Guides / Processes
Cold Heading vs Machining vs Hot Forging for Custom Fasteners
September 24, 2026
Cold heading is the cheapest way to make fasteners in volume, machining is the most flexible way to make them in small lots, and hot forging is how large diameters and heavy heads get made. Most custom fasteners fit clearly into one of the three once you know the diameter and the annual volume. This guide explains how each route works and where the lines usually fall.
The short version
| Cold heading | CNC machining | Hot forging | |
|---|---|---|---|
| How it forms the part | Wire pushed through dies at room temperature | Turned from bar | Heated steel pressed in dies |
| Typical diameter | About M2 to M20 | Under M2 to M100 and beyond | About M20 to M100 and beyond |
| Typical volume | Tens of thousands and up | 1 to a few thousand | Hundreds to tens of thousands |
| Part-specific tooling | Dies and punches | Almost none | Forging dies |
| Material use | Little waste | Much of the bar becomes chips | Some flash, then machining |
| Piece price at volume | Lowest | Highest | Middle |
All values are typical. Real limits depend on the plant’s equipment.
Cold heading
Cold heading starts with wire from a coil. A former cuts a slug, then pushes it through a series of dies and punches, one station after another, to upset the head and shape the shank. A multi-station former can make a finished blank in a fraction of a second. The thread is usually rolled afterwards on a separate machine.
Why it is cheap at volume. Once the dies are made, cycle time is very short and almost all of the wire ends up in the part. Material and machine time per piece are low.
Why it is strong. The metal flows around the head instead of being cut, so the grain follows the shape of the part. Rolled threads add compressive stress at the root. Both help fatigue life, which matters for bolts under vibrating loads.
Where it struggles. Every new part needs its own dies, which take weeks to make and cost real money. Plants set up for long runs of a part, so small releases pay for setup time they barely use. Very long parts, very large diameters and some complex shapes are outside what a given former can do.
Good fit for: bolts, screws, rivets and pins in steel, stainless, brass or aluminum, from about M2 to M20, where you buy tens of thousands or more each year.
Machining
Machined fasteners are turned from bar on CNC lathes, often with live tooling for flats, cross holes and drives. Swiss-type lathes handle small diameters and long slender parts well. Threads can be cut on the lathe or rolled afterwards.
Why it is flexible. There is almost no part-specific tooling. A new part needs a program and a setup, not a set of dies. That makes machining the natural route for prototypes, small lots and parts that change often.
Why it costs more per piece. Much of the bar turns into chips, and cycle times are longer than on a former. At high volume, both add up quickly.
Rolled or cut thread. A cut thread interrupts the grain at the thread root. Rolling the thread on a machined blank keeps most of the fatigue benefit of a headed part. If the fastener carries a vibrating load, ask for rolled threads even on a machined part.
Good fit for: prototypes, lots up to a few thousand, very small or very large diameters, complex heads, tight tolerances and materials that are hard to form cold such as titanium.
Hot forging
In hot forging, bar stock is heated and pressed into dies to form the head, then machined and threaded. Heat makes the steel easier to shape, so large diameters and heavy heads become possible.
Where it wins. Diameters beyond the range of cold formers, heavy hex heads on structural bolts, anchor bolts with bends or large heads and long studs. Hot forged parts also keep good grain flow at the head.
What to expect. Forging dies cost less than a multi-station cold heading die set, and volumes can be lower. Parts need machining and thread rolling after forging and usually heat treatment to reach the grade, so lead times are longer.
Good fit for: diameters above about M20, construction and energy fasteners, heavy equipment and anything with a head too big to form cold.
Secondary operations change the picture
The forming route is only part of the cost. Most custom fasteners go through two or three more steps, and each one can move the crossover point between routes.
Thread rolling. Headed blanks are almost always rolled. Rolling is fast and adds strength, so it rarely changes the choice.
Heat treatment. Property classes 8.8 and above are quenched and tempered after forming. Cold heading plants often run their own furnaces. Machine shops usually send parts out, which adds a batch charge and a few days.
Machining after heading. Cross holes, slots, tight shoulder diameters and special points are often added to a headed blank. A part that is mostly headed with one machined feature can still be far cheaper than a fully machined one at volume.
Coating. Zinc, zinc-nickel and zinc flake coatings are usually applied in barrels or baskets, and the price per piece is similar whichever route made the part. Coating mostly affects lead time and, for high strength grades, the embrittlement precautions.
When you compare quotes from different routes, compare the finished part price including these steps, not the forming price alone.
How the choice affects your print
The route can change what is sensible to draw.
- Heads and fillets. Headed parts need a radius under the head. A sharp corner that is easy to machine can be hard to head and weakens the part.
- Tolerances. Headed and rolled features hold normal fastener tolerances easily. Very tight tolerances on a headed part may need a machining step, which adds cost.
- Thread length. Rolled threads need a short runout. If the print shows a thread up to a shoulder with no runout, only machining can make it.
- Material. Some free-machining grades do not cold head well, and some cold heading wire does not machine nicely. Let the maker suggest an equivalent.
If you are not sure which route your part suits, leave the process open on the RFQ and give the annual volume. Makers from each route will tell you where they fit.
Three examples
A flange bolt, M8 x 30, class 10.9, 200,000 pieces a year. A clear cold heading part. The dies pay for themselves in the first release and the piece price is a fraction of a machined one.
A shoulder screw with a special head, 800 pieces a year. Machining. Dies would never pay back, and the tight shoulder tolerance suits a lathe anyway.
An anchor bolt, M36 x 600, 5,000 pieces a year. Hot forged head, machined and rolled thread. Too large for a cold former and too much material to turn from bar.
A quick way to decide
- Diameter above about M20 or a very heavy head: hot forging.
- Tens of thousands per year or more, standard-looking shape: cold heading.
- Prototypes, small lots or complex shapes: machining, with rolled threads if the load is cyclic.
- In between: ask for quotes from a header and a machine shop and compare total cost, including tooling.
The grade and the coating often decide as much as the route does. Our guide to sourcing custom fasteners covers grades, coatings and first article.
For tooling, thread, heat treatment, minimum lot and lead time after the route is chosen, read the custom fastener manufacturing process.
When the print is ready, send your RFQ and we will pass it to up to three makers whose route and size range fit.
Frequently asked questions
Is a cold headed bolt stronger than a machined bolt?
Often yes, at the same material and grade. Cold heading bends the grain flow around the head instead of cutting through it, and rolled threads add compressive stress at the thread root. Both improve fatigue life. A machined bolt with a rolled thread closes much of the gap.
At what quantity does cold heading become cheaper than machining?
There is no single number. For a simple part it can be a few thousand pieces, for a complex one it may be tens of thousands. The crossover depends on die cost, cycle time and the machining time you save. Give your annual volume and let makers from both routes quote.
Can stainless steel fasteners be cold headed?
Yes. A2 and A4 stainless are cold headed every day. Stainless work hardens faster than carbon steel, so tooling wears quicker and some heads need more stations, which the maker builds into the price.
When is hot forging the only option?
When the diameter is too large for the available cold formers, the head is too heavy to form cold or the material cannot be formed cold. In practice that often means diameters above about M20 to M24 and long structural bolts.
Need this fastener made?
Send the print with the grade and annual volume. We match you with up to 3 makers that run the right route and reply within 24 business hours.
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