Cold Headed Parts
Cold headed parts are finished or stock shapes produced through a
specialized process more broadly known as cold working. Although cold
heading is a popular option, it is part of this larger group of
manufacturing processes also referred to as cold forming. As the name
would suggest, none of these techniques involve heat, but instead
materials are processed and formed at ambient temperatures. While the
name might imply that the temperature is further reduced for cold
metallurgical processes, most are carried out with machines and
materials left at room temperature.
Cold working operations include cold extrusion, cold drawing, cold roll forming, impact extrusion and orbital forming. The products of these manufacturing techniques are most commonly smaller items such as cold headed fasteners or more specifically nuts, steel pins, bolts, screws and stainless steel pins which are among the most commonly sought after implements. Many of these are made through the processing of stock forms such as cold heading wire, plate and sheet. Larger items are available, though current technology makes cold heading such products less practical than smaller and less complex objects. While cold formed steel is popular due to its strength and economic stability, other materials such as copper, aluminum, titanium, iron and brass are also processed in this manner. Although specific actions and machines vary based upon the size, material and desired outcome, most cold forming processes utilize extreme pressure to cause the plastic deformation of these metals in order to create the desired internal and external component characteristics.
Cold working processes and equipment are as variable as the many different operations they provide. Cold roll forming machines and cold headers are among the most common pieces of equipment found in a cold working shop. A roll forming machine consists of a series of rolls, commonly made of steel or roller dies. This particular type of equipment is used to produce smooth surfaced strips and sheets of precise thickness and specified cross dimensional shapes. Headers, however, offer more complex forming. While a single die, two blow header is sufficient for some cold heading applications, the production of more complex products requires shops to have a multi-die, multi blow header. This allows for a number of options as upsets, or forming can be eccentric, offset, square or elliptic. Multiple dies are used to reduce size by working the metal down smaller and smaller and also allow for the production of collars, necks, lugs, flats or fins on any point along the length of the stock shape or blank. Another popular process is what is known as cold drawing. In this process a rod is filed or hammered to a point before being placed into the die. A grip is secured to this point and then pulls the metal through the die in effect stretching it. Extrusion works in a similar manner though the materials are pushed through the die or dies rather than pulled. As is evident, dies are a common tool used in virtually every type of cold machining. These serve to confine and direct the material in order to create the desired shape and dimensions. A punch is most often used to transfer the required force from the machine to the part being created. This force must exceed the metal's elastic limit in order for the blank to undergo plastic deformation thereby permanently taking on the shape of the punch and die mechanism.
Cold working processes offer many benefits to both consumers and manufacturers. As some hot forming operations require heating large and small metallic components to astounding temperatures, cold processes offer significant energy savings. Additional economic value can be attributed to the minimization of waste materials afforded by cold working. Because the materials are altered using predominantly punch and die manufacturing, the metals are deformed and thus remain intact. Other processes such as welding, cutting and drilling on the other hand produce scraps and unused fragments of materials. While these can be recycled, this can be time consuming. Along these same lines, cold formed parts exhibit a particularly solid construction that often requires no secondary operations. Tensile strength and hardness also tend to increase as work hardening results from the repeated pressures on the part. Additionally, reproducible and consistent products can be produced even at high output rates through the use of the cold working process. One of the major differences between hot and cold forming is the tight tolerances for dimensions. Exact measurements are difficult to calibrate and reproduce with high heat applications as metal expands when warmed, but contracts when cooled. Because cold processes impact the materials at room temperature there is no expansion coefficient, meaning precision is more easily predicted and achieved.
The many benefits can be attributed to the ability of cold working to effectively create a more compact and efficient grain structure at the atomic level of the metal providing vast improvements in strength and hardness. Unfortunately this can also increase the internal strain or stress on an object. To combat this effect of cold working processes, annealing is commonly used, especially in applications requiring a number of similar or dissimilar cold working steps. Annealing allows manufacturers to soften the materials slightly in order to relieve some of the tension and improve ductility. Manufacturers often alternate cold working and annealing steps in order to create stock forms and fasteners that have the necessary permanent distortion of the crystal structure and the composition of the metal required for variable applications. Improvements to cold forming services allow for higher speed production as well as the creation of more and more complex components such as spark plugs and axles. Metallurgical and cold working advancements also increase the number of metallic elements and alloys that can be processed in this way. The versatility and simplicity of the cold forming process allows for its use and necessity in a number of industrial settings including construction, automotive, hardware, stamping, injection molding, aerospace, agriculture, recreation, furniture, electronics, pyrotechnics, packaging and upholstery. To accommodate the diverse needs of these industries, many shops offer cold working operations such as sizing, piercing, trimming, thread rolling and pointing in addition to the aforementioned processes. Cold heading service providers may also offer secondary operations such as bending, knurling, drilling, swaging, patching, tapping, shaving and milling as needed.
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Types of Cold Headed Parts
- Cold extrusion is a popular cold working process in which materials are forced through dies or around punches to produce variable lengths of cross-sectional and profile shapes.
- Cold formed steel refers to any steel components fabricated by the cold forming process.
- Cold forming is a process through which small, simple parts are produced by applying high pressure instead of heat.
are some of the most common parts that are made using cold headed
metal forming processes. These, along with screws and pins, make up
the bulk of cold headed fasteners.
- Cold headed fasteners are connective mechanisms, like screws, manufactured by the cold heading process.
are made by manufacturers of cold headed parts. These pins have a head
that is formed and shaped using the punch and die process.
hold together materials by spreading the tip via hammering and protruding
through the material.
can be made using a wide range of metal alloys. The use of a screw driver
or allen wrench is necessary for securing this type of threaded fastener.
- Cold heading wire is created through either hot or cold processes as needed to best suit the creation of cold headed parts for which it serves as the body. This wire must be suited to cold processing as well as the final use for the finished part.
- Cold heading is the process by which the heads of small, simple parts-like screws and bolts-are produced.
- Cold roll forming is a metallurgical process in which pressure is applied by a series of rollers in order to bend or form metal pieces.
- Cold working is any of a number of processes which effectively utilize the plastic deformation of materials at or near room temperature to create stock and finished parts for industrial, commercial and residential use.
- Impact extrusion is a cold forming process that produces collapsible tubes out of soft metals through impact with a punch, or ram.
- Orbital forming is a popular alternative to cold heading that offers not only fastener production possibilities, but also expands the capabilities of tooled fastening.
- Stainless steel pins are cylindrical fasteners made from a particular variety of steel alloy commonly used for its high tensile strength, durability and resistance to both heat and wear even in harsh or corrosive environments.
- Steel pins are fasteners made from steel wire that is sharpened at one end and headed at the other.
Cold Headed Parts Terms
- A compound used on the thread of fasteners to prevent the galling
of mating surfaces and improve corrosion resistance so the parts can be
- The stress
that is applied by a fastener to a joint face.
- Surfaces that are
rough or otherwise unsatisfactory, caused by a slight jumping of the tool
away from the work or the other way around.
- The force that
is exerted on the joint by the fastener.
- A fastener's
ability to hold together previously separated materials.
- The process of deforming
metal at room temperature by hammering, drawing or forming.
- The condition
in which two fastener surfaces share the same center.
- The permanent deformation
of a fastener resulting from the application of stress and heat.
The portion of the die surface that shapes the forging.
The degree of difference between the centers of a fastener's surface
at different points.
The process of forcing metal to flow through a die orifice in the same
direction in which energy is being applied (forward extrusion) or in the
reverse direction (backward extrusion), in which case the metal usually
follows the contour of the punch or moving forming tool.
- A fastener's fracture resistance ability during subjection
to variations of stress.
manipulation of wire, rod or bar stock in dies to form parts that generally
contain portions that are greater in cross-sectional area than the original
wire, rod or bar. Basically, heading is the creation of a head on a
metal part via cold form molding.
- A cavity, or series
of cavities (multiple), machined into a forging die to produce a desired
configuration in the workpiece during forging.
- A piece of steel that
is tightly fixed in a die. The insert may be used to fill a cavity, to
replace a portion of the die with a grade of steel that is better suited
for service or to function as a small die with the impression fastened
to a master die.
material(s) that the fastener connects together.
- A measurement
indicating the length between the beginning of a thread and the point
at which the thread reaches its fullest size.
- The process of
tapping a thread after plating so that its tolerances will comply within
specification and allow the internal and external threads to assemble.
- The distance between
- The immediate tension
of a fastener after tightening, which will reduce over time.
main reciprocating member of a press, guided in the press frame, to which
the punch or upper die is fastened.
part of the fastener body between the head and the threaded portion.