Guide
Cold Heading or CNC Turning for Custom Pins, Screws and Nuts?
Cold heading is a room-temperature forming process in which a cut length of wire or bar is struck into a die in one or more blows, so the head, shoulder or shank of a pin, screw or nut is displaced into shape instead of being cut out of bar stock. It earns its tooling on large, repeating runs; at a custom 10,000 to 20,000 pieces a year, turning on a CNC lathe is typically the safer first quote, and cold heading becomes a blank-making step only when the part is simple enough or the volume is steady enough.
By Saola Manufacturing engineering team · Published · Updated
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What is the real difference between cold heading and CNC turning?
Cold heading moves metal into shape with dedicated dies at very high rates, while CNC turning cuts the shape from bar with programmable tools and almost no dedicated tooling. One is a forming process with a high fixed cost and a low cost per piece, the other a cutting process with a low fixed cost and a higher cost per piece.
Carpenter Technology’s Heading Hints guide (2001) describes the trade from the forming side: upsetting makes the metal flow so that the grain structure follows the contour of the part, which the guide credits with better strength, toughness and fatigue resistance, whereas cutting a head out of bar cuts across the grain. Forming displaces metal rather than removing it, so little stock is lost to chips, while turning needs little dedicated tooling beyond standard tools and suits low quantities.
Today’s Machining World (2008) add that headers run at tens or hundreds of parts per minute, and Carpenter Technology’s Heading Hints guide (2001) puts the rate as high as 100 times that of machining, which is why a stable high-volume pin or screw is so much cheaper formed. The catch is everything that has to be right before the first good part: a die set, a controlled wire or slug volume, and a material that survives being struck.
At what annual volume does cold heading start to pay off?
There is no universal break-even, and the published ranges overlap the 10,000 to 20,000 a year band only at their lower edge. Treat that band as the zone where turning is the default and cold heading has to be argued for part by part.
Today’s Machining World (2008) quote one forming shop calling a couple of thousand up to about 250,000 pieces cost-effective for its mostly heavier parts, while other sources in the same article recommend hundreds of thousands to millions and warn that small quantities may not be cost-effective. Recurring orders of millions a year for small pins were reported by another shop. The spread is the lesson: where the break-even sits depends on the shop, the tooling it already owns for similar wire sizes, and the part.
The same article notes that tooling design and setup are often measured in weeks, which is much longer than programming and setting up a CNC lathe for the same part. For a buyer with a drawing that may be revised after first articles, that delay and the cost of changing dies after a revision matter as much as the unit price. A rough test: if the part number will run at a steady rate for several years and the geometry is frozen, ask for a cold-headed quote next to the turned one; if either is uncertain, turn it.
Which geometries and materials favor each process?
Cold heading favors symmetrical, rotationally simple parts with a head much larger than the shank in a heading-quality material, and CNC turning takes everything else: cross holes, grooves, tight diameters, and free-machining or exotic grades.
Carpenter Technology’s Heading Hints guide (2001) calls symmetrical parts the easiest to form and says asymmetrical parts need close cooperation between product designer and tool engineer. It also gives a controlled-upset rule of thumb: a single blow can upset only about two and a quarter wire diameters of unsupported length, and a two-blow sequence about four and a half, so a long, bulky head on a thin shank forces extra stations or a different process.
Material matters as much as shape. The sulfur that makes Type 303 stainless free-machining also makes fracture more likely during forming, and Today’s Machining World (2008) prefers heading-quality grades such as 302 HQ, with slug volume controlled to about plus or minus one percent so the die fills without flash. A drawing that calls out a free-machining grade for turning may therefore need a different grade, or a specially modified one, to be cold headed. Carpenter’s alloy tables cross-reference its stainless heading grades to ASTM A493, so the drawing or purchase order can name the wire specification as well as the grade. Side holes, internal grooves, and diameters held tighter than the formed size are cut afterward, not formed.
| Decision factor | Cold heading favored when | CNC turning favored when |
|---|---|---|
| Annual volume | Steady, repeating, in the hundreds of thousands or more | Thousands to low tens of thousands, or irregular releases |
| Design stability | Geometry frozen for years | Revisions likely after first articles |
| Geometry | Symmetrical, large head on a short shank, no cross features | Cross holes, grooves, undercuts, long slender shanks |
| Material | Heading-quality grade, annealed soft | Free-machining grades, hard or exotic alloys |
| Diameter and runout | General fastener-class diameters are enough | Critical diameters or runout set directly on the drawing |
| Tooling exposure | Dies amortized over the whole run | Little dedicated tooling to write off |
When does the hybrid route of a cold-headed blank plus CNC finish make sense?
The hybrid route makes sense when the bulk of the shape can be formed but one or two features still need cutting, because the forming removes most of the stock and the lathe handles only what a die cannot.
One example in the Today’s Machining World (2008) is a spline cut on a shaper that took minutes per part; the same blank formed in a die took seconds, and the customer finished the part by machining. The same logic applies to pins and screws: form the bulk of the shape, then add threads, cross holes and close diameters in later operations.
What the hybrid does not remove is the need for a header-capable plant. Saola runs CNC turning and milling at its lead CNC plant. If a part genuinely suits a formed blank, the forming step can be quoted through a partner plant that Saola manages, with the finish turning at the lead CNC plant and the production site of each step named on the quote. That arrangement adds a handoff, so it only pays when the volume is high enough to cover both the dies and the second step. Details of the turning side are on the CNC turning capability page.
What should you ask each supplier before you compare a heading quote with a turning quote?
Ask the same five questions of both, because a headed quote and a turned quote often price different things: one prices a part, the other a part plus dies.
First, which features are formed and which are cut afterward, so you can see the full route. Second, who owns the dies, what a revision costs, and what happens to the tooling if you move the part. Third, which grade the quote assumes, since a heading-quality grade can differ from the grade on your drawing. Fourth, which dimensions are as-headed and which are finished by turning or grinding, because Carpenter Technology’s Heading Hints guide (2001) notes that tolerances are affected by tool wear and that closer tolerances cost more. Fifth, the release pattern the price assumes, whether one large run or several smaller ones.
A quote that cannot answer these is not comparable. A cold-headed quote that quietly assumes a single annual release is not the same offer as a turned quote that assumes four.
How should the drawing be written so both processes can quote it?
Specify function, not process: call out the critical diameters, thread class, head runout and material standard, and leave non-critical surfaces unspecified so a supplier can choose forming or cutting.
Mark which dimensions are critical and which are reference, and put tolerances on the drawing per ASME Y14.5-2018 so every supplier reads the same intent. State the material by its standard designation and say whether a substitute heading-quality grade is acceptable; that single note often decides whether cold heading is even possible. Note the thread as cut or rolled only if it matters for strength or fatigue, since rolling after heading is common and cutting is the turning default.
If you are unsure which route fits, send the drawing with the annual quantity and the expected order pattern and ask for both routes priced side by side. The quoting steps are covered in the guide to preparing a machining RFQ, and the turning-side decision against Swiss-type machines is in the Swiss lathe vs CNC lathe guide.
Frequently asked
Is cold heading always cheaper than CNC turning?
No. It is cheaper per piece at high, steady volume, but the dies, setup time and revision cost can make it more expensive overall below that volume. The published volume ranges vary widely by shop, so compare total cost for the real annual quantity.
Can a cold-headed part hold the same tolerances as a turned part?
Not on every feature. Formed diameters suit standard fastener-class limits, and tolerances move with die wear, so critical diameters and runout are typically finished by turning or grinding after forming.
Are cold-headed parts stronger?
Often, because the grain flow follows the shape instead of being cut across, which the sources cited here associate with better strength and fatigue resistance. Whether it matters depends on the loaded area, so confirm it with testing for a critical fastener.
Why do some drawings make cold heading impossible?
A free-machining grade, a long thin shank under a bulky head, or cross holes and grooves can each rule out forming. Changing the grade or moving a feature to a later cutting step is sometimes enough to make it possible.
Does Saola cold head parts?
Saola runs CNC turning and milling at its lead CNC plant. A cold-forming step, where a part suits one, is quoted through a partner plant that Saola manages, with the finishing done on the lathe and each production site named on the quote.
Sources
- How It Works: Cold Forming Makes Fasteners and a Lot More, Today’s Machining World, January 2008
- Heading Hints: A Guide to Cold Forming Specialty Alloys, Carpenter Technology, 2001
- Heading (metalworking), Wikipedia, page read 2026