is pivotal in cold forming, particularly in multi-die headers requiring multiple transfers. Components, like custom-designed fingers, secure parts in transit between dies, crucial for large or complex parts to avoid production defects such as head upset or shoulder droop.
Operators must precisely time the transfer to ensure secure part handling before it exits the die completely, refining this process through developed expertise.
Cold heading machines turn a metal blank into precise shapes via a reciprocating ram driving a hammer into a preformed die, often called stamping machines in manufacturing. Unaltered raw materials are then shaped as per design needs.
These machines feature bevel gears on one crankshaft end, paired with a cam gear, featuring a scissors slider on the roller shaft. The utility model fixes prior deficiencies, ensuring minimal cutting mechanism impact forces, quieter operation, and better productivity and quality.
Employing automated high-speed equipment like cold headers or part formers, the cold heading process converts simple wire into intricate components with accuracy, capable of producing up to 400 parts per minute with minimal waste.
Cold heading maintains the material’s volume, rearranging metal to form precisely designed components, ensuring efficient resource use and minimized scrap.
Recent innovations in cold forming machinery have amplified capabilities considerably. New machines with multiple dies streamline short and long part production, allowing for singular adjustments and quick setup via CNC controls. These enhancements optimize production efficiency while minimizing downtime courtesy of multi-station headers.
Contemporary cold forming merges diverse techniques for superior efficiency, and advancements in metallurgy permit forming stronger materials. Alloy producers rigorously refine compositions to meet demands for robust, corrosion-resistant parts, with controlled manufacturing of specific AISI grades for enhanced cold formability and further processing ease. Durable tool steels significantly extend die life, while versatile alloys prove valuable for machining and heading alike.
Cold heading equipment, a fundamental component in the cold heading manufacturing process, generally falls into two primary categories:
Both types of cold heading equipment utilize horizontal reciprocating rams and stationary bolsters designed to shape metal at room temperature. Cold heading machines can range from single-die setups to advanced multi-die and multi-blow machines, with some systems featuring up to seven dies in sequence. This versatility enables the production of a wide variety of fastener sizes and complex geometries, making cold heading a preferred technique in fastener manufacturing, such as for bolts, screws, rivets, and specialized custom hardware.
The production capabilities of a cold heading manufacturer depend significantly on the number and types of machines deployed in their facility. High-volume, automated cold heading machinery is particularly valuable for large-scale production runs, providing consistency, high throughput, and cost-effective mass manufacturing of precision parts.
The cold heading tooling process primarily involves two key components: dies and punches. Punches apply the necessary force from the equipment to the metal, ensuring precise dimensional control of the finished part features. Meanwhile, dies guide and shape the material into the specific form and tolerances required for the application � whether producing standard fasteners, custom cold formed parts, or intricate specialty components used in automotive, aerospace, or electronics industries.
Modern cold heading production may also incorporate auxiliary systems such as in-line wire preparation, automated material feeders, and quality inspection modules to optimize efficiency, quality, and product consistency. This ensures compliance with stringent industry specifications and customer requirements, making cold heading a go-to process for manufacturers seeking high-strength, cost-effective metal components formed without heat.
The term "cold heading" originates from the upsetting process utilized in this metal forming technique, which shapes metal at ambient temperatures for superior material properties and minimal waste.
Cold heading is the specialized technique employed to form a head on a bolt, screw, or similar fasteners by upsetting, which refers to the process of consolidating material into a specific area of the component, such as a collar or head shape. In essence, this process enlarges the diameter of the desired zone, providing structural strength to critical areas.
While upsetting may sound complex, it is a fundamental and efficient cold forming process. It begins by cutting a metal cylinder from a continuous wire coil fed into the machine. For the production of bolts and screws, or externally threaded fasteners, the raw blank is usually much longer than its diameter—enabling flexibility in the size and strength of the finished parts. Manufacturers often refer to the number of "diameters" that can be upset, indicating the degree to which material can be moved or expanded in the process.
Cold heading engineers have determined that only a specific volume of material can be upset in one operation without risking damage such as bursting or cracking. In most cold forming scenarios, this is limited to about two percent of the diameter per strike. Because many fastener heads require movement of material exceeding two diameters, multiple strokes or die stations are utilized—an essential factor in selecting between single-die, double-blow, or progressive multi-die headers.
To create complex shapes or increase the head size further, the metal blank is often processed through two or more stages (blows). Single-die solid headers typically achieve an upset of 1 to 1 1/4 diameters, while more advanced two-stroke headers can upset up to 4 1/2 diameters, with specialized equipment enabling even larger deformations in cold forming.
Calculation of the upset ratio—dividing the blank length by wire diameter—is crucial for process setup. For example, a 5-inch blank from 1/2-inch wire yields ten diameters, but only a portion of this can be upset to form the head. Exceeding the machine's capacity may result in process failures such as cold shuts, bends, or part rejection, which underscores the importance of optimal cold heading design and simulation.
Innovations in cold heading technology now allow production of high tensile and alloy steel fasteners, including parts with intricate heads or multi-step geometries. Proper selection of wire, tooling, lube, and process design ensures quality, repeatability, and extended tool life, which is essential for competitive manufacturing in sectors like automotive fasteners, aerospace components, or industrial hardware.
In cold heading, "extrusion" covers several metal forming processes used for manufacturing both solid and hollow fastener components. There are primarily three types of extrusion techniques relevant in cold forming:
In forward extrusion, the material passes forward through a die to reduce its cross-sectional area, resulting in an elongated part. This process is ideal for producing threaded rods, step-down shafts, and longer fastener blanks. Reverse extrusion, meanwhile, involves metal being forced in the opposite direction of the punch movement—creating internal features, such as recesses or holes, commonly used for making nuts, bushings, and specialty sleeves.
For example, in forward extrusion, a metal blank is driven into a smaller diameter die, increasing its length while decreasing its diameter—a controlled method of achieving precise tolerances and dimensional consistency. Reverse extrusion employs a similar principle but is focused on forming hollow features and minimizing secondary machining.
Forward extrusion is a core process for fastener manufacturers aiming to achieve optimal material flow, strength, and surface finish for parts such as screws, bolts, or stepped shafts. Reverse extrusion is favored for intricate components that require an internal cavity, such as tubular rivets or internally threaded nuts. Both processes minimize material waste by reforming rather than removing material, contributing to cost savings and sustainability in the cold forming industry.
Extrusion techniques are classified further as open or contained, each with specific capabilities and limitations influencing the geometry and strength of the finished cold headed or cold formed parts. Process selection depends on specific design requirements and end-use applications, including demand for part cleanliness, tolerance, and mechanical properties.
In open extrusion, the workpiece is not contained fully by the tooling, allowing greater extrusion length but requiring higher force. The extruding portion of the tool can be placed near the top of the die, maximizing how much material is pulled from the original blank. Open extrusion is suitable for long, slender fasteners and is commonly used in production of wire-form products and simple rod shapes.
Despite its benefits, open extrusion requires substantial pressure and adequate material support. In cold forming, insufficient support can result in buckling or deformation, particularly on highly ductile or thin materials. Proper setup, material selection, and tool design are critical for reliable, high-quality open extrusion operations.
Trapped extrusion (also called contained extrusion) involves fully enclosing the part inside the tooling before extrusion. This method allows for a higher reduction in diameter—up to approximately seventy-five percent—by applying greater compressive pressure. Contained extrusion is essential for complex shapes, stepped components, or achieving greater accuracy in final part geometry.
The drawback of trapped extrusion is the restriction on part length, as a substantial portion of the die cavity must be occupied to withstand the extrusion force. Nevertheless, this approach is ideal for manufacturing cold headed parts requiring strict control over head-to-shank relationships, thickness, and dimensional standards.
The use of a radial extrusion die, especially for contained extrusion, is common among cold headed parts manufacturers, because it reduces die pressure and encourages smooth material flow. Careful selection of wire diameter and tool configuration ensures that head dimensions and shank sizes are formed within tight tolerances, with minimal secondary machining required.
The resulting cold formed products from this process are recognized for superior mechanical properties, grain flow, and increased fatigue resistance—making trapped extrusion a preferred method for automotive, aerospace, and critical fastening applications.
Reverse extrusion is primarily utilized to create hollow fastener bodies, bushings, and precision nuts. During this process, a punch with clearance relative to the die is driven into the workpiece, forcing material backward along the punch shaft. This forms internal chambers or intricate recess features, streamlining production compared to secondary drilling or machining.
Reverse extrusion is also essential for introducing internal drive recesses in specialty fasteners and screw heads—including Phillips, Torx, or custom recesses—meeting diverse end-use requirements. As with other cold heading operations, reverse extrusion yields exceptional material utilization and metallurgical benefits, such as enhanced strength and superior thread forming capability.
Final steps in the cold heading process may include trimming and piercing: trimming removes excess material from heads or collars (e.g., for producing hex head bolts), and piercing creates through-holes or precision internal bores in nuts and bushings. These shearing processes are designed to maximize material efficiency by minimizing waste, further reducing per-part manufacturing costs and scrap rates.
Integrating trimming and piercing processes into cold heading lines enables manufacturers to produce value-engineered fasteners and custom cold formed components in a single, streamlined operation—attracting industries that prioritize quality, cost efficiency, and high production volumes, such as automotive, construction, and electronic assemblies.
This chapter will discuss the applications and benefits of cold heading forming.
The cold heading process manufactures fasteners with high efficiency and good quality, saving costs and materials. However, this process requires high quality raw materials.
Cold heading utilizes a specific grade of steel known as cold heading steel, ideal for producing fasteners and joints. Additionally, this process can be applied to tempered alloy steels, structural steels, and ferritic-martensitic duplex steels.
Cold forming offers several key benefits, including:
Cold forming is known for its rapid production capabilities, with some manufacturers achieving output rates of up to 100 parts per minute. This high-speed process ensures uniform quality and accuracy in the finished parts.
Cold forming enhances the strength of the part by maintaining the material's inherent properties. Since the material is shaped without cutting or heating, its original grain structure aligns with the part’s contours, resulting in increased durability and strength.
Unlike hot forging, the cold forming process does not require extra energy to heat the material, making it more energy-efficient.
There are several limitations associated with cold heading, including:
As the diameter of a fastener increases, the pressure needed to shape the material also rises. While large machines are capable of producing fasteners of any size, they are often not practical for such tasks. For extremely large fasteners, machining is typically the more suitable method.
Not all materials are equally suited for cold forming. While various metals can be used, selecting the most appropriate types will yield superior results and enhance the quality of the final products.
Over the years, the process of cold heading has greatly helped with improving technology and producing higher-quality machining results. Thus, when selecting cold forming for a particular process, it is vital to understand its applications, benefits, and how each cold heading approach functions.
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