At CFI, we engineer custom screws nuts and bolts every day. One of the methods we use is called Cold Heading or Cold Forming. To answer the basic question, there is no difference between cold forming and cold heading, so the terms are truly interchangeable. The real difference is between Machining and Cold Forming. More on that later.
What is Cold Heading?
This process is creating a specified shape from a coil of metal wire using dies and punches at high speed instead of heat. This process basically feeds wire into a machine, cuts the wire into a slug and shapes the wire using high-speed hammers, dies and punches – all at room temperature. Hence the “cold” part of Cold Heading because no heat is used to create the part unlike hot forging. While this innovation was patented in the 18th century, it wasn’t put into practice until after World War II.1
Why would you utilize Cold Forming?
When compared to standard machined screws, nuts, bolts and other fasteners, cold formed parts can be extremely cost effective. The lack of heat and use of dies makes this process makes the parts creation process both energy and cost efficient when manufacturing components in large quantities.1
Cold forming is also time efficient, because you are effectively heading large quantities of parts in one shot. It produces very little raw material scrap versus machining or turning. Cold forming also adds strength to parts because the raw material does not have to be cut or heated, instead, it keeps its original structure of the metal, adding strength.
Now, there are limits. The metal is not forced beyond its tensile strength, because beyond its yield limit, fracturing would occur in the metal.
What are the basic types of Cold Forming?
There are three types of cold heading – Forward Extrusion, Backward Extrusion and Upset. Each is chosen by the material’s structural properties.
- Forward Extrusion: This direct extrusion method reduces the diameter of the original material. The material is trapped on the cavity of lesser diameter forming the head of the screw or bolt.2
- Backward Extrusion: The Backward, or Indirect Extrusion method creates hollow-shaped holes, where material flows backward around the penetrating punch.2
- Upset: Using this method, material is upset at the face of dies and can be trapped to conform to a particular shape.
Why would you utilize Machining vs. Cold Heading?
If you are creating a one-off part or prototyping a new one, cold heading is probably not the manufacturing technique that you should utilize. Cold Forming is essentially a mass production process and is capable of very high production volume because you’re essentially stamping out parts. According to Fastener Technology International Magazine, Cold Heading produces Solid Pins at 75x (300 ppm vs. 4 ppm) the rate of machining – all with considerably less scrap material.3
As a result, a company might machine parts during the prototype stage or for a lower volume product, but cold head during the mass production stage for a high-volume product.
Cold heading can hold tolerances of +/- .005″. Meanwhile, machining might hold higher tolerances (tolerances closer to +/- .0001″) because you are effectively creating one-off parts from scratch.
CFI has over 30 years of experience with both cold heading, machining and hot forging parts. We can both prototype and mass produce your components – and have been for companies ranging from automotive to aerospace to household appliances. So if you want more information about Components for Industry, our fasteners, manufacturing processes, contact us at 847-918-0333 or firstname.lastname@example.org.
1 How It Works – Cold Forming makes fasteners and a lot more – Obtained From https://todaysmachiningworld.com/magazine/how-it-works-cold-forming-makes-fasteners-and-a-lot-more/
2 Extrusion – Direct Extrusion (Forward Extrusion); Indirect Extrusion (Backward or Reverse) Obtained From https://www.egr.msu.edu/~pkwon/me477/bulkforming2.pdf
3 Cold Headed vs. Machine Sold Pins Obtained from: https://fastenertech.com/2021/02/cold-headed-vs-machined-solid-pins/